Bio

Bio


Dr. Troxell is a Pathologist with special interest in breast pathology, as well as renal pathology (including medical kidney disease, kidney transplant and kidney tumors). She has been practicing pathology for over 10 years.

Clinical Focus


  • Anatomic Pathology

Academic Appointments


Administrative Appointments


  • Director, Surgical Pathology Fellowship (2016 - Present)
  • Co-Director, Post-Sophomore Fellowship (2016 - Present)

Professional Education


  • MD/PhD, Stanford University (2000)
  • Residency, Stanford University, Anatomic Pathology
  • Fellowships, Stanford University, Surgical Pathology, Renal & IPOX
  • Medical Education:Stanford University School of Medicine (2000) CA
  • Board Certification, American Board of Pathology, Anatomic Pathology (2004)

Research & Scholarship

Current Research and Scholarly Interests


Breast pathology, renal pathology with tumors, transplant; immunohistochemistry

Publications

All Publications


  • Comparison of Estrogen and Progesterone Receptor Antibody Reagents Using Proficiency Testing Data ARCHIVES OF PATHOLOGY & LABORATORY MEDICINE Troxell, M. L., Long, T., Hornick, J. L., Ambaye, A. B., Jensen, K. C. 2017; 141 (10): 1402–12

    Abstract

    - Immunohistochemical analysis of estrogen receptor (ER) and progesterone receptor (PgR) expression in breast cancer is the current standard of care and directly determines therapy. In 2010 the American Society of Clinical Oncology and the College of American Pathologists (ASCO/CAP) published guidelines for ER and PgR predictive testing, encompassing preanalytic, analytic, postanalytic factors; antibody validation; and proficiency testing.- To compare the performance of different antibody reagents for ER and PgR immunohistochemical analysis by using CAP proficiency testing data.- The CAP PM2 survey uses tissue microarrays of ten 2-mm cores per slide. We analyzed survey data from 80 ER and 80 PgR cores by antibody clone from more than 1200 laboratories.- Laboratories used the ER antibodies SP1 (72%), 6F11 (17%), 1D5 (3%), and the PgR antibodies 1E2 (61%), 16 (12%), PgR-636 (13%), PgR-1294 (8%) in 2015. While 63 of 80 ER cores (79%) were scored similarly using each of the 3 antibodies, there were significant differences for others, with SP1 yielding more positive interpretations. Four cores were scored as ER negative by more than half of the laboratories using 1D5 or 6F11, while SP1 produced positive results in more than 70% of laboratories using that antibody. Despite the greater variety of PgR antibody reagents and greater PgR tumor heterogeneity, 61 of 80 cores (76%) were scored similarly across the 4 PgR antibodies.- Accurate ER and PgR testing in breast cancer is crucial for appropriate treatment. The CAP proficiency testing data demonstrate differences in staining results by ER clone, with SP1 yielding more positive results.

    View details for DOI 10.5858/arpa.2016-0497-OA

    View details for Web of Science ID 000417030000010

    View details for PubMedID 28714765

  • TdT-positive Infiltrate in Inflamed Pediatric Kidney: A Potential Diagnostic Pitfall. American journal of surgical pathology Dunlap, J. B., Cascio, M. J., Stacey, X., Click, S., Troxell, M. L. 2017

    Abstract

    We encountered a patient with infantile nephrotic syndrome associated with a dense interstitial inflammatory infiltrate and prominent extramedullary hematopoiesis. Immunohistochemical analysis revealed numerous terminal deoxynucleotidyl transferase (TdT)-positive cells, which may raise concern for lymphoblastic lymphoma. Thus, we further characterized a group of pediatric kidneys with inflammation. TdT-positive nuclei were quantitated, and dual immunostains for TdT/CD79a, TdT/CD3, and TdT/CD43 were performed in a subset of cases; flow cytometry was performed in 1 case. TdT-positive nuclei were present in inflamed pediatric kidneys in 40 of 42 patients. TdT counts (average of 3 maximal high-power fields) ranged from 1 to >200, with a mean of 47. The presence and number of TdT-positive nuclei showed a strong association with younger patient age. Extramedullary hematopoiesis was identified in 11/42 patients, all under the age of 1. The presence of extramedullary hematopoiesis did not correlate with TdT count (P=0.158). Dual immunostaining and flow cytometric analysis in 1 case showed weak expression of B-cell markers and favored normal precursor B cells. Although TdT is a common marker of lymphoblastic lymphoma, we have demonstrated that TdT-positive cells may be part of the inflammatory milieu in infant kidneys. Together with cytologic, architectural, and clinical features, these data can help to avoid misinterpretation of involvement by lymphoblastic lymphoma/leukemia.

    View details for DOI 10.1097/PAS.0000000000000828

    View details for PubMedID 28248816

  • 'Non-classical' HER2 FISH results in breast cancer: a multi-institutional study MODERN PATHOLOGY Ballard, M., Jalikis, F., Krings, G., Schmidt, R. A., Chen, Y., Rendi, M. H., Dintzis, S. M., Jensen, K. C., West, R. B., Sibley, R. K., Troxell, M. L., Allison, K. H. 2017; 30 (2): 227-235

    Abstract

    The 2013 CAP/ASCO HER2 Testing Guidelines Update modified HER2 FISH categories such that some cases with 'monosomy', 'co-amplification/polysomy', low-level increased HER2 signals or clustered heterogeneity now are considered amplified or equivocal. This study examines the frequency and clinico-pathologic characteristics of breast cancers with equivocal or 'non-classical' HER2 FISH results. Breast cancers (2001-2014) with HER2 FISH results, HER2 immunohistochemistry, ER, grade, and age from three institutions (Stanford, UCSF, UWMC) were collected. HER2 FISH was interpreted using the updated recommendations. Amplified cases with non-classical results were grouped into the following categories: (1) 'monosomy' (ratio ≥2.0, mean HER2/cell<4.0); (2) 'co-amplified' (ratio<2.0, mean HER2/cell ≥6.0); (3) 'low amplified' (ratio ≥2.0, mean HER2/cell 4.0-5.9). Heterogeneous cases with clustered HER2-positive cells were also included. Of 8068 cases, 5.2% were equivocal and 4.6% had a 'non-classical' HER2 amplified result; 1.4% 'monosomy', 0.8% 'co-amplified', 2.1% 'low amplified', and 0.3% clustered heterogeneity. These cancers had a high frequency of ER positive (80.4%), Nottingham grade 3 (52.1%) results. The highest percentage of grade 3 cancers (66.7%) and positive HER2 immunohistochemistry (31.7%) was in the 'co-amplified' group. The 'monosomy' group had the highest percent grade 1 cancers (13.3%) and was most frequently HER2 immunohistochemistry negative (30.1%). Equivocal cases had very similar characteristics to the 'low-amplified' category. Cases with non-classical HER2 amplification or equivocal results are typically ER positive, higher grade cancers. 'Co-amplified' cases have the highest frequencies of aggressive characteristics and 'monosomy' cases the highest frequencies of lower risk features. With little clinical outcomes data currently available on these non-classical HER2 results, these results support the current classification scheme for HER2 FISH, with case-by-case correlation with additional clinical-pathologic factors when evaluating whether to offer HER2-targeted therapies in these non-classical cases.Modern Pathology advance online publication, 14 October 2016; doi:10.1038/modpathol.2016.175.

    View details for DOI 10.1038/modpathol.2016.175

    View details for Web of Science ID 000393257400007

  • HER2 Testing and Clinical Decision Making in Gastroesophageal Adenocarcinoma Guideline From the College of American Pathologists, American Society for Clinical Pathology, and American Society of Clinical Oncology ARCHIVES OF PATHOLOGY & LABORATORY MEDICINE Bartley, A. N., Washington, M. K., Ventura, C. B., Ismaila, N., Colasacco, C., Benson, A. B., Carrato, A., Gulley, M. L., Jain, D., Kakar, S., Mackay, H. J., Streutker, C., Tang, L., Troxell, M., Ajani, J. A. 2016; 140 (12): 1345-1363

    Abstract

    - ERBB2 (erb-b2 receptor tyrosine kinase 2 or HER2) is currently the only biomarker established for selection of a specific therapy for patients with advanced gastroesophageal adenocarcinoma (GEA). However, there are no comprehensive guidelines for the assessment of HER2 in patients with GEA.- To establish an evidence-based guideline for HER2 testing in patients with GEA, to formalize the algorithms for methods to improve the accuracy of HER2 testing while addressing which patients and tumor specimens are appropriate, and to provide guidance on clinical decision making.- The College of American Pathologists, American Society for Clinical Pathology, and American Society of Clinical Oncology convened an expert panel to conduct a systematic review of the literature to develop an evidence-based guideline with recommendations for optimal HER2 testing in patients with GEA.- The panel is proposing 11 recommendations with strong agreement from the open-comment participants.- The panel recommends that tumor specimen(s) from all patients with advanced GEA, who are candidates for HER2-targeted therapy, should be assessed for HER2 status before the initiation of HER2-targeted therapy. Clinicians should offer combination chemotherapy and a HER2-targeted agent as initial therapy for all patients with HER2-positive advanced GEA. For pathologists, guidance is provided for morphologic selection of neoplastic tissue, testing algorithms, scoring methods, interpretation and reporting of results, and laboratory quality assurance.- This guideline provides specific recommendations for assessment of HER2 in patients with advanced GEA while addressing pertinent technical issues and clinical implications of the results.

    View details for DOI 10.5858/arpa.2016-0331-CP.s1

    View details for Web of Science ID 000390371400007

    View details for PubMedID 27841667

  • Renal cell carcinoma in kidney allografts: histologic types, including biphasic papillary carcinoma. Human pathology Troxell, M. L., Higgins, J. P. 2016; 57: 28-36

    Abstract

    Kidney transplant recipients are at increased risk for malignancy, with about 5% incidence of cancer in native end-stage kidneys. Carcinoma in the renal allograft is far less common. Prior studies have demonstrated a propensity for renal cell carcinomas (RCCs) of papillary subtypes in end-stage kidneys, and perhaps in allograft kidneys, but most allograft studies lack detailed pathologic review and predate the current classification system. We reviewed our experience with renal carcinoma in kidney allografts at 2 academic centers applying the International Society of Urological Pathology classification, informed by immunohistochemistry. The incidence of renal allograft carcinoma was about 0.26% in our population. Of 12 allograft carcinomas, 6 were papillary (50%), 4 were clear cell (33%), 1 was clear cell (tubulo)papillary, and 1 chromophobe. Two of the papillary carcinomas had distinctive biphasic glomeruloid architecture matching the newly named "biphasic squamoid alveolar" pattern and were difficult to classify on core biopsies. The 2 cell types had different immunophenotypes in our hands (eosinophilic cells: RCC-/CK34betaE12+ weight keratin +/cyclin D1+; clear cells: RCC+/cytokeratin high molecular weight negative to weak/cyclin D1-). None of the patients experienced cancer recurrences or metastasis. Our study confirms the predilection for papillary RCCs in kidney allografts and highlights the occurrence of rare morphologic variants. Larger studies are needed with careful pathologic review, which has been lacking in the literature.

    View details for DOI 10.1016/j.humpath.2016.06.018

    View details for PubMedID 27396934

  • Multiplexed imaging reveals heterogeneity of PI3K/MAPK network signaling in breast lesions of known PIK3CA genotype. Breast cancer research and treatment Jacob, T., Gray, J. W., Troxell, M., Vu, T. Q. 2016; 159 (3): 575-583

    Abstract

    Activating genetic changes in the phosphatidylinositol-3-kinase (PI3K) signaling pathway are found in over half of invasive breast cancers (IBCs). Previously, we discovered numerous hotspot PIK3CA mutations in proliferative breast lesions. Here, we investigate the spatial nature of PI3K pathway signaling and its relationship with PI3K genotype in breast lesions.We identified PI3K phosphosignaling network signatures in columnar cell change (CCL), usual ductal hyperplasia (UDH), ductal carcinoma in situ (DCIS), and IBC in 26 lesions of known PIK3CA genotype from 10 human breast specimens using a hyperspectral-based multiplexed tissue imaging platform (MTIP) to simultaneously quantitate PI3K/MAPK pathway targets (pAKT473, pAKT308, pPRAS40, pS6, and pERK) in FFPE tissue, with single-cell resolution.We found that breast lesional epithelia contained spatially heterogeneous patterns of PI3K pathway phosphoprotein signatures, even within microscopic areas of CCL, UDH, DCIS, and IBC. Most lesions contained 3-12 unique phosphoprotein signatures within the same microscopic field. The dominant phosphoprotein signature for each lesion was not well correlated with lesion genotype or lesion histology, yet samples from the same patient tended to group together. Further, 5 UDH/CCL lesions across different patients had a common phosphosignature at the epithelial-stromal interface (possible myoepithelial cells) that was distinct from both the adjacent lesional epithelium and distinct from adjacent stroma.We present the first spatial mapping of PI3K phosphoprotein networks in proliferative breast lesions and demonstrate complex PI3K signaling heterogeneity that defies simple correlation between PIK3CA genotype and phosphosignal pattern.

    View details for DOI 10.1007/s10549-016-3962-1

    View details for PubMedID 27581127

  • Practical Applications in Immunohistochemistry Evaluation of Rejection and Infection in Organ Transplantation ARCHIVES OF PATHOLOGY & LABORATORY MEDICINE Troxell, M. L., Lanciault, C. 2016; 140 (9): 910-925

    Abstract

    Context .- Immunohistochemical analysis of tissue biopsy specimens is a crucial tool in diagnosis of both rejection and infection in patients with solid organ transplants. In the past 15 years, the concept of antibody-mediated rejection has been refined, and diagnostic criteria have been codified in renal, heart, pancreas, and lung allografts (with studies ongoing in liver, small intestine, and composite grafts), all of which include immunoanalysis for the complement split product C4d. Objectives .- To review the general concepts of C4d biology and immunoanalysis, followed by organ-allograft-specific data, and interpretative nuances for kidney, pancreas, and heart, with discussion of early literature for lung and liver biopsies. Additionally, practical applications and limitations of immunostains for infectious organisms (Polyomavirus, Adenoviridae (adenovirus), and the herpes virus family, including Herpes simplex virus, Cytomegalovirus, Human herpes virus 8, and Epstein-Barr virus) are reviewed in the context of transplant recipients. Data Sources .- Our experience and published primary and review literature. Conclusions .- Immunohistochemistry continues to have an important role in transplant pathology, most notably C4d staining in assessment of antibody-mediated rejection and assessment of viral pathogens in tissue. In all facets of transplant pathology, correlation of morphology with special studies and clinical data is critical, as is close communication with the transplant team.

    View details for DOI 10.5858/arpa.2015-0275-CP

    View details for Web of Science ID 000387047400007

    View details for PubMedID 26759930

  • Myoepithelial cells in lobular carcinoma in situ: distribution and immunophenotype. Human pathology Wang, Y., Jindal, S., Martel, M., Wu, Y., Schedin, P., Troxell, M. 2016; 55: 126-134

    Abstract

    Myoepithelial cells have important physical and paracrine roles in breast tissue development, maintenance, and tumor suppression. Recent molecular and immunohistochemical studies have demonstrated phenotypic alterations in ductal carcinoma in situ-associated myoepithelial cells. Although the relationship of lobular carcinoma in situ (LCIS) and myoepithelial cells was described in 1980, further characterization of LCIS-associated myoepithelial cells is lacking. We stained 27 breast specimens harboring abundant LCIS with antibodies to smooth muscle myosin heavy chain, smooth muscle actin, and calponin. Dual stains for E-cadherin/smooth muscle myosin heavy chain and CK7/p63 were also performed. In each case, the intensity and distribution of staining in LCIS-associated myoepithelial cells were compared with normal breast tissue on the same slide. In 78% of the cases, LCIS-associated myoepithelial cells demonstrated decreased staining intensity for one or more myoepithelial markers. The normal localization of myoepithelial cells (flat against the basement membrane, pattern N) was seen in 96% of LCIS, yet 85% of cases had areas with myoepithelial cell cytoplasm oriented perpendicular to the basement membrane (pattern P), and in 30% of cases, myoepithelial cells appeared focally admixed with LCIS cells (pattern C). This study characterizes detailed architectural and immunophenotypic alterations of LCIS-associated myoepithelial cells. The finding of variably diminished staining favors application of several myoepithelial immunostains in clinical practice. The interaction of LCIS with myoepithelial cells, especially in light of the perpendicular and central architectural arrangements, deserves further mechanistic investigation.

    View details for DOI 10.1016/j.humpath.2016.05.003

    View details for PubMedID 27195907

  • Antineoplastic Treatment and Renal Injury: An Update on Renal Pathology Due to Cytotoxic and Targeted Therapies. Advances in anatomic pathology Troxell, M. L., Higgins, J. P., Kambham, N. 2016; 23 (5): 310-329

    Abstract

    Cancer patients experience kidney injury from multiple sources, including the tumor itself, diagnostic procedures, hypovolemia, infection, and drug exposure, superimposed upon baseline chronic damage. This review will focus on cytotoxic or targeted chemotherapy-associated renal injury. In this setting, tubulointerstitial injury and thrombotic microangiopathy (vascular injury) are more common than other forms of kidney injury including glomerular. Cisplatin, pemetrexed, and ifosfamide are well-known causes of acute tubular injury/necrosis. Acute interstitial nephritis seems underrecognized in this clinical setting. Interstitial nephritis is emerging as an "immune-related adverse effect" (irAE's) with immune checkpoint inhibitors in small numbers of patients. Acute kidney injury is rarely reported with targeted therapies such as BRAF inhibitors (vemurafinib, dabrafenib), ALK inhibitors (crizotinib), and mTOR inhibitors (everolimus, temsirolimus), but additional biopsy data are needed. Tyrosine kinase inhibitors and monoclonal antibodies that block the vascular endothelial growth factor pathway are most commonly associated with thrombotic microangiopathy. Other causes of thrombotic microangiopathy in the cancer patients include cytotoxic chemotherapies such as gemcitabine and mitomycin C, hematopoietic stem cell transplant, and cancer itself (usually high-stage adenocarcinoma with marrow and vascular invasion). Cancer patients are historically underbiopsied, but biopsy can reveal type, acuity, and chronicity of renal injury, and facilitate decisions concerning continuation of chemotherapy and/or initiation of renoprotective therapy. Biopsy may also reveal unrelated and unanticipated findings in need of treatment.

    View details for DOI 10.1097/PAP.0000000000000122

    View details for PubMedID 27403615

  • Allograft pancreas: pale acinar nodules HUMAN PATHOLOGY Troxell, M. L., Drachenberg, C. 2016; 54: 127-133

    Abstract

    Microscopic pale-staining acinar nodules were characterized in native pancreas in the 1980s under a variety of names but have been infrequently reported since. We retrospectively studied the frequency and characteristics of pale acinar nodules in allograft pancreas biopsies, as compared to a sampling of native pancreas specimens at our center. Pale acinar nodules were present in 13% (9/69) of allograft biopsies from 22% (7/32) of transplant patients, and 23% (5/22) of native pancreas surgical specimens, although more nodules per pancreas area were present in allograft needle biopsies. Acinar nodules had size of 100 to 700 μm, were periodic acid-Schiff pale, were synaptophysin negative, stained more weakly with keratin CAM 5.2 compared to surrounding parenchyma, and had a low proliferative rate. Ultrastructural evaluation revealed paucity of zymogen granules with dilated cistern-like structures. In our experience, pale acinar nodules have similar features in allograft and native pancreas specimens, yet remain of uncertain etiology and significance.

    View details for DOI 10.1016/j.humpath.2016.02.029

    View details for Web of Science ID 000379990000017

    View details for PubMedID 27063474

  • Renal pathology in hematopoietic cell transplant recipients: a contemporary biopsy, nephrectomy, and autopsy series MODERN PATHOLOGY Brinkerhoff, B. T., Houghton, D. C., Troxell, M. L. 2016; 29 (6): 637-652

    Abstract

    Renal injury in hematopoietic cell transplant recipients may be related to a combination of factors including chemotherapy, radiation, infection, immunosuppressive agents, ischemia, and graft-versus-host disease, and can involve glomerular, tubulointerstitial, and vascular structures. We reviewed renal pathology from 67 patients at a single institution (2009-2014), including 14 patients with biopsy for clinical dysfunction, 6 patients with surgical kidney resection for other causes, and 47 autopsy patients. Kidney specimens frequently contained multiple histopathologic abnormalities. Thrombotic microangiopathy, membranous nephropathy, minimal change disease, and focal segmental glomerulosclerosis were the most common glomerular findings. Pathologies not previously reported in the hematopoietic cell transplant setting included collapsing glomerulopathy, antiglomerular basement membrane disease, fibrillary glomerulonephritis, and in the case of two surgical resections distinctive cellular segmental glomerular lesions that defied classification. Kidney specimens frequently demonstrated acute tubular injury, interstitial fibrosis, arteriolar hyaline, and arteriosclerosis. Other kidney findings at autopsy included leukemia and amyloid (both recurrent), diabetic nephropathy, bacterial infection, fungal invasion, and silver deposition along glomerular and tubular basement membranes. Also in the autopsy cohort, C4d immunohistochemistry demonstrated unexpected membranous nephropathy in two patients, yet C4d also colocalized with arteriolar hyaline. This retrospective hematopoietic cell transplant cohort illustrates multifaceted renal injury in patients with renal dysfunction, as well as in patients without clinically recognized kidney injury.Modern Pathology advance online publication, 25 March 2016; doi:10.1038/modpathol.2016.61.

    View details for DOI 10.1038/modpathol.2016.61

    View details for Web of Science ID 000377051600010

    View details for PubMedID 27015134

  • Cystic Neutrophilic Granulomatous Mastitis Association With Gram-Positive Bacilli and Corynebacterium AMERICAN JOURNAL OF CLINICAL PATHOLOGY Troxell, M. L., Gordon, N. T., Doggett, J. S., Ballard, M., Vetto, J. T., Pommier, R. F., Naik, A. M. 2016; 145 (5): 635-645

    Abstract

    To determine whether cystic neutrophilic granulomatous mastitis (CNGM) can be associated with Gram-positive bacilli and CorynebacteriumWe reviewed our experience with 35 granulomatous mastitis patients over a 10-year period, including histologic pattern, Gram stain and other microbiologic data, clinical presentation, treatment and outcome.Biopsies from 19 patients demonstrated CNGM, while 16 patients had other patterns of granulomatous mastitis. Gram-positive organisms were seen within microcystic spaces in 16/19 CNGM, but 0/16 non-CNGM patients (P = .000). Culture or molecular studies demonstrated Corynebacterium species in three, all CNGM. Patients with CNGM were more likely to be younger, of Hispanic ethnicity, and born outside of the United States. Granulomatous mastitis resolved after a protracted course with widely variable treatment (antibiotics, surgery, steroids).Our data further support CNGM as an infectious disease; further study of Corynebacterium-directed therapy in CNGM is needed.

    View details for DOI 10.1093/AJCP/AQW046

    View details for Web of Science ID 000377275400007

    View details for PubMedID 27247368

  • Atypical anti-glomerular basement membrane disease. Clinical kidney journal Troxell, M. L., Houghton, D. C. 2016; 9 (2): 211-221

    Abstract

    Anti-glomerular basement membrane (anti-GBM) disease classically presents with aggressive necrotizing and crescentic glomerulonephritis, often with pulmonary hemorrhage. The pathologic hallmark is linear staining of GBMs for deposited immunoglobulin G (IgG), usually accompanied by serum autoantibodies to the collagen IV alpha-3 constituents of GBMs.Renal pathology files were searched for cases with linear anti-GBM to identify cases with atypical or indolent course. Histopathology, laboratory studies, treatment and outcome of those cases was reviewed in detail.Five anti-GBM cases with atypical clinicopathologic features were identified (accounting for ∼8% of anti-GBM cases in our laboratory). Kidney biopsies showed minimal glomerular changes by light microscopy; one patient had monoclonal IgG deposits in an allograft (likely recurrent). Three patients did not have detectable serum anti-GBM by conventional assays. Three patients had indolent clinical courses after immunosuppressive treatment. One patient, untreated after presenting with brief mild hematuria, re-presented after a short interval with necrotizing and crescentic glomerulonephritis.Thorough clinicopathologic characterization and close follow-up of patients with findings of atypical anti-GBM on renal biopsy are needed. Review of the literature reveals only rare well-documented atypical anti-GBM cases to date, only one of which progressed to end-stage kidney disease.

    View details for DOI 10.1093/ckj/sfv140

    View details for PubMedID 26985371

  • Polyomavirus large T antigen is prevalent in urothelial carcinoma post-kidney transplant HUMAN PATHOLOGY Yan, L., Salama, M. E., Lanciault, C., Matsumura, L., Troxell, M. L. 2016; 48: 122-131

    Abstract

    Viral pathogens have been associated with both infectious disease and neoplasia in transplant recipients. Polyomavirus is emerging as a potential causative agent for genitourinary tract cancer in post-kidney transplant patients. Human papillomavirus (HPV) has a proven role in squamous cancers, but has not been studied in genitourinary malignancies in transplantation. Of 2345 kidney transplants performed at our center over the past 20 years, we identified 16 patients with 20 genitourinary cancers (0.7%), including 13 bladder/ureter carcinomas, 5 renal cell carcinomas (RCCs), and 2 prostate carcinomas. We performed immunohistochemical staining for polyomavirus large T antigen and p16, followed by in situ hybridization for HPV in p16+ cases. Four cases of high-grade invasive urothelial bladder carcinomas were positive for large T. Large T+ urothelial carcinomas developed at least 8 years posttransplant in young men, 3 with history of BK polyoma viremia, 2 of whom had native kidney failure due to reflux/obstruction. In situ hybridization for high-risk HPV was negative in all tested cases. Overall, 3 patients died of carcinoma. All 5 RCCs were negative for both large T and p16; 2 prostate cancers were p16 negative and p16+/HPV negative, respectively. Thus, our study shows a relatively high prevalence of large T antigen in urothelial carcinoma in kidney transplant patients (31%), but not in RCC. Although sample size is small, young patients with obstructive disease may be at particular risk for developing large T-positive urothelial carcinoma. Overall, our data further support the necessities of long-term cancer surveillance for renal transplant patients.

    View details for DOI 10.1016/j.humpath.2015.09.021

    View details for Web of Science ID 000368319200018

    View details for PubMedID 26615524

  • Myoepithelial Cell Differentiation Markers in Ductal Carcinoma in Situ Progression AMERICAN JOURNAL OF PATHOLOGY Russell, T. D., Jindal, S., Agunbiade, S., Gao, D., Troxell, M., Borges, V. F., Schedin, P. 2015; 185 (11): 3076-3089

    Abstract

    We describe a preclinical model that investigates progression of early-stage ductal carcinoma in situ (DCIS) and report that compromised myoepithelial cell differentiation occurs before transition to invasive disease. Human breast cancer MCF10DCIS.com cells were delivered into the mouse mammary teat by intraductal injection in the absence of surgical manipulations and accompanying wound-healing confounders. DCIS-like lesions developed throughout the mammary ducts with full representation of human DCIS histologic patterns. Tumor cells were incorporated into the normal mammary epithelium, developed ductal intraepithelial neoplasia and DCIS, and progressed to invasive carcinoma, suggesting the model provides a rigorous approach to study early stages of breast cancer progression. Mammary glands were evaluated for myoepithelium integrity with immunohistochemical assays. Progressive loss of the myoepithelial cell differentiation markers p63, calponin, and α-smooth muscle actin was observed in the mouse myoepithelium surrounding DCIS-involved ducts. p63 loss was an early indicator, calponin loss intermediate, and α-smooth muscle actin a later indicator of compromised myoepithelium. Loss of myoepithelial calponin was specifically associated with gain of the basal marker p63 in adjacent tumor cells. In single time point biopsies obtained from 16 women diagnosed with pure DCIS, a similar loss in myoepithelial cell markers was observed. These results suggest that further research is warranted into the role of myoepithelial cell p63 and calponin expression on DCIS progression to invasive disease.

    View details for DOI 10.1016/j.ajpath.2015.07.004

    View details for Web of Science ID 000364439000019

    View details for PubMedID 26343330

  • The New Equivocal Changes to HER2 FISH Results When Applying the 2013 ASCO/CAP Guidelines AMERICAN JOURNAL OF CLINICAL PATHOLOGY Long, T. H., Lawce, H., Durum, C., Moore, S. R., Olson, S. B., Gatter, K., Troxell, M. L. 2015; 144 (2): 253-262

    Abstract

    Human epidermal growth factor receptor 2 (HER2, ERBB2) testing is an important prognostic/predictive marker in breast cancer management, especially in selecting HER2-targeted treatment. American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) guidelines address HER2 status and were recently revised in 2013, replacing the 2007 version. For in situ hybridization interpretation, 2013 guidelines return to the prior threshold of a HER2/CEP17 ratio of 2.0 or greater for positive and eliminate 1.8 to 2.2 as the equivocal range. Also, the HER2 signal/nucleus ratio is accounted for, with 6.0 or greater for positive and 4.0 to less than 6.0 for equivocal, even in cases with a HER2/CEP17 ratio less than 2.0.With institutional review board approval, we reviewed our 2006 to 2012 HER2 fluorescence in situ hybridization (FISH) results and classified them according to both the 2007 and 2013 guidelines as negative, positive, or equivocal.Of 717 HER2 FISH results, 55 (7.7%) changed category when reassessed by 2013 guidelines. Nineteen of 25 results in the 2007 equivocal category were reassigned as positive (n = 13) or negative (n = 6). Thirty-five previously negative cases became equivocal in the 2013 scheme, 12 of these with 1+ immunohistochemistry. The positive category increased from 71 to 85.The 2013 ASCO/CAP guidelines increased the number of HER2 FISH positive and equivocal results. The equivocal group is substantially different, posing a dilemma for clinical management.

    View details for DOI 10.1309/AJCP3Q9WFOQTKUVV

    View details for Web of Science ID 000358034300008

    View details for PubMedID 26185310

  • Glomerular Endothelial Vesicles in a Renal Allograft An Unusual Pattern of Immunoglobulin Deposition in a Patient With Biclonal Gammopathy of Unknown Significance AMERICAN JOURNAL OF SURGICAL PATHOLOGY Flatley, E. M., Segal, G. M., Batiuk, T. D., Bennett, W. M., Houghton, D. C., Troxell, M. L. 2015; 39 (6): 864-869

    Abstract

    Paraproteins have varied effects on the kidney on the basis of molecular structure, concentration, and renal function. Prototypical patterns include myeloma cast nephropathy, monoclonal immunoglobulin deposition disease, and amyloid, among others. We report a 69-year-old man with end-stage diabetic nephropathy and biclonal gammopathy of unknown significance. Serum monoclonal immunoglobulin G (IgG)-κ and urine monoclonal free λ light chains were identified during workup for nephrotic syndrome. A native renal biopsy demonstrated diabetic nephropathy, without indication of paraprotein-related pathology. After transplantation, a surveillance biopsy showed endothelialitis (type 2 rejection) and abundant eosinophilic droplets, nearly occluding glomerular capillary loops. Electron microscopy localized tightly packed electron-dense vesicles in glomerular endothelial cells. Immunofluorescence studies revealed IgG-κ-dominant endothelial staining, along with λ monotypic protein resorption droplets in tubules. Two additional biopsies within the following year showed this same paraprotein distribution, with some increase in mesangial sclerosis. Two years after transplant the patient remains asymptomatic with normal creatinine levels. Literature review yields rare cases of immunoglobulin crystalline deposits in multiple glomerular cell types, rarely including endothelial cells; however, this appears to be the first report of monoclonal immunoglobulin vesicles localized solely to endothelial cells. As these vesicles were not seen in the native kidney biopsy, we hypothesize an interaction of alloimmune-mediated endothelial injury and the physiochemical properties of the IgG-κ paraprotein. In addition, this case illustrates simultaneous different patterns of accumulation of monoclonal immunoglobulin and light chain components in this unique patient with biclonal gammopathy of unknown significance.

    View details for Web of Science ID 000354485400017

    View details for PubMedID 25723111

  • Novel mutations in neuroendocrine carcinoma of the breast: possible therapeutic targets. Applied immunohistochemistry & molecular morphology Ang, D., Ballard, M., Beadling, C., Warrick, A., Schilling, A., O'Gara, R., Pukay, M., Neff, T. L., West, R. B., Corless, C. L., Troxell, M. L. 2015; 23 (2): 97-103

    Abstract

    Primary neuroendocrine carcinoma of the breast is a rare variant, accounting for only 2% to 5% of diagnosed breast cancers, and may have relatively aggressive behavior. Mutational profiling of invasive ductal breast cancers has yielded potential targets for directed cancer therapy, yet most studies have not included neuroendocrine carcinomas. In a tissue microarray screen, we found a 2.4% prevalence (9/372) of neuroendocrine breast carcinoma, including several with lobular morphology. We then screened primary or metastatic neuroendocrine breast carcinomas (excluding papillary and mucinous) for mutations in common cancer genes using polymerase chain reaction-mass spectroscopy (643 hotspot mutations across 53 genes), or semiconductor-based next-generation sequencing analysis (37 genes). Mutations were identified in 5 of 15 tumors, including 3 with PIK3CA exon 9 E542K mutations, 2 of which also harbored point mutations in FGFR family members (FGFR1 P126S, FGFR4 V550M). Single mutations were found in each of KDR (A1065T) and HRAS (G12A). PIK3CA mutations are common in other types of breast carcinoma. However, FGFR and RAS family mutations are exceedingly rare in the breast cancer literature. Likewise, activating mutations in the receptor tyrosine kinase KDR (VEGFR2) have been reported in angiosarcomas and non-small cell lung cancers; the KDR A1065T mutation is reported to be sensitive to VEGFR kinase inhibitors, and fibroblast growth factor receptor inhibitors are in trials. Our findings demonstrate the utility of broad-based genotyping in the study of rare tumors such as neuroendocrine breast cancer.

    View details for DOI 10.1097/PDM.0b013e3182a40fd1

    View details for PubMedID 25679062

  • Androgen receptor immunohistochemistry in genitourinary neoplasms INTERNATIONAL UROLOGY AND NEPHROLOGY Williams, E. M., Higgins, J. P., Sangoi, A. R., McKenney, J. K., Troxell, M. L. 2015; 47 (1): 81-85

    Abstract

    Androgen receptor (AR) is a recognized immunohistochemical marker of prostate cancer. However, the sensitivity and specificity of AR for prostate cancer in the setting of other genitourinary neoplasms has not been rigorously studied.We employed tissue microarrays containing prostate carcinomas, urothelial carcinomas, renal cell carcinomas, and testicular neoplasms. Slides were stained immunohistochemically for AR.Androgen receptor was positive in 95% of prostate carcinomas (n=230), but 19% of invasive urothelial carcinomas of the bladder (n=190) and 33% of non-invasive bladder urothelial carcinomas were also AR positive (N=107). Furthermore, 16% of renal pelvis urothelial carcinomas (n=43) were positive. Of primary renal cell carcinomas, 19% were AR positive (n=307). From a metastatic renal cell carcinoma cohort, 28% of metastases were AR positive (N=126). Six percent of non-teratomatous testicular germ cell tumors stained for AR (n=103).Our data show that the sensitivity of AR immunohistochemistry for prostate cancer is 94.8%. However, the specificity of AR is only 81.4%, among our cohort of invasive genitourinary tumors. Thus, we find the specificity of AR suboptimal, yet AR may remain useful as a component of an immunostain panel.

    View details for DOI 10.1007/s11255-014-0834-7

    View details for Web of Science ID 000347246700013

    View details for PubMedID 25218615

  • Tuberous Sclerosis-associated Renal Cell Carcinoma A Clinicopathologic Study of 57 Separate Carcinomas in 18 Patients AMERICAN JOURNAL OF SURGICAL PATHOLOGY Guo, J., Tretiakova, M. S., Troxell, M. L., Osunkoya, A. O., Fadare, O., Sangoi, A. R., Shen, S. S., Lopez-Beltran, A., Mehra, R., Heider, A., Higgins, J. P., Harik, L. R., Leroy, X., Gill, A. J., Trpkov, K., Campbell, S. C., Przybycin, C., Magi-Galluzzi, C., McKenney, J. K. 2014; 38 (11): 1457-1467

    Abstract

    Tuberous sclerosis complex (TSC) is an autosomal dominant disorder with characteristic tumors involving multiple organ systems. Whereas renal angiomyolipoma (AML) is common in TSC, renal cell carcinoma (RCC) is rarely reported. Fifty-seven RCCs from 13 female and 5 male TSC patients were reviewed. Age at surgery ranged from 7 to 65 years (mean: 42 y). Nine patients (50%) had multiple synchronous and/or metachronous RCCs (range of 2 to 20 RCCs) and 5 had bilateral RCCs (28%). Seventeen patients (94%) had histologically confirmed concurrent renal AMLs, including 15 with multiple AMLs (88%) and 9 (50%) with AMLs with epithelial cysts. None of the 15 patients with available clinical follow-up information had evidence of distant metastatic disease from 6 to 198 months after their initial surgery (mean: 52 mo). The 57 RCCs exhibited 3 major distinct morphologies: (1) 17 RCCs (30%) had features similar to tumors previously described as "renal angiomyoadenomatous tumor" or "RCC with smooth muscle stroma"; (2) 34 RCCs (59%) showed features similar to chromophobe RCC; and (3) 6 RCCs (11%) showed a granular eosinophilic-macrocystic morphology. Distinct histologic changes were also commonly present in the background kidney parenchyma and included cysts or renal tubules lined by epithelial cells with prominent eosinophilic cytoplasm, nucleomegaly, and nucleoli. Immunohistochemically, all RCCs tested showed strong nuclear reactivity for PAX8 and HMB45 negativity. Compared with sporadic RCCs, TSC-associated RCCs have unique clinicopathologic features including female predominance, younger age at diagnosis, multiplicity, association with AMLs, 3 recurring histologic patterns, and an indolent clinical course. Awareness of the morphologic and clinicopathologic spectrum of RCC in this setting will allow surgical pathologists to better recognize clinically unsuspected TSC patients.

    View details for Web of Science ID 000343880200002

    View details for PubMedID 25093518

  • Renal pathology associated with hematopoietic stem cell transplantation. Advances in anatomic pathology Troxell, M. L., Higgins, J. P., Kambham, N. 2014; 21 (5): 330-340

    Abstract

    The kidney is subject to a large variety of injurious factors before, during, and after hematopoietic stem cell transplantation (HCT), leading to a high incidence of acute kidney injury in the peritransplant period. Chronic kidney disease is estimated to impact 15% to 20% of HCT recipients. Although renal biopsies may be deferred in the setting of thrombotic microangiopathy, acute self-limited impairment, or slowly progressive functional decline, in many patients renal biopsy yields important diagnostic insight to guide treatment. Light microscopic, immunofluorescence, and ultrastructural analysis often reveals a number of concurrent abnormalities in glomeruli, tubules, interstitium, and vessels. Meta-analysis of the literature reveals that membranous nephropathy is the most commonly reported glomerular lesion in the setting of HCT, followed by minimal change disease. Autopsy and biopsy studies show that clinical criteria lack sensitivity and specificity for renal acute and chronic thrombotic microangiopathy. Viral infection and other causes of interstitial nephritis and tubular injury are important findings in HCT renal biopsies, which in many instances may not be clinically suspected. Given the complexity and variability of HCT protocols, clinicopathologic correlation is needed.

    View details for DOI 10.1097/PAP.0000000000000034

    View details for PubMedID 25105935

  • Hematopoietic stem cell transplantation: graft versus host disease and pathology of gastrointestinal tract, liver, and lung. Advances in anatomic pathology Kambham, N., Higgins, J. P., Sundram, U., Troxell, M. L. 2014; 21 (5): 301-320

    Abstract

    Hematopoietic stem cell transplantation (HCT), formerly known as bone marrow transplantation, is an integral part of treatment for many hematological malignancies. HCT is associated with several complications and comorbidities with differential effects on a wide spectrum of organs and tissues. We present an update on HCT-associated complications such as graft versus host disease (GVHD) and infection, with focus on the surgical pathology of the gastrointestinal (GI) tract, liver, and lung. Although the grading system for GI tract acute GVHD was proposed 40 years ago, recent studies have shed light on minimal histologic criteria for diagnosis of GVHD, as well as its differential diagnosis, including histologic effects of various medications. GI dysfunction in autologous transplant recipients is increasingly appreciated and patients are often biopsied. Acute liver injury in HCT is often due to sinusoidal obstruction syndrome (previously known as venoocclusive disease), or acute GVHD. Liver dysfunction at later time posttransplantation may be associated with acute or chronic GVHD, iron overload, or other causes of hepatitis. Lung injury in HCT is multifactorial, and it remains crucially important to diagnose and treat pulmonary infections. The pulmonary biopsy yields clinically unsuspected diagnoses in the majority of cases and its utilization is likely to increase. The pathology of the skin and kidney in HCT patients are detailed in accompanying articles.

    View details for DOI 10.1097/PAP.0000000000000032

    View details for PubMedID 25105933

  • Utility of Immunohistochemical Markers in Irradiated Breast Tissue An Analysis of the Role of Myoepithelial Markers, p53, and Ki-67 AMERICAN JOURNAL OF SURGICAL PATHOLOGY Anderson, K., Williams, E. M., Kaplan, J., Matsumura, L., Troxell, M. L. 2014; 38 (8): 1128-1137

    Abstract

    Radiation therapy is an important adjunct to breast-conserving surgery, but the diagnosis of recurrent/de novo carcinoma in a background of radiation atypia can be difficult, especially on small biopsies. Immunostaining for myoepithelial cell proteins is often used to assess invasion in nonirradiated breast tissue, yet these stains have not been investigated specifically in irradiated breast. We studied 29 irradiated breast resection specimens, some with carcinoma in situ (CIS, n=13) and/or invasive carcinoma (n=13). Representative blocks were stained for the myoepithelial proteins p63, smooth muscle myosin heavy chain (SMM), calponin, CK5/6, the proliferative marker Ki-67, and the tumor-suppressor p53. Nonirradiated control tissue was also stained with Ki-67 and p53 (CIS, normal, contralateral). Areas of radiation atypia/atrophy and nearly all CIS in irradiated breast tissue had abundant myoepithelial cells as evidenced by SMM, calponin, and p63 stains, with focal staining attenuation or gaps with SMM and calponin and frequently absent CK5/6 staining. As predicted, myoepithelial cell staining was absent in invasive carcinoma. p63 staining revealed postradiation myoepithelial nuclear morphologic changes. p53 staining was increased, although weak, in irradiated non-neoplastic breast (12% irradiated; 4% nonirradiated); however, irradiated CIS had less p53 staining when compared with control CIS (3% irradiated; 38% nonirradiated). As expected, Ki-67 was increased in carcinoma as compared with non-neoplastic irradiated tissue. Thus, myoepithelial immunostaining is a useful diagnostic adjunct in irradiated breast, with caveats similar to nonirradiated breast. Ki-67 may be helpful in some postradiation specimens; however, p53 staining is not reliable in this setting.

    View details for Web of Science ID 000339258600017

    View details for PubMedID 25029119

  • Frequent phosphatidylinositol-3-kinase mutations in proliferative breast lesions MODERN PATHOLOGY Ang, D. C., Warrick, A. L., Shilling, A., Beadling, C., Corless, C. L., Troxell, M. L. 2014; 27 (5): 740-750

    Abstract

    The phosphatidylinositol-3-kinase pathway is one of the most commonly altered molecular pathways in invasive breast carcinoma, with phosphatidylinositol-3-kinase catalytic subunit (PIK3CA) mutations in 25% of invasive carcinomas. Ductal carcinoma in situ (DCIS), benign papillomas, and small numbers of columnar cell lesions harbor an analogous spectrum of PIK3CA and AKT1 mutations, yet there is little data on usual ductal hyperplasia and atypical ductal and lobular neoplasias. We screened 192 formalin-fixed paraffin-embedded breast lesions from 75 patients for point mutations using a multiplexed panel encompassing 643 point mutations across 53 genes, including 58 PIK3CA substitutions. PIK3CA point mutations were identified in 31/62 (50%) proliferative lesions (usual ductal hyperplasia and columnar cell change), 10/14 (71%) atypical hyperplasias (atypical ductal hyperplasia and flat epithelial atypia), 7/16 (44%) lobular neoplasias (atypical lobular hyperplasia and lobular carcinoma in situ), 10/21 (48%) DCIS, and 13/37 (35%) invasive carcinomas. In genotyping multiple lesions of different stage from the same patient/specimen, we found considerable heterogeneity; most notably, in 12 specimens the proliferative lesion was PIK3CA mutant but the concurrent carcinoma was wild type. In 11 additional specimens, proliferative epithelium and cancer contained different point mutations. The frequently discordant genotypes of usual ductal hyperplasia/columnar cell change and concurrent carcinoma support a role for PIK3CA-activating point mutations in breast epithelial proliferation, perhaps more so than transformation. Further, these data suggest that proliferative breast lesions are heterogeneous and may represent non-obligate precursors of invasive carcinoma.

    View details for DOI 10.1038/modpathol.2013.197

    View details for Web of Science ID 000335428600012

    View details for PubMedID 24186142

  • Membranous glomerulonephritis with crescents INTERNATIONAL UROLOGY AND NEPHROLOGY Barrett, C. M., Troxell, M. L., Larsen, C. P., Houghton, D. C. 2014; 46 (5): 963-971

    Abstract

    The coexistence of membranous glomerulonephritis (MGN) and necrotizing and crescentic glomerulonephritis (NCGN) is an unusual finding in a renal biopsy except in lupus nephritis. Little is known about whether these lesions are causally related in any clinical setting.We reviewed the pathology, presentation, and clinical course of 13 non-lupus patients with combined MGN and NCGN in native kidney biopsies (nine females, four males; median age 69 years), with particular attention to evidence of secondary MGN. Additional IgG subclass and phospholipase A2 receptor (PLA2R) immunofluorescence studies were conducted in seven cases.Eight biopsies were pauci-immune other than the capillary wall deposits of MGN; one patient had a non-lupus immune complex disease, and four had mesangial deposits, including one with rare subendothelial deposits. None had anti-glomerular basement membrane disease. IgG4 was dominant or codominant in the capillary wall deposits in three cases and virtually absent in four; PLA2R was positive in two cases, and negative in five. Seven patients were judged to have secondary MGN, including five of eight ANCA+ patients. Twelve patients were treated with combinations of steroids, cyclophosphamide, rituximab, followed by durable response in seven and relentless progression to end stage renal disease in four.Secondary MGN occurs with higher frequency in ANCA-positive NCGN than in the general MGN population. A causal relationship between MGN and NCGN was not established in any patient, but circumstances suggest a common cause in several, including immune complex disease, drug reaction and paraneoplastic syndrome.

    View details for DOI 10.1007/s11255-013-0593-x

    View details for Web of Science ID 000335669300016

    View details for PubMedID 24217802

  • Frequent PIK3CA Mutations in Radial Scars DIAGNOSTIC MOLECULAR PATHOLOGY Wolters, K. L., Ang, D., Warrick, A., Beadling, C., Corless, C. L., Troxell, M. L. 2013; 22 (4): 210-214

    Abstract

    Radial scars are breast lesions of uncertain pathogenesis that are associated with a 2-fold increased risk of breast cancer compared with that in controls. Activating point mutations in PIK3CA are found in 25% to 30% of invasive breast cancers; however, they have not previously been investigated in radial scars. We sought to evaluate radial scars for known activating point mutations commonly seen in invasive breast cancer. Sixteen surgical cases containing 22 radial scars were identified from pathology archives. Lesional tissue was macrodissected from unstained paraffin sections; genomic DNA was then extracted and screened for a panel of known hotspot mutations using polymerase chain reaction and mass spectroscopy analysis. Of the 22 radial scars, 14 (63.6%) had PIK3CA mutations (10 with H1047R mutations, 2 G1049R mutations, 1 E542K, 1 E545K). The remaining 8 lesions were wild type for all of the screened genes. Of the radial scars without epithelial atypia, 9/16 (56.3%) had PIK3CA mutations; furthermore, 5/6 (83.3%) radial scars with atypia had mutations detected. In this study, the frequency of PIK3CA mutations was notably higher than the 25% to 30% mutation frequency of invasive breast cancer. This finding raises interesting questions as to the role of PIK3CA mutations in breast cancer development. Additional larger studies are indicated to confirm and extend these observations in understanding the pathogenesis of radial scars and their relationship to breast cancer.

    View details for DOI 10.1097/PDM.0b013e318288b346

    View details for Web of Science ID 000327305100005

    View details for PubMedID 24193002

  • Light Chain Renal Amyloidosis With Prominent Giant Cells AMERICAN JOURNAL OF KIDNEY DISEASES Troxell, M. L., Griffiths, R., Schnadig, I., Houghton, D. C. 2013; 62 (6): 1193-1197

    Abstract

    Clinical diagnosis of amyloidosis may be very challenging because signs, symptoms, and laboratory study results can be highly variable and may overlap with other disease entities. Amyloid has characteristic features on kidney biopsy, involving glomeruli, vessels, and/or interstitium as typically amorphous waxy material that is periodic acid-Schiff pale and Congo Red birefringent under polarized light. Electron microscopy demonstrates characteristic randomly oriented fibrils. However, in rare cases, amyloid may present with atypical morphologic features on kidney biopsy, closely mimicking other histopathologic diagnoses. We present a case of light chain (AL) κ amyloidosis with an unusual inflammatory infiltrate including prominent multinucleated giant cells in the interstitium and at the glomerular hilus. Amyloid was apparent within giant cells on Congo Red staining, as well as on ultrastructural evaluation. Together with prior studies of tumoral nonrenal amyloid and renal amyloid A, we suggest that the amyloid fibril constituents κ and serum amyloid A have some predilection for inciting the rare multinucleated giant cell reaction.

    View details for DOI 10.1053/j.ajkd.2013.05.023

    View details for Web of Science ID 000327523800026

    View details for PubMedID 23891357

  • Evolution of immunoglobulin deposition in C3-dominant membranoproliferative glomerulopathy PEDIATRIC NEPHROLOGY Kerns, E., Rozansky, D., Troxell, M. L. 2013; 28 (11): 2227-2231

    Abstract

    Complement 3 glomerulopathy (C3GN) is a newly proposed subcategory of glomerular disease with features including membranoproliferative glomerulonephritis (MPGN), C3-dominant immunofluorescent staining without appreciable immunoglobulin deposition, and electron-dense deposits. Aberrations of alternative complement pathway (AP) have been found in many C3GN patients.A 13-year-old boy presented with edema in association with an upper respiratory infection. Studies demonstrated nephrotic syndrome with hematuria and markedly low C3 and C4. Initial renal biopsy showed MPGN with strong C3 and immunoglobulin deposition. The patient partially responded to immunosuppression. Follow-up biopsies at 10 months and 3 years demonstrated MPGN with strong C3, with little to no immunoglobulin deposition. Based on this and elevated SC5b-9, treatment was changed to eculizumab with further decrease in proteinuria.Serial biopsies illustrated marked variability in immunoglobulin deposition in MPGN with persistently strong C3 deposition. Whether this evolution was related to the course of disease or to therapeutic intervention, the pathologic progression documented in this series of biopsies challenges the newly proposed subcategories of MPGN.

    View details for DOI 10.1007/s00467-013-2565-x

    View details for Web of Science ID 000325433100021

    View details for PubMedID 23892798

  • PIK3CA-AKT pathway mutations in micropapillary breast carcinoma HUMAN PATHOLOGY Flatley, E., Ang, D., Warrick, A., Beadling, C., Corless, C. L., Troxell, M. L. 2013; 44 (7): 1320-1327

    Abstract

    Micropapillary carcinoma of the breast is associated with increased rates of lymph node metastasis and lymphovascular invasion. While activating point mutations in PIK3CA (encoding phosphatidylinositol-3-kinase catalytic subunit) or AKT1 are found in 25% to 30% of invasive ductal carcinomas, the mutational profile of invasive micropapillary carcinomas has not been characterized in detail. Micropapillary carcinomas, concurrent metastatic and precursor breast lesions from 19 patients were identified. Lesional tissue was punched from paraffin-tissue blocks, and genomic DNA was extracted and screened for a large panel of known hotspot mutations using multiplex polymerase chain reaction and mass-spectroscopy analysis (643 mutations in 53 genes). Hotspot point mutations were identified in 35% (7/20) of micropapillary breast carcinomas, including PIK3CA exons 7, 9 and 20 hotspots, as well as the AKT1 plekstrin homology domain mutation (E17K); mutations in TP53 and KRAS were each found in a single patient. In 6 patients, micropapillary and non-micropapillary components of the same tumor were separately tested, yielding concordant results in five; one had a wild type micropapillary component, but a PIK3CA mutation in the invasive ductal component. Concurrent lymph node metastases were mostly wild type (2/8 mutant). Accompanying ductal carcinoma in situ had point mutations in 45% (5/11), mostly concordant with invasive carcinoma; however, mutational status of other breast proliferative lesions was generally discordant with accompanying carcinoma. The rate of PIK3CA mutations in this series of micropapillary carcinomas is similar to invasive ductal carcinomas; however, there may be an enrichment of AKT1 mutations (10%). The non-micropapillary components and precursor lesions occasionally had different mutations.

    View details for DOI 10.1016/j.humpath.2012.10.018

    View details for Web of Science ID 000321225000014

    View details for PubMedID 23352210

  • Novel Method for PIK3CA Mutation Analysis Locked Nucleic Acid-PCR Sequencing JOURNAL OF MOLECULAR DIAGNOSTICS Ang, D., O'Gara, R., Schilling, A., Beadling, C., Warrick, A., Troxell, M. L., Corless, C. L. 2013; 15 (3): 312-318

    Abstract

    Somatic mutations in PIK3CA are commonly seen in invasive breast cancer and several other carcinomas, occurring in three hotspots: codons 542 and 545 of exon 9 and in codon 1047 of exon 20. We designed a locked nucleic acid (LNA)-PCR sequencing assay to detect low levels of mutant PIK3CA DNA with attention to avoiding amplification of a pseudogene on chromosome 22 that has >95% homology to exon 9 of PIK3CA. We tested 60 FFPE breast DNA samples with known PIK3CA mutation status (48 cases had one or more PIK3CA mutations, and 12 were wild type) as identified by PCR-mass spectrometry. PIK3CA exons 9 and 20 were amplified in the presence or absence of LNA-oligonucleotides designed to bind to the wild-type sequences for codons 542, 545, and 1047, and partially suppress their amplification. LNA-PCR sequencing confirmed all 51 PIK3CA mutations; however, the mutation detection rate by standard Sanger sequencing was only 69% (35 of 51). Of the 12 PIK3CA wild-type cases, LNA-PCR sequencing detected three additional H1047R mutations in "normal" breast tissue and one E545K in usual ductal hyperplasia. Histopathological review of these three normal breast specimens showed columnar cell change in two (both with known H1047R mutations) and apocrine metaplasia in one. The novel LNA-PCR shows higher sensitivity than standard Sanger sequencing and did not amplify the known pseudogene.

    View details for DOI 10.1016/j.jmoldx.2012.12.005

    View details for Web of Science ID 000318755200004

    View details for PubMedID 23541593

  • Enteric Oxalate Nephropathy in the Renal Allograft: An Underrecognized Complication of Bariatric Surgery AMERICAN JOURNAL OF TRANSPLANTATION Troxell, M. L., HOUGHTON, D. C., Hawkey, M., Batiuk, T. D., Bennett, W. M. 2013; 13 (2): 501-509

    Abstract

    Enteric hyperoxalosis is a recognized complication of bariatric surgery, with consequent oxalate nephropathy leading to chronic kidney disease and occasionally end-stage renal failure. In patients with prior gastrointestinal bypass surgery, renal allografts are also at risk of oxalate nephropathy. Further, transplant recipients may be exposed to additional causes of hyperoxalosis. We report two cases of renal allograft oxalate nephropathy in patients with remote histories of bariatric surgery. Conservative management led to improvement of graft function in one patient, while the other patient returned to dialysis. Interpretation of serologic, urine and biopsy studies is complicated by oxalate accumulation in chronic renal failure, and heightened excretion in the early posttransplant period. A high index of suspicion and careful clinicopathologic correlation on the part of transplant nephrologists and renal pathologists are required to recognize and treat allograft oxalate nephropathy. As the incidence of obesity and pretransplant bariatric surgery increases in the transplant population, allograft oxalate nephropathy is likely to be an increasing cause of allograft dysfunction.

    View details for DOI 10.1111/ajt.12029

    View details for Web of Science ID 000314171100035

    View details for PubMedID 23311979

  • Mucinous breast carcinomas lack PIK3CA and AKT1 mutations HUMAN PATHOLOGY Kehr, E. L., Jorns, J. M., Ang, D., Warrick, A., Neff, T., Degnin, M., Lewis, R., Beadling, C., Corless, C. L., Troxell, M. L. 2012; 43 (12): 2207-2212

    Abstract

    Activating point mutations in the phosphatidylinositol-3-kinase catalytic subunit (PIK3CA) are among the most common molecular defects in invasive breast cancer. Point mutations in the downstream kinase AKT1 are seen in a minority of carcinomas. These mutations are found preferentially in estrogen receptor-positive and Her2-positive breast carcinomas; however, special morphologic types of breast cancer have not been well studied. Twenty-nine cases of pure invasive mucinous carcinoma and 9 cases of ductal carcinoma with mucinous differentiation were screened for a panel of point mutations (>321 mutations in 30 genes) using a multiplex polymerase chain reaction panel with mass spectroscopy readout. In addition, associated ductal carcinoma in situ, hyperplasia, or columnar cell lesions were separately tested where available (25 lesions). In 3 invasive cases and 15 ductal carcinoma in situ/proliferative lesions, PIK3CA hotspot mutations were, instead, tested by direct sequencing. No point mutations were identified in invasive mucinous breast carcinoma. This contrasts with the 35% frequency of PIK3CA mutations in a comparative group of invasive ductal carcinomas of no special type. Interestingly, PIK3CA hotspot point mutations were identified in associated ductal carcinoma in situ (3/14) and hyperplasia (atypical ductal hyperplasia [2/3], usual ductal hyperplasia [2/3], columnar cell change [1/5]), suggesting that PIK3CA mutations may play a role in breast epithelial proliferation. This series represents the largest study, to date, of PIK3CA genotyping in mucinous carcinoma and supports the unique pathogenetics of invasive mucinous breast carcinoma.

    View details for DOI 10.1016/j.humpath.2012.03.012

    View details for Web of Science ID 000311762500013

    View details for PubMedID 22705004

  • Phosphatidylinositol-3-kinase pathway mutations are common in breast columnar cell lesions MODERN PATHOLOGY Troxell, M. L., Brunner, A. L., Neff, T., Warrick, A., Beadling, C., Montgomery, K., Zhu, S., Corless, C. L., West, R. B. 2012; 25 (7): 930-937

    Abstract

    The phosphatidylinositol-3-kinase pathway is one of the most commonly mutated pathways in invasive breast carcinoma, with PIK3CA mutations in ∼25% of invasive carcinomas, and AKT1 mutations in up to 5%. Ductal carcinoma in situ, and benign papillomas harbor similar mutations. However, activating point mutations in breast columnar cell lesions have been infrequently studied. Twenty-three breast resection specimens containing columnar cell lesions were identified; 14 with associated invasive carcinoma or carcinoma in situ. DNA extracts were prepared from formalin-fixed paraffin-embedded tissue and screened for a panel of point mutations (321 mutations in 30 genes) using a multiplex PCR panel with mass-spectroscopy readout. PIK3CA mutations were identified in 13/24 columnar cell lesions (54%) and 3/8 invasive carcinomas (37%). The mutation status of columnar cell lesions and associated carcinoma was frequently discordant. Of the 14 cases, only 5 demonstrated the same genotype in matched samples of columnar cell lesions and carcinoma (4 wild type, 1 PIK3CA H1047R). Interestingly, five patients had mutations in columnar cell lesions with wild-type carcinoma; two patients had different point mutations in columnar cell lesions and carcinoma. Only three cases had wild-type columnar cell lesion and mutated carcinoma. The 50% PIK3CA mutation prevalence in columnar cell lesions is greater than reported in most studies of invasive breast cancer. Further, columnar cell lesions and carcinoma were frequently discordant for PIK3CA/AKT1 mutation status. These findings raise interesting questions about the role of PIK3CA/AKT pathway in breast carcinogenesis, and the biologic/precursor potential of columnar cell lesions.

    View details for DOI 10.1038/modpathol.2012.55

    View details for Web of Science ID 000306106600002

    View details for PubMedID 22460814

  • Patterns of IgG Subclass Deposits in Membranous Glomerulonephritis in Renal Allografts TRANSPLANTATION PROCEEDINGS Kearney, N., Podolak, J., Matsumura, L., Houghton, D., Troxell, M. 2011; 43 (10): 3743-3746

    Abstract

    Membranous glomerulonephritis (MGN) may develop in the renal allograft either de novo or as a recurrence. These 2 forms of MGN may have different pathogenic mechanisms, with different IgG subclass profiles in the immune deposits. This study examined IgG subclass distributions in recurrent and de novo MGN in allograft kidneys.We identified allograft kidneys with MGN, including 7 with recurrent MGN, 2 with de novo MGN, and 2 atypical/indeterminate, and determined the relative intensity of IgG1, IgG2, IgG3, and IgG4 staining in capillary wall deposits by immunofluorescence microscopy.IgG4 was the dominant or codominant IgG subclass in capillary loop deposits in all 7 cases of recurrent MGN. IgG1 staining was dominant in 3 of 4 de novo or atypical MGN cases and codominant with IgG4 in the fourth.Although pretransplantation kidney biopsies were not available for comparisons, these findings suggest that all allograft recurrences represent idiopathic MGN and that de novo MGN cases had a different pathogenic mechanism.

    View details for DOI 10.1016/j.transproceed.2011.10.042

    View details for Web of Science ID 000298620200032

    View details for PubMedID 22172838

  • An abundance of IgG4+plasma cells is not specific for IgG4-related tubulointerstitial nephritis MODERN PATHOLOGY Houghton, D. C., Troxell, M. L. 2011; 24 (11): 1480-1487

    Abstract

    IgG4-related tubulointerstitial nephritis (IgG4-TIN), the renal parenchymal lesion of IgG4-related sclerosing disease, is characterized, among other things, by the presence of numerous IgG4-positive plasma cells (IgG4+PC) in the kidney infiltrate. The specificity of this finding for IgG4-TIN has not been addressed. To address this we examined 100 consecutive renal biopsy samples with active interstitial inflammation for the presence of IgG4+PC, and correlated the findings with principal diagnosis, the available clinical histories, and the findings in four biopsy samples of IgG4-TIN. Eleven of the survey biopsy samples contained an average of more than 10 IgG4+PC per × 200 field, including two with IgG4+PC in numbers comparable to those in two of the IgG4-related tubulointerstitial disease biopsy samples. The principal pathological diagnoses in the IgG4+PC-rich cases included anti-neutrophil cytoplasmic antibody-positive necrotizing glomerulonephritis (five cases), diabetic nephropathy (two cases), idiopathic interstitial nephritis (two cases), membranous glomerulonephritis (one case), and lupus nephritis (one case). There was no reason, based on histology or clinical history, to believe that any of these cases represented previously unsuspected IgG4-related tubulointerstitial disease. We conclude that the presence of numerous IgG4+PC is essential to, but not sufficient for, the diagnosis of IgG4-TIN.

    View details for DOI 10.1038/modpathol.2011.101

    View details for Web of Science ID 000296739000008

    View details for PubMedID 21701536

  • Guidelines for the Diagnosis of Antibody-Mediated Rejection in Pancreas Allografts-Updated Banff Grading Schema AMERICAN JOURNAL OF TRANSPLANTATION Drachenberg, C. B., Torrealba, J. R., Nankivell, B. J., Rangel, E. B., Bajema, I. M., Kim, D. U., Arend, L., Bracamonte, E. R., Bromberg, J. S., Bruijn, J. A., Cantarovich, D., Chapman, J. R., Farris, A. B., Gaber, L., Goldberg, J. C., Haririan, A., Honsova, E., Iskandar, S. S., Klassen, D. K., Kraus, E., Lower, F., Odorico, J., Olson, J. L., Mittalhenkle, A., Munivenkatappa, R., Paraskevas, S., Papadimitriou, J. C., Randhawa, P., Reinholt, F. P., Renaudin, K., Revelo, P., Ruiz, P., Samaniego, M. D., Shapiro, R., Stratta, R. J., Sutherland, D. E., Troxell, M. L., Voska, L., Seshan, S. V., Racusen, L. C., Bartlett, S. T. 2011; 11 (9): 1792-1802

    Abstract

    The first Banff proposal for the diagnosis of pancreas rejection (Am J Transplant 2008; 8: 237) dealt primarily with the diagnosis of acute T-cell-mediated rejection (ACMR), while only tentatively addressing issues pertaining to antibody-mediated rejection (AMR). This document presents comprehensive guidelines for the diagnosis of AMR, first proposed at the 10th Banff Conference on Allograft Pathology and refined by a broad-based multidisciplinary panel. Pancreatic AMR is best identified by a combination of serological and immunohistopathological findings consisting of (i) identification of circulating donor-specific antibodies, and histopathological data including (ii) morphological evidence of microvascular tissue injury and (iii) C4d staining in interacinar capillaries. Acute AMR is diagnosed conclusively if these three elements are present, whereas a diagnosis of suspicious for AMR is rendered if only two elements are identified. The identification of only one diagnostic element is not sufficient for the diagnosis of AMR but should prompt heightened clinical vigilance. AMR and ACMR may coexist, and should be recognized and graded independently. This proposal is based on our current knowledge of the pathogenesis of pancreas rejection and currently available tools for diagnosis. A systematized clinicopathological approach to AMR is essential for the development and assessment of much needed therapeutic interventions.

    View details for DOI 10.1111/j.1600-6143.2011.03670.x

    View details for Web of Science ID 000294360400007

    View details for PubMedID 21812920

  • PAX2 Expression in Wilms Tumors and Other Childhood Neoplasms AMERICAN JOURNAL OF SURGICAL PATHOLOGY Davis, J. L., Matsumura, L., Weeks, D. A., Troxell, M. L. 2011; 35 (8): 1186-1194

    Abstract

    PAX2 plays an important role in kidney development; although small studies have demonstrated PAX2 expression in Wilms tumors (WT), comprehensive studies on formalin-fixed tissue are lacking. Thus, we systematically evaluated PAX2 immunohistochemical staining in a retrospective study of pediatric WT, as compared with other pediatric tumors. We stained formalin-fixed, paraffin-embedded sections from 39 WT, 6 nephrogenic rests, 8 non-Wilms renal tumors, and 43 nonrenal pediatric small round cell tumors with 2 different PAX2 polyclonal antibodies. PAX2 demonstrated strong, diffuse staining of epithelial and blastema components of WT (97% of cases). PAX2 stained WT stroma in fewer cases (23%), but 80% of anaplastic foci were positive. Nephrogenic rests, 1 case of metanephric adenoma, and 1 pediatric renal cell carcinoma were also PAX2 positive; other pediatric renal tumors were negative. Neuroblastoma, primitive neuroectodermal tumor/Ewings, and T-cell acute lymphoblastic lymphoma (ALL) were PAX2 negative. However, PAX2 weakly stained some cases of B-cell ALL rhabdomyosarcoma (RMS) was also stained, especially alveolar RMS (83%), with less staining of embryonal RMS (13%). One of the antibodies also stained maturing myoid cytoplasm of WT and RMS. This study shows that PAX2 is a sensitive marker of WT (sensitivity 97%), but PAX2 shows weak-to-moderate-intensity nuclear staining of RMS and B-cell ALL, somewhat limiting its utility. However, PAX2 may be a helpful marker in certain diagnostic situations. We speculate that RMS and B-cell ALL staining could be due to antibody cross-reactivity with PAX family members with known expression in RMS and B-cell ALL.

    View details for DOI 10.1097/PAS.0b013e31821d3131

    View details for Web of Science ID 000292728200013

    View details for PubMedID 21730820

  • Acute kidney injury with cryoglobulinemic peritubular neutrophilic capillaritis CLINICAL NEPHROLOGY Troxell, M. L., Shackleton, D. V., Raguram, P., HOUGHTON, D. C. 2011; 76 (2): 159-165

    Abstract

    Neutrophil predominant capillaritis and interstitial inflammation is an uncommon renal biopsy finding, with a broad differential diagnosis.A 77-year-old woman presented with a complicated history including vasculitis, cryoglobulinemia, malaise, and systemic symptoms, which progressed to acute kidney injury. Renal biopsy demonstrated prominent neutrophilic capillaritis with interstitial inflammation, and fibrinoid deposits in medullary capillaries and interstitium. Glomeruli showed membranoproliferative glomerulonephritis, but no crescents or necrosis.We interpret the capillary and interstitial changes as evidence of cryoglobulin-associated vasculitis, and discuss the differential diagnosis of this uncommon histologic pattern of renal pathology, including other vasculitides, infection, ischemia-infarction, collagen vascular disease, and antibody-mediated allograft rejection, among others.

    View details for DOI 10.5414/CN106626

    View details for Web of Science ID 000294364500012

    View details for PubMedID 21762649

  • Immunohistochemical and Molecular Markers in Breast Phyllodes Tumors APPLIED IMMUNOHISTOCHEMISTRY & MOLECULAR MORPHOLOGY Korcheva, V. B., Levine, J., Beadling, C., Warrick, A., Countryman, G., Olson, N. R., Heinrich, M. C., Corless, C. L., Troxell, M. L. 2011; 19 (2): 119-125

    Abstract

    Phyllodes tumors of the breast are diagnostically and managerially enigmatic, as their malignant potential is difficult to predict based on the standard morphologic criteria. Thus, there is a need for additional markers of biologic potential. Although a number of ancillary tests have been reported, consensus in the literature is lacking. We studied 38 cellular fibroadenomas and phyllodes tumors of various grade (World Health Organization benign, borderline, and malignant) with a panel of immunohistochemical stains (p53, CD117, phospho-Histone3, mdm2, cdk4) and screened 26 of the tumors for mutations across 30 cancer-related genes using PCR and mass-spectrometry based methods. p53 and phospho-Histone3 (mitotic marker) showed increased staining in higher grade phyllodes tumors. CD117, mdm2, and cdk4 showed no difference in expression across different grades of phyllodes tumors. Mutational analysis revealed an S8R substitution in FBX4 (an E3 ubiquitin ligase) in 3 cases: 1 benign and 2 borderline. The S8R substitution seems to be more common in phyllodes tumors (11.5%) as compared with other cancers. FBX4 S8R cases had high cyclin D1 expression, but this finding was not specific. Our data support earlier studies showing that p53 has potential use in pathologic assessment of phyllodes tumors, and we newly characterized phospho-Histone3 for this application. Further studies are needed to characterize the molecular pathogenesis of the phyllodes tumors, as we were unable to identify activating mutations despite screening for a large panel of activating hotspot mutations. The significance of the FBX4 substitution deserves further investigation.

    View details for DOI 10.1097/PAI.0b013e3181f5349a

    View details for Web of Science ID 000287190000006

    View details for PubMedID 21030860

  • Glomerular fibrin thrombi in ABO and crossmatch compatible renal allograft biopsies PATHOLOGY RESEARCH AND PRACTICE Troxell, M. L., Norman, D., Mittalhenkle, A. 2011; 207 (1): 15-23

    Abstract

    Glomerular fibrin thrombi may be an early indication of antibody-mediated rejection in renal allograft biopsies. However, fibrin thrombi have a broad differential; thus, we sought to evaluate the etiology and implications of glomerular fibrin thrombi in allograft biopsies of blood group and cytotoxic crossmatch compatible renal allografts. Biopsies were identified from the pathology files of Oregon Health & Science University. Detailed histopathologic findings were retrospectively correlated with clinical data, treatment, and outcome. Sixteen early posttransplant biopsies had glomerular fibrin thrombi, including three surveillance biopsies. Six of 16 biopsies had no other histopathologic findings; 5/16 had glomerulitis and peritubular capillaritis; 4/16 had concomitant cellular vascular rejection; one had parenchymal infarction. C4d staining was positive in 4/16 cases. Most patients were treated with IVIg and plasmapheresis, others with rapamycin, thymoglobulin, or rituximab. At an average follow-up of 62 months, 8 patients with functioning grafts had a mean serum creatinine of 1.4 mg/dL (122 μmol/L). Antibody-mediated rejection is an important consideration in blood group compatible allograft biopsies with glomerular fibrin thrombi, even with C4d-negative biopsies. However, multidisciplinary evaluation is necessary, given other etiologies, including drug toxicity, hemolytic-uremia syndrome, and large vessel thrombosis. Despite aggressive treatment, both short and long-term graft survival may be compromised.

    View details for DOI 10.1016/j.prp.2010.10.001

    View details for Web of Science ID 000286917600003

    View details for PubMedID 21067871

  • Distinctive Morphology of Renal Cell Carcinomas in Tuberous Sclerosis INTERNATIONAL JOURNAL OF SURGICAL PATHOLOGY Schreiner, A., Daneshmand, S., Bayne, A., Countryman, G., Corless, C. L., Troxell, M. L. 2010; 18 (5): 409-418

    Abstract

    Tuberous sclerosis complex results from mutations in 1 of 2 interacting gene products, hamartin or tuberin. The syndrome is characterized by hamartomas and neoplastic lesions, including angiomyolipomas of the kidney and other organs. Renal cell carcinoma (RCC) in tuberous sclerosis remains relatively poorly characterized because historical studies were confounded by the inclusion of epithelioid angiomyolipomas. The authors present a patient with tuberous sclerosis and bilateral renal lesions, including multiple minute angiomyolipomas, cortical cysts, and 4 separate RCCs of unclassified type. The carcinomas shared distinctive morphological features, including sheet-like, glandular, trabecular, or cystic architecture and abundant granular eosinophilic cytoplasm. By definition, the carcinomas were keratin positive and negative for HMB-45 and Melan-A. Detailed immunohistochemical analysis revealed heterogeneity among the cortical cysts and carcinomas. The histopathological features of these carcinomas illustrate characteristics of renal carcinoma that are probably related to genetic alterations of tuberous sclerosis.

    View details for DOI 10.1177/1066896909333510

    View details for Web of Science ID 000281768300023

    View details for PubMedID 19403547

  • Pancreas Allograft Rejection: Analysis of Concurrent Renal Allograft Biopsies and Posttherapy Follow-Up Biopsies TRANSPLANTATION Troxell, M. L., Koslin, D. B., Norman, D., Rayhill, S., Mittalhenkle, A. 2010; 90 (1): 75-84

    Abstract

    Pancreas and kidney allograft function is routinely monitored with serum studies (amylase, lipase, and creatinine). Increased levels commonly prompt tissue biopsy, to diagnose cause of graft dysfunction. Historically, pancreas allografts were infrequently biopsied, although serum enzymes and renal rejection may be poor surrogates for pancreas status.Pancreas allograft biopsies at our center were reviewed and reclassified according to University of Maryland (UMD) and Banff criteria; C4d immunostaining was performed. Findings were correlated with clinical data and renal allograft biopsies.Fifty-six pancreas allograft biopsies from 27 patients were evaluated. UMD and Banff grading were similar, although two UMD "indeterminate" biopsies were Banff grade 1 rejection. There were 21 concurrent pancreas and renal biopsies, all from simultaneous pancreas-kidney allograft recipients. Thirteen pairs were concordant for rejection; eight pairs were discordant for rejection (38%); six pairs showed pancreas rejection without kidney rejection, and two pairs showed the converse. Fourteen patients had a total of 21 follow-up pancreas allograft biopsies. Seven biopsies showed a lower grade of rejection on follow-up biopsy, 4 biopsies showed more severe rejection, and 10 had unchanged grade. In only 9 of these 21 (43%) cases, did the interval serum amylase or lipase trend parallel the subsequent biopsy diagnosis.With a high biopsy discordance rate, our data suggest that renal allograft rejection is a poor surrogate for pancreas allograft status. Likewise, serum amylase and lipase levels do not predict response to rejection therapy. Surveillance or posttherapy pancreas allograft biopsies may be a useful means to monitor pancreas allograft status.

    View details for DOI 10.1097/TP.0b013e3181dda17e

    View details for Web of Science ID 000279644400011

    View details for PubMedID 20548259

  • Glomerular basement membrane lipidosis in Alagille syndrome PEDIATRIC NEPHROLOGY Davis, J., Griffiths, R., Larkin, K., Rozansky, D., Troxell, M. 2010; 25 (6): 1181-1184

    Abstract

    Alagille syndrome is characterized by a paucity of interlobular bile ducts with chronic cholestasis, cardiac, skeletal, and eye abnormalities and is associated predominantly with JAG1 mutations. Various renal abnormalities have been sporadically described. The classic renal histopathology described in Alagille syndrome is mesangiolipidosis, with lipid deposits predominately confined to the mesangium and minimal deposition within the glomerular basement membrane (GBM). We report a 5-year-old girl with Alagille syndrome who presented with persistent subnephrotic proteinuria and renal tubular acidosis. A renal biopsy showed GBM irregularities (mimicking membranous glomerulonephritis), mesangial sclerosis, and focal segmental glomerulosclerosis (FSGS) on light microscopy. Electron microscopy revealed few lipid inclusions within the mesangium but extensive inclusions along the GBM. These findings are mostly consistent with those reported previously in Alagille syndrome. However, the histologic distribution of lipid vacuoles is seemingly reversed in this patient and is uniquely accompanied by FSGS, emphasizing the spectrum of renal histopathology seen in Alagille syndrome. The proteinuria observed in this patient is likely attributed to significant GBM lipid deposition, which over time may contribute to the development of FSGS.

    View details for DOI 10.1007/s00467-009-1426-0

    View details for Web of Science ID 000276745600024

    View details for PubMedID 20091053

  • Factors influencing accuracy of axillary sentinel lymph node frozen section for breast cancer 96th Annual Meeting of the North-Pacific-Surgical-Association Jensen, A. J., Naik, A. M., Pommier, R. F., Vetto, J. T., Troxell, M. L. EXCERPTA MEDICA INC-ELSEVIER SCIENCE INC. 2010: 629–34

    Abstract

    Intraoperative sentinel lymph node (SLN) frozen section (FS) guides immediate axillary lymph node dissection in breast cancer patients.The Oregon Health & Science University pathology database was searched for SLN FS From October 1999 to January 1, 2009. Slides of positive cases were reviewed and metastasis sizes measured.Of 416 cases, 129 were positive (31%) on permanent sections and immunohistochemistry, with 79 concordant and 50 false-negative FS. Accuracy was 88%, sensitivity 61%, and specificity 100%. FS accuracy for lobular carcinoma (76%) was lower than for invasive ductal carcinoma (88%) (P = .048). FS accuracy significantly differed by size of nodal tumor. For 49 cases of tumor 2-mm metastases, accuracy was 90% (P < .0001).False-negative FS were predominantly small nodal tumor deposits not sampled at FS. Although accuracy was lower, SLN FS is still beneficial in lobular carcinoma, but not ductal carcinoma in situ.

    View details for DOI 10.1016/j.amjsurg.2010.01.017

    View details for Web of Science ID 000278352600018

    View details for PubMedID 20466107

  • Phosphatidylinositol-3-kinase and AKT1 mutations occur early in breast carcinoma BREAST CANCER RESEARCH AND TREATMENT Dunlap, J., Le, C., Shukla, A., Patterson, J., Presnell, A., Heinrich, M. C., Corless, C. L., Troxell, M. L. 2010; 120 (2): 409-418

    Abstract

    Mutationally activated protein kinases are appealing therapeutic targets in breast carcinoma. Mutations in phosphatidylinositol-3-kinase (PI3KCA) have been described in 8-40% of invasive breast carcinomas, and AKT1 mutations have been characterized in 1-8% of breast carcinomas. However, there is little data on these mutations in breast precursor lesions. To further delineate the molecular evolution of breast tumorigenesis, samples of invasive breast carcinoma with an accompanying in situ component were macro dissected from formalin-fixed paraffin embedded tissue and screened for mutations in PIK3CA exons 7, 9, 20, and AKT1 exon 2. Laser capture micro dissection (LCM) was performed on mutation-positive carcinomas to directly compare the genotypes of separated invasive and in situ tumor cells. Among 81 cases of invasive carcinoma, there were eight mutations in PIK3CA exon 20 (7 H1047R, 1 H1047L) and four mutations in exon 9 (2 E545K, 1 E542K, 1 E545G), totaling 12/81 (14.8%). In 11 cases examined, paired LCM in situ tumor showed the identical PIK3CA mutation in invasive and in situ carcinoma. Likewise, 3 of 78 (3.8%) invasive carcinomas showed an AKT1 E17K mutation, and this mutation was identified in matching in situ carcinoma in both informative cases. Mutational status did not correlate with clinical parameters including hormone receptor status, grade, and lymph node status. The complete concordance of PIK3CA and AKT1 mutations in matched samples of invasive and in situ tumor indicates that these mutations occur early in breast cancer development and has implications with regard to therapeutics targeted to the PI3 kinase pathway.

    View details for DOI 10.1007/s10549-009-0406-1

    View details for Web of Science ID 000275633300014

    View details for PubMedID 19418217

  • High prevalence of PIK3CA/AKT pathway mutations in papillary neoplasms of the breast MODERN PATHOLOGY Troxell, M. L., Levine, J., Beadling, C., Warrick, A., Dunlap, J., Presnell, A., Patterson, J., Shukla, A., Olson, N. R., Heinrich, M. C., Corless, C. L. 2010; 23 (1): 27-37

    Abstract

    Papillary lesions of the breast have an uncertain relationship to the histogenesis of breast carcinoma, and are thus diagnostically and managerially challenging. Molecular genetic studies have provided evidence that ductal carcinoma in situ and even atypical ductal hyperplasia are precursors of invasive carcinoma. However, papillary lesions have been seldom studied. We screened papillary breast neoplasms for activating point mutations in PIK3CA, AKT1, and RAS protein-family members, which are common in invasive ductal carcinomas. DNA extracts were prepared from sections of 89 papillary lesions, including 61 benign papillomas (28 without significant hyperplasia; 33 with moderate to florid hyperplasia), 11 papillomas with atypical ductal hyperplasia, 7 papillomas with carcinoma in situ, and 10 papillary carcinomas. Extracts were screened for PIK3CA and AKT1 mutations using mass spectrometry; cases that were negative were further screened for mutations in AKT2, BRAF, CDK, EGFR, ERBB2, KRAS, NRAS, and HRAS. Mutations were confirmed by sequencing or HPLC assay. A total of 55 of 89 papillary neoplasms harbored mutations (62%), predominantly in AKT1 (E17K, 27 cases) and PIK3CA (exon 20 >exon 9, 27 cases). Papillomas had more mutations in AKT1 (54%) than in PIK3CA (21%), whereas papillomas with hyperplasia had more PIK3CA (42%) than AKT1 (15%) mutations, as did papillomas with atypical ductal hyperplasia (PIK3CA 45%, AKT1 27%, and NRAS 9%). Among seven papillomas with carcinoma in situ, three had AKT1 mutations. The 10 papillary carcinomas showed an overall lower frequency of mutations, including 1 with an AKT1 mutation (in a tumor arising from a papilloma), 1 with an NRAS gene mutation (Q61H), and 2 with PIK3CA mutations (1 overlapping with the NRAS Q61H). These findings indicate that approximately two-thirds of papillomas are driven by mutations in the PI3CA/AKT pathway. Some papillary carcinomas may arise from these lesions, but others may have different molecular origins.

    View details for DOI 10.1038/modpathol.2009.142

    View details for Web of Science ID 000273248500003

    View details for PubMedID 19898424

  • Rejection Versus Posttransplantation Lymphoproliferative Disorder in a Renal Transplant Recipient AMERICAN JOURNAL OF KIDNEY DISEASES Troxell, M. L., Dunlap, J. B., Mittalhenkle, A., Ishag, M., Fan, G., Huang, J. Z., Gatter, K., Byrd, D. M., Webster, D., Houghton, D. C. 2008; 52 (6): 1174-1179

    View details for DOI 10.1053/j.ajkd.2008.04.033

    View details for Web of Science ID 000261489800020

    View details for PubMedID 18706749

  • Renal pathology in hematopoietic cell transplantation recipients 96th Annual Meeting of the United-States-and-Canadian-Academy-of-Pathology Troxell, M. L., Pilapil, M., Miklos, D. B., Higgins, J. P., Kambham, N. NATURE PUBLISHING GROUP. 2008: 396–406

    Abstract

    Hematopoietic cell transplantation-associated renal injury may be related to a combination of factors including chemotherapy, radiation, infection, immunosuppressive agents, ischemia, and graft-versus-host disease. Renal biopsy specimens from hematopoietic cell transplant recipients at two institutions (Stanford University Medical Center and Oregon Health & Science University) were reviewed in correlation with clinical data. Fifteen cases were identified (post hematopoietic cell transplant time 0.7-14.5 years), including six with autologous hematopoietic cell transplant. Indications for renal biopsy included proteinuria (n=13; nephrotic range in 8), increased serum creatinine (n=10), or both (n=6). Many patients had multiple pathologic findings on renal biopsy. Membranous glomerulonephritis was the most common diagnosis (n=7), including two patients with autologous hematopoietic cell transplant and five with evidence of chronic graft-versus-host disease elsewhere. Four membranous glomerulonephritis patients achieved sustained remission with rituximab therapy. Other glomerular pathology included focal segmental glomerulosclerosis (n=1) and minimal change disease (n=1). Evidence of thrombotic microangiopathy was common (in isolation or combined with other pathology), as was acute tubular necrosis and tubulointerstitial nephritis. Of 14 patients with follow-up (2-64 months, mean 19 months), 6 had chronic renal insufficiency (serum creatinine >1.5 mg/dl), 2 had end stage renal disease, and 6 had essentially normal renal function. Our retrospective study shows that renal dysfunction in hematopoietic cell transplant recipients is often multifactorial, and biopsy may reveal treatable causes. Membranous glomerulonephritis is seen in autologous and allogeneic hematopoietic cell transplant recipients, and may respond to anti-B-cell therapy, which has implications regarding pathogenesis and relationship to graft-versus-host disease.

    View details for DOI 10.1038/modpathol.3801011

    View details for Web of Science ID 000254288500005

    View details for PubMedID 18223556

  • Immunohistochemical staining of papillary breast lesions APPLIED IMMUNOHISTOCHEMISTRY & MOLECULAR MORPHOLOGY Troxell, M. L., Masek, M., Sibley, R. K. 2007; 15 (2): 145-153

    Abstract

    The separation of ductal papilloma from intraductal papillary carcinoma of the breast on hematoxylin and eosin stained sections often presents diagnostic difficulty. Immunohistochemical staining is often employed in diagnosis, historically with smooth muscle actin (SMA). In this study, the staining characteristics of a panel of myoepithelial markers (calponin, p63, P-cadherin), were compared with SMA, and the epithelial expression of CD44s was assessed in 99 papillary lesions. SMA, calponin, and p63 demonstrated myoepithelial cells in 61%, 63%, and 65% of papillary lesions, respectively. However, specificity was quite variable. Calponin-stained stromal myofibroblasts (35% of cases), vessel pericytes (92%), and endothelial cells (69%), though each to a lesser degree than SMA. Calponin also showed cross reactivity with epithelium in 18% of cases. p63 was almost completely restricted to myoepithelial cell nuclei, and did not stain vascular smooth muscle or myofibroblasts. However, p63 stained the epithelial component in one papillary carcinoma, a basal layer of cells in 1 biphasic invasive carcinoma, and the cytoplasm in 1 case. P-cadherin stained both epithelial and myoepithelial cells. The epithelial expression of CD44s and did not distinguish papillomas from papillary carcinomas. Thus, P-cadherin and CD44s are not useful in the characterization of papillary lesions. Given increased specificity as compared with SMA, the combination of p63 and calponin is recommended for analysis of breast papillary lesions.

    View details for Web of Science ID 000246870200005

    View details for PubMedID 17525625

  • Evaluation of Her-2/neu status in carcinomas with amplified chromosome 17 centromere locus AMERICAN JOURNAL OF CLINICAL PATHOLOGY Troxell, M. L., Bangs, C. D., Lawce, H. J., Galperin, I. B., Baiyee, D., West, R. B., Olson, S. B., Cherry, A. M. 2006; 126 (5): 709-716

    Abstract

    Accurate assessment of Her-2/neu (erb-b2) status in breast carcinoma is essential for therapy planning. Clinical assays are targeted at protein overexpression (immunohistochemical analysis) or gene amplification (fluorescence in situ hybridization [FISH]). Cases with aberrant FISH signal patterns are problematic and may lead to underreporting of Her-2/neu amplification. We performed FISH with additional chromosome 17 probes, SMS (Smith-Magenis syndrome critical region) and RARA (retinoic acid receptor), on 7 cases with unusual Her-2/CEP17 (chromosome 17 centromere control probe) results to assess whether different measurements of chromosome 17 copy number might clarify the Her-2/neu amplicon status. Although the Her-2/CEP17 ratio scores were within normal range (<2.0), the Her-2/SMS or Her-2/RARA ratio revealed amplification of Her-2/neu in 5 of 7 cases. Immunohistochemical analysis demonstrated Her-2/neu protein overexpression in the same 5 cases only. We describe novel application of SMS/RARA FISH probes for assessing cases with complex Her-2/CEP17 FISH patterns. Such additional data, correlated with immunohistochemical analysis, may help guide therapy in patients with breast carcinoma.

    View details for DOI 10.1309/9EYM6VE58F2YCD9F

    View details for Web of Science ID 000241420000007

    View details for PubMedID 17050068

  • Evaluation of C4d staining in liver and small intestine allografts 93rd Annual Meeting of the United-States-and-Canadian-Academy-of-Pathology Troxell, M. L., Higgins, J. P., Kambham, N. COLLEGE AMER PATHOLOGISTS. 2006: 1489–96

    Abstract

    Antibody-mediated humoral rejection in kidney and heart allografts is well recognized and is often associated with poor outcome. C4d deposition in allograft biopsy specimens occurs at sites of antibody-mediated complement activation and has become one of the histopathologic criteria for diagnosis of humoral rejection in the kidney and the heart.To study immunohistochemical C4d staining as a potential diagnostic marker in liver and small intestine allograft biopsy specimens.Thirty-six small intestine and 71 liver specimens, including native specimens, allografts with and without histologic features of acute cellular rejection, and explants, were stained with antisera to C4d using an immunohistochemical method on formalin-fixed, paraffin-embedded tissue.In small intestine, C4d labeled capillaries in 27% of cases with no evidence of rejection, 36% of cases with evidence of acute rejection, and 2 (28%) of 7 specimens of native normal small intestine. In liver allograft biopsy specimens, C4d stained endothelium of veins, arteries, and/or sinusoids in 2 (8%) of 25 cases of acute rejection with central vein involvement; C4d staining was negative in biopsy specimens with no evidence of rejection. C4d stained the endothelium in a subset of explanted liver allografts with ductopenic rejection or chronic vascular rejection and strongly stained 1 explant with features of hyperacute rejection.The clinical utility of C4d staining in solid organ transplantation may vary by organ. Our data show C4d is unlikely to have utility in small intestine allograft biopsy specimens; however, further study in liver allografts, in conjunction with donor-specific antibody testing, is warranted.

    View details for Web of Science ID 000241049200013

    View details for PubMedID 17090190

  • Comparison of C4d immunostaining methods in renal allograft biopsies 8th Banff Conference on Allograft Pathology Troxell, M. L., Weintraub, L. A., Higgins, J. P., Kambham, N. AMER SOC NEPHROLOGY. 2006: 583–91

    Abstract

    Immunostaining of renal allograft biopsies for C4d deposition has become an important diagnostic tool in the recognition of humoral-mediated graft rejection. The majority of studies have been performed on frozen tissue sections with one of several commercially available antibody reagents. However, only a single small series that compared reagents or methods, including staining of formalin-fixed, paraffin-embedded tissue, has been published. Two different staining methods in 138 renal allograft biopsies were compared directly: A mAb (Quidel, San Diego, CA) on frozen tissue sections with indirect immunofluorescence (IF) and a polyclonal antibody (Biomedica Gruppe, distributed by ALPCO, Windham, NH) applied to formalin-fixed, paraffin-embedded tissue with immunohistochemical (IHC) detection. An initial data set of 107 consecutive cases showed complete agreement between staining methods in 104 (97%) cases. Overall, nine of 107 cases were positive with one or both methods, representing 8.4% of all allograft biopsies tested, 15% of clinically indicated biopsies, and 24% of biopsies with a histologic diagnosis of acute cellular rejection. A second set of 31 cases included 17 cases that were positive by either method, with concordance in 29 of 31 cases. Combining the two data sets, the overall specificity of the IHC method compared with IF was 98%, and sensitivity was 87.5%. Direct comparison demonstrates that IHC staining of formalin-fixed, paraffin-embedded tissue with anti-C4d polyclonal antibody has acceptable sensitivity and specificity, as compared with IF staining of frozen tissue with the Quidel mAb.

    View details for Web of Science ID 000242172900035

    View details for PubMedID 17699262

  • Glomerular and tubular basement membrane calcinosis: Case report and literature review AMERICAN JOURNAL OF KIDNEY DISEASES Troxell, M. L., Higgins, J. P., Sibley, R. K. 2006; 47 (2)

    Abstract

    Nephrocalcinosis most commonly manifests as renal calculi or deposition within the tubulointerstitial compartment. Conversely, calcium deposition within glomeruli is extremely rare. We present the case of a 50-year-old man with multiple medical problems, including hepatitis C, diabetes, hypertension, proteinuria, and chronic renal failure. Renal biopsy showed impressive calcium deposits along glomerular basement membranes and tubular basement membranes, within intracellular organelles, and in the interstitium in the setting of a normal serum calcium level. Seven months after biopsy, the patient is on hemodialysis therapy. Although serological and medical examination failed to show a treatable cause for this patient's glomerular calcinosis, individual case reports in the literature have described resolution of calcinosis-associated nephrotic syndrome with treatment of the primary cause of hypercalcemia.

    View details for DOI 10.1053/j.ajkd.2005.10.030

    View details for Web of Science ID 000235189300026

    View details for PubMedID 16431246

  • Renal juxtaglomerular apparatus hyperplasia NEPHROLOGY DIALYSIS TRANSPLANTATION Troxell, M. L., Scandling, J. D., Sibley, R. K. 2005; 20 (10): 2282-2283

    View details for DOI 10.1093/ndt/gfh883

    View details for Web of Science ID 000232102800045

    View details for PubMedID 15941848

  • Renal tubular injury associated with anagrelide NEPHROLOGY DIALYSIS TRANSPLANTATION Rodwell, G. E., Troxell, M. L., Lafayette, R. A. 2005; 20 (5): 988-990

    View details for DOI 10.1093/ndt/gfh726

    View details for Web of Science ID 000229083800022

    View details for PubMedID 15728271

  • Mutant cadherin affects epithelial morphogenesis and invasion, but not transformation JOURNAL OF CELL SCIENCE Troxell, M. L., Loftus, D. J., NELSON, W. J., MARRS, J. A. 2001; 114 (6): 1237-1246

    Abstract

    MDCK cells were engineered to reversibly express mutant E-cadherin protein with a large extracellular deletion. Mutant cadherin overexpression reduced the expression of endogenous E- and K-cadherins in MDCK cells to negligible levels, resulting in decreased cell adhesion. Despite severe impairment of the cadherin adhesion system, cells overexpressing mutant E-cadherin formed fluid-filled cysts in collagen gel cultures and responded to hepatocyte growth factor/scatter factor (HGF/SF) that induced cellular extension formation with a frequency similar to that of control cysts. However, cells were shed from cyst walls into the lumen and into the collagen matrix prior to and during HGF/SF induced tubule extension. Despite the propensity for cell dissociation, MDCK cells lacking cadherin adhesion molecules were not capable of anchorage-independent growth in soft agar and cell proliferation rate was not affected. Thus, cadherin loss does not induce transformation, despite inducing an invasive phenotype, a later stage of tumor progression. These experiments are especially relevant to tumor progression in cells with altered E-cadherin expression, particularly tumor samples with identified E-cadherin extracellular domain genomic mutations.

    View details for Web of Science ID 000167952200022

    View details for PubMedID 11228167

  • Inhibiting cadherin function by dominant mutant E-cadherin expression increases the extent of tight junction assembly JOURNAL OF CELL SCIENCE Troxell, M. L., Gopalakrishnan, S., McCormack, J., Poteat, B. A., Pennington, J., Garringer, S. M., Schneeberger, E. E., NELSON, W. J., Marrs, J. A. 2000; 113 (6): 985-996

    Abstract

    Previous studies have shown that induction of cadherin-mediated cell-cell adhesion leads to tight junction formation, and that blocking cadherin-mediated cell-cell adhesion inhibits tight junction assembly. Here we report analysis of tight junction assembly in MDCK cells overexpressing a mutant E-cadherin protein that lacks an adhesive extracellular domain (T151 cells). Mutant E-cadherin overexpression caused a dramatic reduction in endogenous cadherin levels. Despite this, tight junction assembly was extensive. The number of tight junction strands observed by freeze-fracture electron microscopy significantly increased in T151 cells compared to that in control cells. Our data indicate that the hierarchical regulation of junctional complex assembly is not absolute, and that inhibition of cadherin function has both positive and negative effects on tight junction assembly.

    View details for Web of Science ID 000086312400010

    View details for PubMedID 10683147

  • Cadherin function in junctional complex rearrangement and posttranslational control of cadherin expression AMERICAN JOURNAL OF PHYSIOLOGY-CELL PHYSIOLOGY Troxell, M. L., Chen, Y. T., Cobb, N., NELSON, W. J., MARRS, J. A. 1999; 276 (2): C404-C418

    Abstract

    The role of E-cadherin, a calcium-dependent adhesion protein, in organizing and maintaining epithelial junctions was examined in detail by expressing a fusion protein (GP2-Cad1) composed of the extracellular domain of a nonadherent glycoprotein (GP2) and the transmembrane and cytoplasmic domains of E-cadherin. All studies shown were also replicated using an analogous cell line that expresses a mutant cadherin construct (T151) under the control of tet repressor. Mutant cadherin was expressed at approximately 10% of the endogenous E-cadherin level and had no apparent effect on tight junction function or on distributions of adherens junction, tight junction, or desmosomal marker proteins in established Madin-Darby canine kidney cell monolayers. However, GP2-Cad1 accelerated the disassembly of epithelial junctional complexes and delayed their reassembly in calcium switch experiments. Inducing expression of GP2-Cad1 to levels approximately threefold greater than endogenous E-cadherin expression levels in control cells resulted in a decrease in endogenous E-cadherin levels. This was due in part to increased protein turnover, indicating a cellular mechanism for sensing and controlling E-cadherin levels. Cadherin association with catenins is necessary for strong cadherin-mediated cell-cell adhesion. In cells expressing low levels of GP2-Cad1, protein levels and stoichiometry of the endogenous cadherin-catenin complex were unaffected. Thus effects of GP2-Cad1 on epithelial junctional complex assembly and stability were not due to competition with endogenous E-cadherin for catenin binding. Rather, we suggest that GP2-Cad1 interferes with the packing of endogenous cadherin-catenin complexes into higher-order structures in junctional complexes that results in junction destabilization.

    View details for Web of Science ID 000078595500015

    View details for PubMedID 9950768