Pyloric gland adenoma of the main pancreatic duct

A case of a pyloric gland type adenoma of the main pancreatic duct in a 69- year-old woman is reported. The tumor led to occlusion and cystic dilatatio n of the main duct in the pancreatic tail. The surgical resection specimen disclosed a polypoid, bilobed mass attached to the wan of the main pancreat ic duct by a thin fibrous stalk. Light-microscopic examination revealed a w ell-demarcated nodule composed of closely packed tubular glands lined by co lumnar, mucin-secreting cells with abundant clear cytoplasm and basally ori ented nuclei. Focal, mild cyto logic atypia was seen. Pyloric metaplasia an d focal papillary hyperplasia was present in the adjacent ductal epithelium . Periodic acid-Schiff reactions, with and without diastase predigestion, s howed reactivity in the tubular glands, whereas alcian blue (pH 2.5) was ne gative. Immunohistochemical stains for chromogranin, serotonin, somatostati n, and gastrin failed to detect the respective antigens. Genetic analysis u sing polymer ase chain reaction with mutant enrichment and allele specific oligonucleotide hybridization detected a single mutation at codon 12 of K-r as, which changed the wild-type glycine to arginine. This mutation is commo nly found in invasive pancreatic ductal carcinomas. Although tumors with mi croscopic and immunohistochemical features consistent with pyloric gland ad enoma have been described in the gallbladder, to our knowledge, this is the first reported case within the pancreatic ductal system. The finding of a K-ras, codon 12 mutation and the presence of focal dysplasia may denote neo plastic potential in association with this lesion.