Cytokeratin expression in hepatocellular carcinoma: an immunohistochemical study

Normal human hepatocytes express cytokeratins no. 8 and 18, whereas bile duct cells contain the same cytokeratins and, in addition, cytokeratins no. 7 and 19. This cytokeratin pattern is believed to be preserved during neoplastic transformation. Thirty-four cases of hepatocellular carcinoma (11 well differentiated, 16 moderately differentiated, 7 poorly differentiated) were studied on frozen sections using monoclonal antisera directed against individual cytokeratins no. 7, 8, 18, and 19 in an immunoperoxidase procedure. In 17 of 34 cases, tumor cells showed only reactivity with monoclonals anticytokeratin no. 8 and 18. However, 17 of 34 cases showed an aberrant pattern in that a variable number of tumor cells were stained with anticytokeratins no. 7 and/or 19 in addition to no. 8 and 18. Only three of 11 well-differentiated cases displayed an unexpected cytokeratin pattern, whereas an aberrant pattern was present in all seven of seven poorly differentiated cases. These results are in conflict with previously published data obtained by two-dimensional gel electrophoresis and immunohistochemistry. They indicate that the cytokeratin pattern might not always be preserved during neoplastic transformation. The implication of this finding for the differential diagnosis of metastatic gastrointestinal carcinomas is discussed.