Immunocytology in malignant pleural mesothelioma. Expression of tumor markers and distribution of lymphocyte subsets.

We studied the reactivity of malignant mesothelioma cells with tumor markers and the phenotypes of lymphocyte subsets in pleural effusions from 14 patients with malignant mesothelioma. For identification of cell surface antigens with monoclonal antibodies, the adhesive slide assay was used. The reaction pattern of mesothelioma cells was found to be CEA negative, Leu M1 negative, EMA positive, BMA-120 positive, My 4 positive, and BA-2 positive. The surface morphology of mesothelioma cells may be of additional help for diagnosis. By these markers, the distinction between mesotheliomas and carcinomas is facilitated. The differentiation of reactive benign mesothelial hyperplasia from malignant mesothelioma by surface marker staining is not yet possible, however. In many effusions in this study, a concomitant T-lymphocytosis was observed with a non-specific increase in the CD4/CD8 ratio, as known for other pleural diseases.