Inclusion Criteria:

All Patients

   - Previously confirmed (histologically or cytologically) pediatric solid tumor (e.g.,
   neuroblastoma, sarcoma), lymphoma (including Hodgkin's lymphoma), or malignant brain
   tumors that are clinically or radiographically suspected to be relapsed, refractory,
   or recurrent for which there are no standard treatment options with curative
   potential. Note: patients with diffuse intrinsic pontine glioma (DIPG) may enroll
   without histological or cytological confirmation.

   - ≥ 2 years of age and ≤ 25 years of age at time of consent/assent

   - If ≥ age 16 years, Karnofsky performance status of ≥ 60. If < age 16 years, Lansky
   performance status ≥ 60

   - Platelets ≥ 75,000/µL (last transfusion, if any, must be at least 1 week prior to
   study registration, and, unless deemed medically necessary, no transfusions are
   allowed between registration and dosing)

   - Absolute neutrophil count ≥ 750/µL

   - Hemoglobin ≥ 8 g/dL (last transfusion must be at least 1 week prior to study
   registration, and, unless deemed medically necessary, no transfusions are allowed
   between registration and dosing)

   - Using the bedside Schwartz formula, estimated GFR (creatinine clearance) > 60
   ml/min/1.73m2

   - Alanine aminotransferase < 3 × ULN

   - Bilirubin < 2 × ULN

   - Patients who have undergone autologous or allogeneic bone marrow transplant must be at
   least 3 months from transplant.

   - Patients enrolling at total dose levels > 30 millicurie (mCi)/m2 must have
   availability or ability to collect an autologous hematopoietic stem cell back-up
   product prior to CLR 131 administration. At minimum, 2 x 10^6/kg cryopreserved CD34+
   cells must be available.

   - Patient or his or her legal representative is judged by the Investigator to have the
   initiative and means to be compliant with the protocol.

Patients with Pediatric Solid Tumor or Lymphoma

   - At least 1 measurable lesion with longest diameter of at least 10 mm. Patients with a
   lesion(s) that are determined to be Metaiodobenzylguanidine (MIBG) or positron
   emission tomography (PET) positive may be enrolled at the investigator's discretion,
   even if not associated with a measurable lesion of at least 10 mm. Patients with
   neuroblastoma who have detectable disease may enroll provided they meet the
   requirements of the International Neuroblastoma Response Criteria.

   - Patients with known brain metastases must have completed any radiotherapy or systemic
   treatments for brain metastases prior to enrollment; by investigator assessment be
   considered stable with no new signs or symptoms for at least 1 month, and on a stable
   dose of steroids (unchanged for three weeks prior to registration or on a steroid
   tapering regimen).

Patients with Recurrent or Refractory Brain Tumors

   - At least 1 measurable lesion with longest diameter of at least 10 mm on any imaging
   sequence.

   - Patients with previously known neurological deficits must be clinically stable at time
   of enrollment and able to complete all study related procedures. Patients with
   documented or newly diagnosed neurological deficits will be enrolled at the
   investigator's discretion.

   - If patient receives steroids for neurological symptom control, the dose must be stable
   (unchanged for three weeks prior to registration) or on a steroid tapering regimen.
   Initiation of steroids per routine care immediately prior to CLR 131 dosing is
   acceptable.

Exclusion Criteria:

   - Patients receiving active treatment for central nervous system metastases or those
   that are likely to require active treatment during anticipated participation in this
   trial. Patients with stable brain metastases treated with steroids may enroll at the
   investigator's discretion

   - For solid tumor and lymphoma patients only, central nervous system involvement unless
   previously treated with surgery, systemic therapy, or radiotherapy with the patient
   neurologically stable. Patients with metastatic brain tumors that have been previously
   treated are allowed, provided the patient is neurologically stable (determined at the
   investigator's discretion).

   - Antitumor therapy or investigational therapy, within 2 weeks of dosing. For certain
   types of radiation (craniospinal, total abdominal, whole lung [spot irradiation to
   skull-based metastases is not considered craniospinal radiation for the purposes of
   this study]), at least 3 months must have elapsed. No washout is required for
   palliative focal radiation. NOTE: Patients participating in non-interventional
   clinical trials (i.e., non-drug) are allowed to participate in this trial

   - Patients previously treated with iodine-131 (131I)-MIBG who have already received a
   cumulative I-131 dose > 54 mCi/kg or who would exceed 54 mCi/kg by participating in
   this trial, are not eligible.