Papillary adenoma of the stomach. Pathologic and immunohistochemical study.

A total of 13 gastric papillary adenomas composed of 8 papillary and 5 papillotubular adenomas were examined pathologically and immunohistochemically. They showed a dome-like or pedunculated appearance and were located at the antrum, except for one adenoma. Histologically, the adenoma cells showed atypia in varying degree and focal adenocarcinoma was noted in seven lesions. The number of goblet cells was apparently smaller in the papillary than in the tubular portion. Lysozyme was present at the supranuclear region in most papillary adenoma cells, whereas it was concentrated in Paneth's granules in tubular adenoma cells. No difference was found in the distribution and frequency of carcinoembryonic antigen, secretory component, and carbohydrate antigen CA 19-9 between papillary and tubular adenomas. Paucity of endocrine cells also characterized gastric papillary adenoma. Different phenotypic expressions might reflect the difference in histogenesis between papillary adenoma and tubular adenoma.