The cell adhesion molecule, E-cadherin, distinguishes mesothelial cells from carcinoma cells in fluids

Abstract

BACKGROUND: The distinction between benign reactive mesothelial cells and well differentiated carcinoma can be difficult in pleural, peritoneal, and especially pericardial fluids. E-cadherin is an adhesion protein that is specifically expressed in cells of epithelial lineage. In this study, anti-E-cadherin antibodies were used to identify and distinguish carcinoma cells from reactive mesothelial cells. METHODS: Pleural, peritoneal, and pericardial fluids were prepared using the Cytyc Thin Prep processor. The specimens were comprised of a mix of 45 cases that were diagnosed as carcinoma, suspicious, or reactive by Papanicolaou staining of routine material seen by the authors' service. Routine immunologic techniques were used with a commercially available E-cadherin antibody. RESULTS: In most cases of carcinoma, tumor cells showed a strong positive membranous reaction product (32 of 37). This included four cases that were not cytomorphologically diagnosed as malignant, but subsequently proved to be malignant. E-cadherin staining was not observed in five tumors, two of which were not expected to express this protein. One benign case showed cells staining for E-cadherin, although the cells were not malignant by morphologic criteria. Because this case was a surgical pelvic washing, these cells more likely were epithelial contaminants than true false-positives. CONCLUSIONS: The epithelial specific cell-cell adhesion marker E-cadherin reliably distinguishes reactive mesothelial cells from carcinoma and is a useful adjunctive test to distinguish benign reactive mesothelial cells from well differentiated carcinoma cells in fluid specimens.