Value of the MOC-31 monoclonal antibody in differentiating epithelial pleural mesothelioma from lung adenocarcinoma.

MOC-31 is a monoclonal antibody that has recently become commercially available that recognizes an epithelial-associated, transmembrane glycoprotein often expressed in epithelial tumors. Although some authors have indicated that MOC-31 immunostaining can assist in distinguishing epithelial mesotheliomas from metastatic adenocarcinomas to the pleura, others have concluded that this marker has no value in separating these conditions. To determine whether MOC-31 immunostaining can assist in discriminating epithelial pleural mesothelioma from lung adenocarcinoma or from other carcinomas metastatic to the pleura, 38 epithelial pleural mesotheliomas, 40 pulmonary adenocarcinomas, 55 nonpulmonary adenocarcinomas, six squamous cell carcinomas of the lung (SCCLs), three small-cell lung carcinomas (SCLCs), 19 bronchial carcinoids (BCs), and 15 transitional cell carcinomas (TCCs) were studied. Reactivity was obtained in two (5%) of the mesotheliomas, in all 40 (100%) pulmonary adenocarcinomas, in 45 (82%) nonpulmonary adenocarcinomas, in six (100%) SCCLs, three (100%) SCLCs, 15 (83%) BCs, and 10 (67%) TCCs. The staining in the two positive mesotheliomas was restricted to a few cells, in contrast to the pulmonary adenocarcinomas and most of the other carcinomas where it was often strong and diffuse. It is concluded that MOC-31 can be useful in separating epithelial pleural mesothelioma from pulmonary adenocarcinoma or from other epithelial malignancies involving the pleura.