Large Duodenal Somatostatinoma in the Third Portion Associated with Severe Glucose Intolerance

A 51-year-old man was admitted with hyperglycemia and a duodenal tumor. Although his glycemic control was poor, basal C-peptide levels were not suppressed. Further examination revealed a mass measuring 7.8 cm in diameter in the third portion of the duodenum. Duodenectomy revealed a slow-growing sessile tumor located near Treitz’s ligament. The immunohistochemical profile of sections of the specimen revealed the presence of somatostatin. The patient’s serum somatostatin was elevated to 300 pg/ml preoperatively, but was reduced to 10 pg/ml postoperatively. Glycemic control also normalized after the operation.