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

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.

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.

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.

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.