Immunohistochemical expression of cytokeratins in intrahepatic cholangiocarcinoma and metastatic adenocarcinoma of the liver

Background and Objectives: This study was designed to identify a difference in immunostaining that might help to distinguish between primary and metas tatic liver neoplasms. Methods: We examined immunohistochemical expression of cytokeratins (CKs) 7 , 8, 19,and 20 in 12 intrahepatic cholangiocarcinomas (ICCs; 9 of the mass- forming and 3 of the infiltrating type), 25 metastatic colorectal carcinoma s (MCCs), and 7 metastatic gastric carcinomas (MGCs) of the liver. Results: CKs 7 and 19 were expressed in all ICCs of infiltrating type, whil e each was seen in 7/9 (77.8%) of mass-forming type. CK 7-positive/CK 20-ne gative was seen in 9/12 (75.0%) of ICCs and in none of the 25 MCCs, while C K 7-negative/CK 20-positive was seen in 1/12 (8.3%) of ICCs and 20/25 (80.0 %) of MCCs. No differences were observed between MGCs and ICCs. Conclusions: These results suggest that immunohistochemical staining for bo th CKs 7 and 20 is useful for the differential diagnosis of ICCs and MCCs, whereas phenotypic expression of CKs appears to be different between mass-f orming and infiltrating types of ICCs. (C) 1999 Wiley-Liss, Inc.