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. Here, RET is linked to tumor of parathyroid gland.