RET and medullary thyroid gland carcinoma: In MEN3, which was previously referred to as MEN2B, MTC and pheochromocytoma occur in association with a marfanoid habitus, mucosal neuromas, medullated corneal fibers, and intestinal autonomic ganglion dysfunction leading to megacolon (Thakker, 1998), with rare occurrence of parathyroid tumors.