Somatostatin secreting tumors, also referred to as somatostatinomas or SSomas, are neuroendocrine tumors of D-cell origin that may synthesize, deposit, or secret somatostatin. Somatostatin is a peptide that uses paracrine signaling to inhibit secretion of insulin, glucagon, gastrin, and growth hormone. Somatostatinomas are extremely rare and are reported to occur in less than 1 in 40 million people. Somatostatinomas typically occur in patients between 50 and 55 years of age. Around half of somatostatinomas develop in the pancreas, with the next most common sites being the ampullary and periampullary duodena.

Somatostatinomas are associated with multiple endocrine neoplasia type 1 (MEN1) syndrome and neurofibromatosis type 1 (NF1); up to 45% of somatostatinomas occur in association with MEN1, and up to 10% of patients with NF1 develop duodenal somatostatinomas.

The majority of somatostatinomas are identified incidentally. When symptomatic, the most common symptoms are abdominal pain, weight loss, and jaundice due to local mass effect. Patients with functional pancreatic somatostatinomas may present with diabetes, cholelithiasis, diarrhea, steatorrhea, and anemia, although this "somatostatinoma syndrome" is present in less than 10% of these tumors. The diagnosis of somatostatinoma is supported by an elevated serum somatostatin level. Histologically, a somatostatinoma will demonstrate a neuroendocrine tumor, often with immunoreactivity for somatostatin.

The majority (40%-92%) of patients with somatostatinomas present with metastatic disease. Relative 10-year survival for pancreatic neuroendocrine tumors is 8.9%.