Usefulness of ploidy, AgNOR and immunocytochemistry for differentiating benign and malignant cells in serous effusions.

Objective:  The objective of this study was to establish the value of different markers in differentiating reactive mesothelial cells from metastatic adenocarcinomatous cells in serous effusions (SE). Methods:  Forty-five SE were processed for morphological examination (Papanicolaou stain), assessment of ploidy, AgNOR counting and immunocytochemical assay of carcinoembryonic antigen (CEA), epithelial membrane antigens (EMA), Ber-EP4 and Leu-M1. Ploidy was established in an image-analyser in smears stained by the Feulgen stain method. AgNOR dots were counted in the smears stained with the silver nitrate assay for non-histone proteins present in the nucleolar organizer region. CEA, EMA, Ber-EP4 and Leu-M1 were evaluated by immunocytochemistry using the streptavidin–biotin complex method. Results:  All the smears with positive cytology were aneuploid. Three false negatives by morphological studies were aneuploid, with AgNOR values in two of them corresponding to the neoplastic group. CEA and Leu-M1 showed a low specificity; EMA and Ber-EP4 showed moderate sensitivity. Conclusions:  The assessment of ploidy and the study of AgNOR were better methods than immunocytochemistry for distinguishing between reactive mesothelial cells and adenocarcinomatous cells in serous fluid.