75% of MTCs are sporadic and the remaining 15% are hereditary as part of the Multiple Endocrine Neoplasia (MEN) type 2 syndrome and the familial MTC (FMTC).4,5 The MEN syndrome arises from a germline mutation in the REarranged during Transfection (RET) oncogene. Here, RET is linked to familial medullary thyroid carcinoma.