MUC5AC and invasive ductal breast carcinoma: The frequency for pancreatic adenocarcinoma inour study is somewhat lower than in previous studies showing MUC5AC expression in85% of 134 14 and 90% of 20 ductal adenocarcinomas.20 The 43% MUC5AC positivity seen for carcinomas of the ampulla Vateri is withinthe range of the results from earlier studies describing MUC5AC expression in 5%–62%in 6–90 evaluated cases.21, , , , , –27 Slightly discrepant resultsfrom IHC studies are to be expected as these studies used different antibodies, IHCprotocols, and cut-off levels for defining MUC5AC positivity.