Detection of monocyte/macrophage cell populations in effusions: A comparative study using flow cytometric immunophenotyping and immunocytochemistry

The objective of the present study was to compare the efficiency of immunop henotyping using flow cytometry (FCM) and inummocytochemistry (ICC) in the detection of macrophages in serous effusions. Cytoblock sections from 90 ef fusions were stained for the monocyte/macrophage marker CD14, using ICC. Fr esh-frozen samples of all cases were analyzed for CD14 expression, using FC M. Epithelial, lymphoid, and mesothelial cell populations were identified u sing antibodies against Ber-EP4, CD45, and N-cadherin, respectively. Result s were compared with clinical parameters and morphological diagnosis. Thirt y-nine specimens were cytologically diagnosed as malignant, containing tumo r cells of nonhematologic origin, whereas 46 were interpreted as benign. Tw o additional specimens were diagnosed as indeterminate or suspicious for ma lignancy, and 3 specimens contained lymphoma cells. CD14-positive cells wer e detected in 85/90 (94%) of effusions using FCM and in all 90 specimens us ing ICC. the detection of CD14-positive cells (P < 0.001). The presence of macrophages in effusions showed an association with female gender, using bo th FCM (P = 0.002) and ICC (P = 0.011), but none with effusion site, patien t age, clinical and cytological diagnosis, or presence of Ber-EP4-positive cells (P > 0.05). The presence of Ber-EP4-positive cells showed a strong as sociation with the cytological diagnosis of malignancy (P < 0.001). In conc lusion, macrophages are a significant cell population in effusions, of both benign and malignant etiology, due to both their size and their possible c onfusion with cancer cells. Both FCM and ICC aid in the recognition of thes e cells, and thus provide an effective tool for the identification of diffe rent cell populations in effusions.(C) 2001 Wiley-Liss, Inc.