The vast majority (90 %) of PanNETs occur sporadically, but some occur in the setting of associated familial syndromes including multiple endocrine neoplasia type 1 (MEN1), von Hippel-Lindau syndrome (VHL), neurofibromatosis type 1 (NF1), tuberous sclerosis complex (TSC) and the recently discovered glucagon cell adenomatosis (GCA) [5, 79]. This evidence concerns the gene MEN1 and multiple endocrine neoplasia type 1.