A simplified flow cytometric immunophenotyping procedure for the diagnosis of effusions caused by epithelial malignancies.

Epithelial malignancies frequently metastasize to the serous cavities and result in symptomatic effusions. Cytology has high specificity but moderate sensitivity for the diagnosis of a malignant effusion. We developed and validated a simple, rapid, 3-color flow cytometric panel using the adhesion molecule Ber-EP4 to detect epithelial cells in effusions. One hundred ninety-five consecutive benign and malignant effusions received for routine cytologic examination were analyzed. Eighty-three fluid specimens were benign and 76 were malignant as judged by follow-up data. Ber-EP4-positive cells were detected with flow cytometry in 89.3% of malignant effusions. The sensitivity and specificity of flow cytometry was 88.15% and 97.64% compared with 73.68% and 100% on cytologic examination alone for the presence of a malignant effusion. Flow cytometry is a useful adjunct to cytology for the diagnosis of a malignant effusion and is particularly useful if the cytologic diagnosis is atypical/suspicious or if the cytologic preparations are hypocellular or hemorrhagic.