THE VALUE OF ANTI-CALRETININ ANTIBODY IN THE DIFFERENTIAL-DIAGNOSIS OF NORMAL AND REACTIVE MESOTHELIA VERSUS METASTATIC TUMORS IN EFFUSION CYTOLOGY

In effusion cytology the distinction of reactive mesothelia from metas tatic carcinoma cells may be a diagnostic challenge. Immunocytochemist ry using antibodies suit able to detect epithelial cells must be consi dered carefully due to Limited sensitivity and specifity of these anti bodies. Efficient results in histological differential diagnosis of ma ligant mesothelioma versus lung-adenocarcinoma applying a novel antise rum against the calcium binding protein calretinin inspirated us to in vestigate the value of anti-calretinin antibody in effusion cytology c ombined with an epithelial marker. Cytoslides prepared by cytocentrifu gation from 42 malignant and 65 reactive effusion specimens were immun ostained using antibodies against calretinin and the epithelial marker Ber-EP4. Positive immunoreaction for calretinin in normal and reactiv e mesothelial cells was noted in 93% of the cases, whereas immunoreact ion for calretinin was completely negative in the metastatic cells in 95% of the malignant effusions. Metastatic carcinoma cells were detect ed with anti-Ber-EP4 in 83% of malignant effusions. Non-specific posit ive reactions for Ber-EP4 in single mesothelial cells were observed in 16% of all cases and, moreover, frequently with macrophages or neutro philic granulocytes. Our results demonstrate high sensitivity and spec ifity of anti-calretinin antibody for mesothelial cells in effusion sp ecimens. They support its application to improve the diagnostic reliab ility of epithelial markers, especially because anti-calretinin antibo dy could be helpful in the assessment of false positive and false nega tive reactions of epithelial markers.