MEN1 and gastrin-producing neuroendocrine tumor: MEN1 is defined clinically by the occurrence of multiple epithelial neuroendocrine tumors (eNETs), such as parathyroid adenoma/hyperplasia (up to 100%), pancreaticoduodenal eNETs (30–90%), pituitary adenoma (30–40%), bronchopulmonary tract eNETs (3–10%), and tumors of the gastrointestinal tract such as gastrinoma (50–80%), as well as non-eNETs, such as adrenocortical adenoma/carcinoma (20–40%) and breast carcinoma (7%) (2–5).