FMTC is considered today as a clinical variant of MEN2A, and it can be diagnosed based on a set of specific criteria: more than 10 family members with MTC, multiple carriers or affected members over 50 years of age, and a sufficient medical history to exclude the presence of PHEO and PHPT, or the presence of at least four family members with MTC but without other manifestations of MEN2A [40,113,114]. The gene discussed is RET; the disease is familial medullary thyroid carcinoma.