Figure 1.

The clinical manifestations and estimated tumor penetrance of multiple endocrine neoplasia type 1 (MEN1) syndrome. The main manifestations of MEN1 include anterior pituitary adenomas, pancreatic neuroendocrine tumors, and primary hyperparathyroidism. Except for multi-gland hyperparathyroidism which approximates 95% penetrance by age 50, the manifestations of other tumors in MEN1 have no genotype-phenotype correlation and cannot be predicted, even within kindreds. Neuroendocrine tumor (NET) hormone secretion in the anterior pituitary and pancreas can be considered functional or non-functional, while duodenal NET and parathyroid adenomas are always functional with the secretion of gastrin and parathyroid hormone, respectively. As pictured, Zollinger-Ellison Syndrome can present with multiple submucosal duodenal gastrinomas with simultaneous pancreatic gastrinomas, non-functional pancreatic tumors, as well as the development of gastric NET typically within thickened gastric folds (not pictured). Less frequent manifestations of MEN1 include foregut bronchopulmonary and thymic neuroendocrine tumors, as well as adrenal cortical adenomas and pheochromocytomas. Skin manifestations of MEN1 include lipomas that can occur anywhere on the body, collagenomas mostly on the trunk, and facial angiofibromas on the nasal bridge and cheeks. Manifestations that have been described but are not pictured include meningiomas, leiomyoma (uterus, esophagus, ureter, bladder), café-au-lait spots, and malignant breast tumors.