ABSTRACT
Gastrointestinal neuroendocrine tumours which give rise to clinical diagnosis in life are all rare, the overall prevalence being approximately 10 in 1 000 000 of population. Neuroendocrine tumours that have been silent in life are far more common (see ‘Carcinoid tumours’ below). For many subtypes, the pancreas is the most common site of the primary (e.g. insulinoma, gastrinoma, vipoma), with the proximal small bowel accounting for most of the rest. Carcinoid tumours are an exception, with most tumours arising in the appendix/distal small bowel. Neuroendocrine tumours are either sporadic or arise in a familial form, associated with the MEN type 1 syndrome (the latter particularly the case when there are multiple neuroendocrine tumours).
