Keratins in malignant mesotheliomas and pleural adenocarcinomas: comparative immunohistochemical analysis with polyclonal and monoclonal antibodies.

The distribution of intra-cellular keratins was studied in normal pleural mesothelium, malignant mesotheliomas and adenocarcinomas. This study was performed on deparaffinized sections of tissue fixed in Bouin's solution by indirect immunofluorescence with a monoclonal antibody (KL1) and a conventional keratin antiserum (AKS). Discrepancies were detected using one antibody or the other. Cells from normal mesothelium and 18 cases of malignant mesotheliomas (papillary, tubulary, solid epithelial type) were strongly labelled only by KL1. The 2 cases of sarcomatoid type were negative with both antibodies. In contrast 5 metastatic adenocarcinomas and 5 lung adenocarcinomas were weakly positive or negative with both antibodies. These data confirm the presence of cytokeratins in epithelial differentiation process. Although a clear-cut distinction between mesotheliomas and adenocarcinomas was not possible using these keratin antibodies. Our data point out the importance of reactivity pattern of the antibody used in such investigations.