MEN1 and multiple endocrine neoplasia type 1: Cystic PNETs can be sporadic or associated with multiple endocrine neoplasia type 1 (MEN-1), an autosomal-dominant disorder caused by mutations in the tumor suppressor gene MEN1, characterized by the combined occurrence of tumors of the parathyroid glands, pancreatic islet cells, and the anterior pituitary gland [49,52,53,54,55].