Intraductal tubular adenoma of the pancreas, pyloric gland type: a clinicopathologic and immunohistochemical study of 6 cases.

The intraductal tubular adenoma (ITA), pyloric gland type, of the pancreas is an uncommon benign tumor, akin to the pyloric gland type adenoma of the gallbladder. We report 6 cases of ITA of the pancreas: 3 male and 3 female aged 50 to 79 years (mean, 63.5 years; median, 65 years); all were examined clinicopathologically. Four patients showed no symptoms, but appetite loss and/or general fatigue presented in two. Grossly, all tumors formed a localized polypoid mass protruding into the lumen of the dilated pancreatic duct. Five of the six tumors were found within the main duct, and the other arose within the branch duct of the pancreas. Microscopically, the tumors were composed of closely packed tubular glands resembling pyloric type glands. They were lined by columnar or cuboidal epithelial cells with foci of mild to moderate dysplastic change. In 2 cases, the adjacent pancreas showed foci of intraductal papillary-mucinous adenoma. Histochemically, the tumors largely showed neutral mucin with a lesser amount of acidic mucin made up mainly of sialomucin. Endocrine cells were found in five tumors. Immunohistochemically, all tumors were labeled with M-GGMC-1 and MUC6, whereas MUC1 and MUC2 stains were negative. Pepsinogen II was positive in 5 tumors; thus, the results displayed a pattern of differentiation similar to those of ordinary gastric pyloric or metaplastic pyloric glands. DPC4 expression was maintained in all tumors and p53-positive nuclei were hardly encountered. All patients are alive with no evidence of disease 3 to 10.5 years after surgical resection.