IMMUNOCYTOCHEMICAL CHARACTERIZATION OF MALIGNANT MESOTHELIOMA AND CARCINOMA METASTATIC TO THE PLEURA - IOB3 - A NEW TUMOR-MARKER

We have tried to find a reliable panel of markers that would allow dis tinction between mesotheliomas and carcinomas metastatic to the pleura . In a prospective study, we evaluated 54 pleural effusions: In 27 of the patients, a diagnosis of histologically proven metastatic carcinom a was subsequently established, 7 patients had biopsy-proven malignant mesotheliomas and 20 had benign, reactive effusions whose benign etio logies were established by more than 2 years clinical follow-up. The M Ab (monoclonal antibody) IOB3 proved to be diagnostic for carcinomas i n all 27 cases (100%), whereas CEA (carcinoembryonic antigen) expressi on was found in only 22 out of 27 (81%). None of the malignant mesothe liomas, nor benign reactive mesothelial cells reacted with these two m arkers. All carcinomas, as well as one malignant mesothelioma, reacted with the MAb HEA125. Antibodies against 12 single cytokeratins, vimen tin, and EMA (epithelial membrane antigen) were not helpful in the dif ferentiation between malignant mesotheliomas and malignant carcinomato us pleural effusions. We conclude that adding the antibody IOB3 to the CEA assay should allow a reliable differentiation between these two e ntities.