Immunocytochemical staining of serous effusions with the monoclonal antibody Ber-EP4.

Cytospin preparations were made from 102 serous effusions for immunocytochemical staining using a panel of monoclonal antibodies including a new monoclonal antibody Ber-EP4. On cytological examination, 32 fluids were reported to contain tumour cells consistent with metastatic adenocarcinoma; 66 contained benign cells only and three were reported to contain cells suspicious of malignancy. One effusion contained tumour cells consistent with malignant mesothelioma. Positive staining of the tumour cells with Ber-EP4 was observed in the 32 effusions (100%) which contained adenocarcinoma cells. No staining of the mesothelial cells in these 32 specimens was observed. Carcinoembryonic antigen, epithelial membrane antigen Ca2 and CD15 staining of tumour cells was noted in 53%, 50%, 50% and 9% of these cases, respectively. None of the mesothelial cells in the benign effusions stained with Ber-EP4. Nor did the malignant mesothelial cells in the only case of malignant mesothelioma. These findings suggest that Ber-EP4 is a valuable addition to antibodies available for the differential diagnosis of mesothelial cells and adenocarcinoma cells in serous effusions.