A minute nonfunctioning pancreatic endocrine tumor with ductal structures and prominent fibrous stroma: Report of a case

A 50-year-woman reporting general fatigue and found in abdominal ultrasonography to have a 1cm tumor in the body of the pancreas was suspected of pancreatic endocrine tumor because of contrast medium enhanced in CT. Abdominal MRI showed a low-intensity mass in the pancreatic body both in T1 and T2-weighted imaging unusual for an endocrine tumor. Serum CA19-9 was markedly elevated at 1,459.2U/ml, necessitating resection because pancreatic ductal carcinoma could not be ruled out. Histologically, the well-circumscribed tumor consisted of nests of endocrine tumor cells embedded in prominent fibrous stroma. The strong fibrosis appeared to cause the low intensity in T2-weighted MRI. The tumor had focally evident ductal structures and close contact with endocrine tumor cells. Immunohistologically, tumor cells were positive for chromogranin A and glucagon, but were negative for insulin, gastrin, and somatostatin. The ductal component was immunoreactive to CA19-9. The tumor was definitively diagnosed as nonfunctioning pancreatic endocrine tumor. Pathological findings in this case support the idea of pancreatic duct epithelia were differentiating into endocrine cells and ductal structures.