Somatostatinoma

Somatostatinoma (SSoma) is an extremely rare pancreatic neuroendocrine tumor or duodenal endocrine tumor (see these terms) that originates either in the pancreas (50%) or the gastrointestinal tract (50%) and mainly presents with non-specific symptoms of abdominal pain, weight loss, jaundice and diarrhea but, in approximately 20% of pancreatic cases, leads to a somatostatin hypersecretion syndrome (somatostatinoma syndrome) characterized by diabetes mellitus, cholelithiasis, steatorrhea and hypochlorhydria.

Epidemiology

The estimated incidence is of 1/40,000,000. Approximately 80 cases of pancreatic SSoma have been reported to date but this is probably an underestimate.

Clinical description

SSomas usually range in size from 3-11cm. Most SSomas present with non-specific symptoms of abdominal pain, weight loss, painless obstructive jaundice and diarrhea. Somatostatinoma syndrome occurs in those with a functioning pancreatic SSoma with manifestations including diabetes mellitus, cholelithiasis, diarrhea, weight loss, steatorrhea and hypochlorhydria. More than half of all SSomas are malignant and they have often metastasized at the time of diagnosis. Duodenal somatostatinoma is often associated with neurofibromatosis type 1 (NF1; see this term).

Etiology

Some SSomas are components of familial endocrine tumor syndromes. The cause of sporadic SSomas is not clear. SSoma hypersecretes stomatostatin, which inhibits the secretion of numerous gastrointestinal hormones (such as gastrin, secretin, insulin, glucagon, and cholecystokinin), resulting in somatostatinoma syndrome