These mutations can occur in genetic syndromes, such as multiple endocrine neoplasia type 1 (MEN1), tuberous sclerosis complex (TSC1/2), neurofibromatosis type 1 (NF1), and von Hippel–Lindau (VHL) syndrome, or in sporadic NENs, and can be germline or somatic mutations [15,16,17]. The gene discussed is NF1; the disease is von Hippel-Lindau disease.