Multiple endocrine neoplasia type 2

Multiple endocrine neoplasia type 2 (MEN 2) is a rare cancer susceptibility syndrome which has at least three distinct variants: MEN 2A, MEN 2B, and familial medullary thyroid carcinoma (FMTC). The syndrome was first described by John Sipple in 1961 (1). The features of MEN 2A and its clinical variants are outlined in Box 6.12.1. Medullary thyroid carcinoma (MTC) is seen in all variants of MEN 2A and is frequently the earliest neoplastic manifestation, reflecting its earlier and overall higher penetrance. MEN 2 is due to the autosomal dominant inheritance of a germline missense mutation in the ‘hot-spot’ regions of the rearranged during transfection (RET) (OMIM 164761) proto-oncogene (2, 3). MEN 2 has an estimated prevalence of 1:30 000, with MEN 2A accounting for more than 75% of cases. The introduction of RET screening in family members of affected individuals has significantly altered the clinical outcome of MEN 2, by allowing prophylactic surgery for MTC, and screening enabling early intervention for phaeochromocytoma (4, 5). Prior to the availability of genetic screening, more that half of MEN 2 affected individuals died before or during the fifth decade from metastatic MTC or cardiovascular complications from an underlying phaeochromocytoma.