Medullary thyroid cancer arises from parafollicular cells. Germline RET oncogene mutations occur with familial medullary thyroid cancer and multiple endocrine neoplasia (MEN) 2A and 2B. MEN should be ruled out with genetic testing prior to surgery, given its association with pheochromocytoma. Medullary thyroid cancer is treated with total thyroidectomy and central neck lymph node dissection. Levothyroxine is indicated to treat postoperative hypothyroidism in patients with medullary thyroid cancer with a goal serum TSH level within the reference range. Serum calcitonin, serum carcinoembryonic antigen levels, and neck ultrasound are part of routine cancer surveillance.
Approximately 25% of medullary thyroid cancers are hereditary; all patients with medullary thyroid cancer should be screened with RET proto-oncogene sequencing. Medullary thyroid cancer may be associated with several syndromes, including multiple endocrine neoplasia type 2A (MEN2A) (which may include pheochromocytoma and hyperparathyroidism), MEN2B (marfanoid habitus and mucosal ganglioneuromas), or familial medullary thyroid cancer (medullary thyroid cancer alone).