Multiple endocrine neoplasia type 2: an overview.

Multiple endocrine neoplasia type 2 is historically composed of three clinical subtypes, all of which are associated with germline mutations in the RET proto-oncogene. Multiple endocrine neoplasia type 2A, familial medullary thyroid carcinoma, and multiple endocrine neoplasia type 2B are collectively associated with a 70-100% risk of medullary thyroid carcinoma by age 70 years. Pheochromocytomas are identified in 50% of individuals with multiple endocrine neoplasia type 2A and multiple endocrine neoplasia type 2B. Furthermore, those with multiple endocrine neoplasia type 2A have a 20-30% risk for primary hyperparathyroidism. Individuals with multiple endocrine neoplasia type 2B often have distinct physical features including mucosal neuromas of the lips and tongue, medullated corneal nerve fibers, ganglioneuromatosis of the gastrointestinal tract, distinctive facies with enlarged lips, and a "Marfanoid" body habitus. Clinical recognition and accurate diagnosis of individuals and families who are at risk of harboring a germline RET mutation is critical for the prevention and management of potentially life-threatening neoplasms. This overview summarizes the clinical description of multiple endocrine neoplasia type 2, diagnosis and testing strategies, management and surveillance, and differential diagnosis for other related syndromes.