MEN2 comprises MEN2A, which features familial MTC (FMTC) [12] or MTC plus pheochromocytoma and hyper-parathyroidism/parathyroid adenoma, and MEN2B also characterized by MTC and pheochromocytoma, but with mucosal ganglioneuromas and marfanoid habitus. This evidence concerns the gene RET and familial medullary thyroid carcinoma.