Most patients have no family history, i.e. they are not hereditary, but in a minority of patients islet cell tumours are one manifestation of certain endocrine tumour syndromes, which are prone to multiple tumours and are often combined with tumours of other endocrine glands or other systems, and have a familial predisposition. These syndromes include multiple endocrine adenomatosis type 1 (MEN1), VHL syndrome, and neurofibromatosis type 1.