CYTOKERATIN PROFILE OF EXTRAHEPATIC PANCREATICOBILIARY EPITHELIA AND THEIR CARCINOMAS - DIAGNOSTIC APPLICATION

Carcinomas of the ampullary region and pancreatic head are morphologic ally similar and often indistinguishable even after careful convention al pathologic evaluation. Using a microwave antigen retrieval techniqu e on formalin-fixed, paraffin-embedded tissue and monoclonal antibodie s to each of cytokeratin (CK) subtypes CK7, CK8, CK18, CK19, and CK20, we investigated and compared the CK profiles of the pancreaticobiliar y and duodenal epithelia with those of 22 carcinomas arising from them . Microwave antigen retrieval was effective in restoring CK antigenici ty to formalin-fixed, paraffin-embedded archival tissues. Both the nor mal pancreaticobiliary epithelium and the carcinomas arising from them expressed CK7, CK8, CK18, and CK19 but not CK20. By contrast, the duo denal villous epithelium and four of five ampullary carcinomas express ed CK20 strongly. Reactivity for CK7, absent in the duodenal/ampullary epithelium, was seen in only one of the five ampullary carcinomas. Th e immunophenotype CK7+/CK20- or CK7-/CK20+ permitted an accurate ident ification of the site of origin for 14 of 22 carcinomas in this region . Our study therefore indicates that carcinomas of this region recapit ulate the CK profiles of their parent epithelia in a diagnostically us eful way. Carcinomas of duodenal origin (CK7-/CK20+) can often be reli ably distinguished from pancreaticobiliary carcinoma (CK7+/CK20-) on t he basis of their immunoreactivity to CK7 and CK20.