Gastric-type ampullary adenomas

Intestinal-type adenomas of the ampullary duodenum are well-characterized and recognized entities, sharing similar clinicopathologic features to conventional colonic adenomas. However, gastric-type adenomas arising from the duodenal ampulla are less recognized and characterized due to limited available data. Our main aim is to investigate the clinical, histopathologic, histochemical and immunohistochemical features of gastric-type ampullary adenomas. We aim to compare gastric-type adenomas with intestinal-type adenomas and inflammatory hyperplastic reactive-type polyps of the ampullary duodenum. We have conducted a retrospective review study of ampullary polyps over 15-years. We found 17 patients [age range: 22-84, average age: 51.0 years, male to female ratio: 1.1:1.0] with polypoid lesions of the ampullary duodenum. Four lesions (24 %) were gastric-type adenomas [age range: 46-84, average age: 63 years, male to female ratio: 1.0:3.0, average size: 1.0 cm], eight lesions (47 %) were intestinal-type adenomas [age range: 22-76, average age: 45 years, male to female ratio: 1.5:1.0, average size: 1.2 cm], and five lesions (29 %) were reactive inflammatory hyperplastic polyps [age range: 41-76, average age: 53 years, male to female ratio: 1.5:1.0, average size: 0.7 cm]. One of the gastric-type adenomas was pure pyloric gland adenoma, one was pure foveolar adenoma, whereas two were mixed adenomas showing equal proportions of foveolar and pyloric cytoarchitectural features. The foveolar adenoma showed luminal mucin cap and expressed MUC5AC, the pyloric gland adenoma lacked apical mucin cap and expressed MUC6, whereas the mixed adenomas equally coexpressed MUC6 and MUC5AC. The intestinal-type adenomas expressed MUC2 and CDX2, but lacked MUC5AC and MUC6. Three gastric-type adenomas were originally misinterpreted as reactive polyps, whereas two other reactive polyps were originally misinterpreted as intestinal-type adenomas. Three patients with gastric-type adenomas had multiple sporadic colonic adenomas, and one recurred. Four patients with intestinal-type adenomas had colonic adenomas, three of which had familial adenomatous polyposis with recurrence, and one had sporadic colonic adenomas with recurrence. The reactive polyps were not associated with colonic adenomas and did not recur. Gastric-type adenomas are not uncommon among ampullary polyps when carefully examined. They should be distinguished from reactive polyps, because similar to intestinal-type adenomas, they are neoplastic polyps with dysplasia and a risk of recurrence.