Epidemiology, clinical features and diagnosis of gastroenteropancreatic endocrine tumours

Gastroenteropancreatic (GEP) neoplasms originate from any of the various ce ll types belonging to the neuroendocrine system. A general characteristic o f GEP endocrine tumours is that the vast majority produce and secrete a mul titude of peptide hormones and amines. Many patients with malignant metasta sising tumours present clinical symptoms related to hormone hyperproduction . These include the so-called carcinoid syndrome, characterised by flushing , diarrhoea, wheezing and right heart disease, which is predominantly assoc iated with the serotonin- and tachykinins-producing carcinoids of the midgu t. Several types of syndrome associated with GEP endocrine tumors are cause d by overproduction of a specific hormone. For instance, the well-known Zol linger-Ellison syndrome is gastrin-mediated. The so-called 'insulinoma synd rome' depends on excessive production of insulin and proinsulin, resulting in hypoglycemia. The 'glucagonoma syndrome' is characterised by necrolytic migratory erythema, diabetes and diarrhoea. The Verner-Morrison syndrome, w hich is brought about by high circulating levels of vasointestinal peptide (VIP), produces severe secretory diarrhoea. Finally the 'somatostatinoma sy ndrome' involves gallbladder dysfunction and gallstones, diarrhoea with or without steatorrhea, and impaired glucose tolerance. The biochemical diagnosis of endocrine digestive tumors is based on general and specific markers. The best general markers are chromogranin A (CgA) an d pancreatic polypeptide (PP). Specific markers for endocrine tumors includ e insulin, gastrin, glucagon, vaso intestinal polypeptide (VIP), somatostat in and the primary cathabolic product of serotonin, 5-hydroxyndoleacetic ac id (5-HIAA). Localisation procedures commonly applied, in the diagnosis of endocrine tumours include ultrasound (US), computed tomography (CT) and som atostatin receptor scintigraphy (SRS).