NF1 and multiple endocrine neoplasia type 1: The majority of PNETs are sporadic, but some are associated with genetic syndromes, such as multiple endocrine neoplasia type 1 (MEN-1), von Hippel-Lindau (VHL) disease, neurofibromatosis type 1 (NF-1), and tuberous sclerosis (TS) [17].