Value of BCA-225 in the cytologic diagnosis of malignant effusions: an immunocytochemical study of 197 cases.

An immunocytochemical study of routinely prepared paraffin embedded cell block material from 72 effusions containing adenocarcinoma and 125 benign effusions was performed using a commercially available monoclonal antibody to the breast carcinoma associated glycoprotein BCA-225. Positive staining was observed in cells in 77.8% of the malignant effusions but not in any of the benign effusions. We conclude that BCA-225 is a highly specific and very useful discriminator in the differential diagnosis of adenocarcinoma and reactive mesothelial cells. However, because this marker is not expressed in all adenocarcinomas, studies with a panel of antibodies will provide better sensitivity.