Somatic MEN1 mutations are observed in 30% of the common sporadic counterparts (e.g., parathyroid adenoma, gastrinoma, insulinoma and bronchial carcinoid) of the endocrine tumor types seen in familial MEN1, except in sporadic pituitary tumors (only 1–5% with MEN1 mutation) [28]. Here, MEN1 is linked to gastrin-producing neuroendocrine tumor.