Medullary Thyroid cancer(MTC) is considered with other well differentiated thyroid cancers, but is different in that the cells of origin are the para-follicular cells. These are cells in the thyroid gland that are not involved in making thyroid hormone. Para-follicular cells make a hormone called calcitonin. It may play a role in calcium regulation. The importance of calcitonin in humans is unknown. MTC accounts for about 5% of thyroid cancer. Generally it occurs equally between men and women.
There are two forms of MTC, hereditary and sporadic. About 25% of MTC is inherited, usually as a part of a Multiple Endocrine Neoplastic syndrome( MEN 2). When MTC is diagnosed the patient should be evaluated for an inherited syndrome. Specifically, we need to be sure the patient does not have an associated pheochromocytoma. If that evaluation is negative then MTC is considered to be sporadic. Sporadic MTC usually presents as a solitary nodule while the inherited form is multi-centric and typically present at a much younger age.
MTC is treated with a total thyroidectomy with an aggressive central (level 6) lymph node dissection. Metastatic disease is more common with MTC and its prognosis is worse than other well differentiated thyroid cancers. The patient’s preoperative calcitonin level may suggest the risk of metastatic disease. Levels less than 40 are associated with a significanty lower risk of lymph node metastasis. calcitonin levels greater than 150 should probably have a preoperative work up for distant metastasis. MTC doesn’t absorb iodine, therefore RAI isn’t useful. Unfortunately, traditional chemotherapy and radiation therapy have little to offer. However, some promising post-surgical therapies for MTC are under development. Recently, Vandetanib has been shown to be effective in treating metastatic medullary thyroid cancer