Duodenal somatostatinoma associated with diabetic ketoacidosis presumably caused by somatostatin-28 hypersecretion

Context: Extrapancreatic somatostatinoma is very rare and clinically distinguished from its pancreatic counterpart because somatostatinoma syndrome with mild diabetes is rare in extrapancreatic somatostatinoma because of poor secretion of somatostatin. Moreover, because somatostatin inhibits the secretion of insulin and glucagon simultaneously, true diabetic ketoacidosis (DKA) seldom ensues. Patient: A 23-yr-old woman presented with DKA and an abdominal mass. A computed tomography scan showed a huge, encapsulated mass in a duodenal submucous portion. A high circulating level of somatostatin was detected (67.2 pmol/liter; reference range, 0.6-7.3 pmol/liter). Intervention: The tumor mass was successfully removed with Whipple's procedure, and the patient gradually recovered both clinically and biochemically. Results: Immunohistochemical staining of the tumor tissue exhibited diffusely positive for somatostatin and somatostatin-28 but negative for insulin, glucagon, calcitonin, serotonin, and S-100. Conclusion: As far as we know, this is the first case report of gastrointestinal somatostatinoma associated with DKA.