Abstract
Medullary thyroid carcinoma, a tumor of the thyroid parafollicular cells (C cells) that secrete calcitonin, constitutes about 10 percent of all thyroid cancers, being considerably less common than papillary or follicular thyroid carcinoma. It occurs as both a sporadic and a familial disease. Among families, it occurs alone or as a component of either multiple endocrine neoplasia type 2A (MEN-2A), comprising medullary thyroid carcinoma, pheochromocytoma, and hyperparathyroidism, or the rarer MEN-2B, comprising medullary thyroid carcinoma, pheochromocytoma, and mucosal neuromas. Medullary thyroid carcinoma was among the first cancers whose genetic features were exploited for prevention. This was achieved by recognizing that . . .