Multiple Endocrine Neoplasia Type 2 (MEN-2): An Update. Multiple endocrine neoplasia type 2 (MEN-2) is an autosomal dominant hereditary cancer syndrome. The disorder is caused by missense mutations of the RET proto-oncogene that result in their gain of function. Three distinct clinical subtypes of MEN-2 are characterized: MEN-2A, MEN-2B, and familial MTC (FMTC). The precise RET mutations may su...