Disruption of function by germline mutations in RET have been associated with several diseases in humans including three related inherited cancers: multiple endocrine neoplasia type IIA (MEN2A), multiple endocrine neoplasia type IIB (MEN2B), and familial medullary thyroid carcinoma (FMTC). The gene discussed is RET; the disease is multiple endocrine neoplasia type 2B.