Methods: In this study, 67 malignant mesothelioma, 18 reactive mesothelial hyperplasia, and 33 metastatic adenocarcinoma specimens were examined and stained with epithelial membrane antigen.

Results: Staining with epithelial membrane antigen was observed in 45 of 67 malignant mesotheliomas cases (68.7%) and all the metastatic adenocarcinoma cases (100%). All metastatic adenocarcinomas showed prominently expressed epithelial membrane antigen, whereas weak positivity with epithelial membrane antigen was detected in only one case with reactive mesothelial hyperplasia. Metastatic adenocarcinoma showed a statistically significantly stronger expression compared to mesothelial hyperplasia (p<0.001). Sensitivity and specificity for malignant and benign cases were 78% and 94%, respectively.

Conclusion: Epithelial membrane antigen is a useful positive marker of malignant mesothelioma and metastatic adenocarcinoma. Also, it plays a significant role in distinguishing neoplastic mesothelium from non-neoplastic mesothelium.