Somatostatinoma of the Ampulla of Vater

ABSTRACT

Somatostatinoma is a rare form of neuroendocrine tumor that was first described in 1977. Most tumors have involved the pancreas, and gastrointestinal tract involvement is rare. Somatostatinomas of the ampulla of Vater are extremely rare and present distinct clinical and pathologic differences. Pancreatic somatostatinoma has been associated with a clinical syndrome of dyspepsia, mild diabetes, cholelithiasis, steatorrhea, and hypochlorhydria, but duodenal somatostatinoma, in general, has been clinically silent. A further contrast is that duodenal carcinoid tumors, mainly gastrinoma, tended to be benign, whereas ampullary carcinoid tumors, mainly somatostatinoma, exhibited malignant behavior. Therefore, definite diagnosis is important for treatment and prognosis, and is performed by image study, immunohistochemistry and electron microscopic examination. We report a case of somatostatinoma of the ampulla of Vater in a 51-year-old male. He complained of generalized abdominal pain for a few days. Gastrofiberscopically, a 1.2 cm sized bulging mass was observed on the ampulla of Vater. Radiologically, on abdomen CT, a protruding enhancing mass was revealed in the duodenum. In octreoscan, there was an abnormal focus off increased radiouptake in the infrahepatic area. He underwent a pancreatoduodenectomy. Grossly, the mass was an intraluminary protruding polypoid submucosal mass with focal ulceration in the ampulla of Vater. Histologically, it showed well-differentiated nonpleomorphic tubular cell nest and psammoma bodies. Immunohistochemically, the tumor cells showed a neuroendocrine nature with synaptophysin immunostain and intense staining only for somatostatin.