Medullary thyroid carcinoma and multiple endocrine neoplasia type 2.

Medullary thyroid carcinoma (MTC) occurs as both a sporadic and an inherited disease. MTC is a consistent feature of multiple endocrine neoplasia (MEN) 2A, MEN 2B, and familial non-MEN MTC (FMTC). Plasma calcitonin is a sensitive and specific marker for the presence of MTC. Genetic testing can identify mutant gene carriers, and prophylactic total thyroidectomy should be carried out in patients with the mutant gene. The outcome of MTC is progressively worse in FMTC, MEN 2A, sporadic MTC, and MEN 2B, and MEN 2B has been found to have the worst prognosis. There is a significant genotype-phenotype correlation, which allows a more sensitive individualized approach to the timing and extent of prophylactic thyroidectomy.