MEN1 and neurofibromatosis type 1: Up to 10% of NENs can occur in the context of hereditary syndromes, such as multiple endocrine neoplasia type 1 (MEN1), multiple endocrine neoplasia type 2 (MEN2), multiple endocrine neoplasia type 4 (MEN4), Von Hippel–Lindau (VHL), neurofibromatosis type 1 (NF1), and tuberous sclerosis [58], the most frequent localization being the pancreas [58, 59].