Screening of carcinoma metastasis by flow cytometry: A study of 238 cases

Malignant epithelial cells may be detected in different specimens, by immunophenotyping using flow cytometry (FCM). CD326 (epithelial-specific antigen, clone Ber-Ep4) was used to identify epithelial cells, CD45 to discriminate between leucocytes (positive for this antigen) and non-hematological cells (negative for this antigen), and CD33 to identify monocytes/macrophages. This combination is particularly useful in effusions to characterize large cells and distinguish between monocyte/macrophages (CD45+ CD33+ CD326-), mesothelial cells (CD45 ± (dim) CD33 - CD326-) and epithelial cells (CD45 - CD33 - CD326 +). We evaluated the efficiency of flow cytometry to detect malignant epithelial cells in 238 fresh samples, including effusions, lymph node biopsies, fine needle aspirates, bone marrow aspirates, cerebrospinal fluid, among others. These are specimens expected to lack epithelial cells. FCM results were then compared to the results of smear and cell block morphology, as well as immunocytochemistry on paraffin wax embedded cell blocks, when available. Final diagnosis was the gold standard and a very good sensitivity (96.7%) and specificity (99.3%) were obtained. We concluded that the detection of CD326 positive cells using FCM is strongly indicative of the presence of carcinoma cells. © 2015 International Clinical Cytometry Society.