Adenoid Cystic Carcinoma
Adenoid cystic carcinoma (ACC) is a rare cancer that develops from the salivary glands. These can develop from the major salivary glands of the head and neck (the two parotid glands, which are located in front of the ears, the two submandibular glands, which are located just under the lower jaw, and the two sublingual glands, which are located under the tongue), the lacrimal glands (two glands that make tears located on the outside edges of the eyebrows), or the minor salivary glands (hundreds of tiny glands located throughout the lining of the nose, mouth, and throat). They are well-known to travel along nerve fibers in the salivary glands, in which they can spread to the base of the skull or brain. They are typically treated with surgery followed by post-operative radiation therapy. Although they are slow-growing, they can return several years later even after optimal treatment, either in the location that they began or in distant sites, such as the lung or bone.
ACCs are typically slow growing cancers that can be present for several years with mild symptoms before diagnosis. They typically affect younger patients, in which cancer is often not at the top of the list when these mild symptoms are brought to the attention of a physician. The symptoms depend on the location of the tumor. ACCs affecting the major salivary glands often present with a lump in that area, which is often slow-growing. ACCs affecting the minor salivary glands (in the mouth, nose, and throat) can present with nosebleeds, difficulty swallowing, or the feeling of congestion or a lump in the throat. If ACCs travel along large nerves before they are diagnosed, they can cause nerve dysfunction, such as facial weakness, numbness or tingling, visual changes, difficulty moving the tongue, or difficulty moving the eyes (depending on the nerves involved).
With ACC, the goal is to diagnose them before they are so advanced that they have spread. Typically, patients who have symptoms as noted above should be evaluated with an MRI (magnetic resonance imaging) scan of the head and neck. These scans help to determine the extent of the lesion itself and whether it has traveled along nerves to the base of the skull. In addition, there should be an evaluation of the chest with a CT (computed tomography) scan or chest x-ray to ensure that the tumor has not spread. The diagnosis is truly made when a piece of tissue is sampled from the mass or lesion and reviewed; a biopsy is required to confirm the pathology as adenoid cystic carcinoma.
For patients with localized ACCs, the primary treatment is surgical resection. The goal is to remove the tumor with a rim of normal tissue around it. However, these tumors are locally infiltrative and are known to travel along nerves, so radiation therapy is warranted regardless of the status of the margin (edges of the resection). Typically, radiation therapy starts approximately 4-6 weeks after surgery and lasts approximately 6 weeks (of daily treatments, Monday-Friday). ACCs are rare cancers, so both surgery and radiation at a high-volume academic center by highly specialized head and neck and skull base surgeons and radiation oncologists is important for the best outcomes. If surgery is impossible (due to location or extent of the primary tumor), then a radiation-based approach can be used (but is not as effective). If the tumor has spread to other areas (at presentation or later), systemic therapies are used. There are ongoing research efforts to determine systemic treatments (chemotherapy, biological therapies, and immunologic therapies) to try to eliminate the disease at all areas. This is an area of active research.