[Malignant mesothelioma of the pleura. Analysis of its immunohistochemical aspects].

To evaluate the usefulness of immunohistochemistry in the diagnostic distinction between pleural mesothelioma and metastatic adenocarcinoma to the pleura, the authors studied formalin-fixed paraffin-embedded tissue sections from 14 pleural mesotheliomas and 20 primary adenocarcinomas of the lung, stomach, ovary and breast by using 16 commercially available antibodies to cytokeratin (KL1), vimentin, EMA, CEA, CA19.9, CA125, Egp 34 (detected by HEA 125), secretory component, S100 protein, SP1-béta 1, Leu M1, alpha-1-AT, alpha-1-ACT, lysozyme, desmin and factor VIII. Keratin positivity was found in all mesotheliomas and adenocarcinomas. A coexpression of keratin and vimentin was present in 8/14 (57%) mesotheliomas but only in 2/20 (10%) adenocarcinomas. CEA and CA 19.9 were detected in 80% and 65% of the adenocarcinomas respectively, but not in any of the mesotheliomas. Interestingly, two adenocarcinomas (of the ovary and the stomach) that failed to stain for CEA, were immunoreactive to anti-CA 19.9 antibody. Thus, the combined use of anti-CEA and anti-CA 19.9 antibodies results in staining 90% of the adenocarcinomas. S100 protein, SP1-beta and Leu M1 were also absent in mesotheliomas but present only in less than half of the adenocarcinomas. Adenocarcinomas and mesotheliomas did not significantly vary in reaction to the remaining above mentioned antibodies. The authors conclude that the coexpression of keratin and vimentin and the absence of CEA and CA 19.9 might be the best criteria in the distinction of mesothelioma from metastatic non mucosecreting adenocarcinoma.