A Case Report of Multiple Endocrine Neoplasia Type 1 with Duodenal Microgastrinoma and Pancreatic Insulinoma

A 42-year-old man complained of epigastric discomfort after gastrectomy for a duodenal ulcer. Endoscopic examination revealed an anastomotic ulcer. Blood chemistry tests revealed hypergastrinemia, hyperPTHemia, hypercalcemia, and hyperprolactinemia. The fasting plasma insulin level was within normal limits, but the postprandial plasma insulin level was very high. We detected tumors in the pituitary gland, parathyroid gland, and pancreas, so we madea diagnosis of multiple endocrine neoplasia type 1. Computed tomography and ultrasonography of the abdomen revealed that the pancreatic tumor was solitary and located in the pancreatic head. Pancreaticoduodenectomy was performed, and we detected a solitary tumor in the pancreatic head. Histological examination of the resected specimen revealed tumors not only in the pancreatic head but also in the duodenal wall. The duodenal tumors were very small and multiple, and could not be detected during the operation. Immunohistochemical study and mRNA expression of these tumors suggested that insulin was produced in the pancreatic tumor and gastrin was produced in the duodenal microtumors.