Germline mutations in RET, seen in 98% of patients with hereditary MTC [6], are associated with several clinical conditions including familial MTC (FMTC) [7–10] multiple endocrine neoplasia (MEN) type 2A [11–13], and MEN2B [11, 12, 14]. The gene discussed is RET; the disease is multiple endocrine neoplasia type 2A.