They derive from the somatostatin-producing delta cells of the pancreas or the endocrine cells of the digestive tract and may be sporadic (93.1%) or familial (6.9%) in association with NF1, multiple endocrine neoplasia type 1 (MEN 1), and Von Hippel-Lindau syndrome [6]. This evidence concerns the gene SST and neurofibromatosis type 1.