Quality Control of Immunocytochemical Staining of Effusions Using a Standardized Method of Cell Processing

OBJECTIVE: To improve the quality and reproducibility of immunocytochemical staining of effusions by using a standardized method of cell processing. STUDY DESIGN: The study included the specimens of 108 effusions (44 benign, 56 adenocarcinoma metastases and 8 mesotheliomas). Hemorrhagic effusions were lysed using isotonic ammonium chloride. All pellets were fixed in 1% paraformaldehyde dissolved in phosphate-buffered saline (PBS), pH 7.4, and washed in PBS. A Burker counting chamber was used to adjust the pellets to a standard cell concentration. The panel of monoclonal antibodies (MAbs) included MOC-31, Ber-EP4 and anticarcinoembryonic antigen (anti-CEA). The alkaline phosphatase/anti-alkaline phosphatase technique was applied. RESULTS: Standardized material processing resulted in reproducible specimens with good preservation of cell morphology, reduction of nonspecific interaction and good immunostain intensity. MAbs MOC-31 and Ber-EP4 gave similar results: both were positive in all adenocarcinomas. Anti-CEA was positive in 73%. Benign effusions showed no expression. In contrast to the literature, seven mesotheliomas showed variable membranous expression of MOC-31 and Ber-EP4. CONCLUSION: High-quality immunostaining results were obtained by using a standardized method of cell processing. MAbs MOC-31 and Ber-EP4 cannot be used as differentiation markers between mesotheliomas and adenocarcinomas. Discrepancies in immunocytochemical staining results may be caused partly by differences in cell preparation.