Distended glands or overreplacement of ampullary mucosa at the papilla of Vater.

Background/purpose: The role of the ampullary mucosa, especially its distended glands at the papilla of Vater, has not been fully explored.

Methods: Twenty-nine pancreatoduodenectomized specimens from pancreatobiliary diseases and 44 autopsied cases, as controls, were studied histopathologically and immunohistochemically.

Results: In 12 out of the 29 pancreatoduodenectomized cases the ampullary mucosa was in contact with the duodenal mucosa just at the outlet of the ampulla. In the remaining 17 cases, the ampullary mucosa overgrew beyond the ostium, replacing a portion of the surrounding duodenal mucosa, termed "distended glands," which measured an average of 1532 microm in length. The muscularis mucosae of the duodenum and the Oddi's sphincter muscle merged in an "end-to-end, sharp-angled" manner at the ostium in the former, whereas this occurred in an "end-to-side, less sharp, rather right-angled" manner in the latter. Immunohistochemically, the distended glands in some cases showed negative/weakly positive staining for anti-carbohydrate antigen (CA) 19-9 and a high proliferation index evaluated using Ki67. In the autopsied materials, distended glands were found in 24 out of the 44 cases.

Conclusions: Distended glands of the ampullary mucosa were frequently found and only grew on the Oddi's sphincter muscle extension. They may represent not only malignant change but also an adaptive phenomenon for bile and pancreatic juice flow.