Medullary Thyroid Cancer

Medullary thyroid cancer (MTC) is a tumor of the calcitonin-producing parafollicular C-cells in the thyroid. 25% of MTC is hereditary and associated with multiple endocrine neoplasia (MEN) 2A or 2B, which is characterized by germline mutations in the RET proto-oncogene; the remaining 75% are sporadic in nature. Most patients with sporadic MTC present with a solitary thyroid nodule or cervical lymphadenopathy. Patients with hereditary MTC often have bilateral disease. Approximately 75% of patients will have metastatic disease at the time of presentation. MTC is diagnosed by neck ultrasound and fine needle aspiration biopsy. Serum calcitonin and carcinoembryonic antigen serve as tumor markers and levels often correlate with disease burden. All patients additionally must undergo genetic testing to determine if they have MEN, as patients with MEN require testing and treatment for pheochromocytoma prior to resection of MTC. Treatment for MTC contained to the thyroid is total thyroidectomy with bilateral central neck lymph node dissection; lateral neck lymph node dissection is performed if there is evidence of lymphatic spread. Surgery is the only potentially curative treatment for MTC; systemic therapies are often of limited efficacy. Post-operative surveillance is performed with serial exam, neck ultrasound, and calcitonin and CEA levels. Prognosis is dependent on stage at initial presentation, with patients who present with stage I or II disease having greater than 90% 10-year survival.