Ber-EP4 for differentiating adenocarcinoma from reactive and neoplastic mesothelial cells in serous effusions. Comparison with carcinoembryonic antigen, B72.3 and Leu-M1.

OBJECTIVE

To evaluate the efficacy of Ber-EP4 in distinguishing epithelial cells from mesothelial cells in routine cytologic preparations.

STUDY DESIGN

Paraffin-embedded cell blocks of serous effusions from 32 patients (11 metastatic adenocarcinomas, 16 reactive mesothelial proliferations and 5 malignant mesotheliomas) were immunostained with Ber-EP4. For comparison, cell block preparations of adenocarcinomas and mesotheliomas were also immunostained with the most commonly applied markers of adenocarcinoma: carcinoembryonic antigen (CEA), B72.3 and Leu-M1. In addition, cytocentrifuge preparations of 14 reactive effusions and 2 metastatic adenocarcinomas were stained prospectively with Ber-EP4.

RESULTS

All adenocarcinomas showed intense membrane staining, while all mesothelial proliferations, both benign and malignant, were negative. The Ber-EP4-positive immunostaining was remarkably clean, with very minimal nonspecific staining. CEA stained 11/11 adenocarcinomas, B72.3 stained 10/11, and Leu-M1 stained 8/11; mesotheliomas were negative with all three antibodies.

CONCLUSION

Ber-EP4 is at least as useful as CEA, B72.3 and Leu-M1 in the diagnosis of serous effusions. It has the advantage of high sensitivity and ease of interpretation because of the high percentage of tumor cells stained, characteristic membranous staining and lack of cross-reaction with background inflammatory cells.