The majority of GEP-NENs (>95%) occurs in sporadic forms, while 5% of cases are part of a polydistrict syndrome, such as multiple endocrine neoplasm type 1 (MEN1), neurofibromatosis type 1 (NF1), and von Hippel–Lindau syndrome (VHL) [6,7]. This evidence concerns the gene MEN1 and von Hippel-Lindau disease.