Detection of Malignant Epithelial Cells in Body Fluids: A Comparison of Flow Cytometry and Cytologic Evaluation
Heather D Morris, Nitin J Karandikar, Jyoti Balani, Franklin Fuda, Sara Monaghan, Jacqueline Emmons. UT Southwestern Medical Center, Dallas, TX
Background: It may be difficult to distinguish between carcinoma cells and reactive mesothelial cells by cytologic evaluation (CE) alone. Flow cytometry (FC) allows for evaluation of multiple antigens for a more complete characterization of individual cells. In this study, we tested the utility of FC in detecting carcinoma cells in body fluid specimens by staining for epithelial cell adhesion molecule (EpCAM).
Design: We prospectively analyzed 42 body cavity fluids by FC. Immunophenotyping was performed using antibodies against CD45, CD56, and EpCAM. FC was designated as positive, indeterminate, or negative based on EpCAM expression, with indeterminate cases showing only a few scattered EpCAM+/CD45- events. These results were compared to the CE of smear and cell block preparations by cytopathologists blinded to the results of the FC. Clinical data, including patient age, sex, history of malignancy, concurrent surgical specimen results and computed tomography (CT) scans, was gathered from the electronic medical record after FC analysis. The gold standard for determining a positive case was metastatic disease in either a surgical specimen or by CT.
Results: There were 17 gold standard-positive cases and 25 negative cases. CE diagnoses included 28 negative for carcinoma (Car-), 5 positive for metastatic carcinoma (Car+), and 9 atypical cells present (AtyC). All Car+ cases were also positive by FC. Among the 9 AtyC cases, FC was positive in 3 cases, all of which were positive by the gold standard. The remaining 6 AtyC were negative by flow cytometry and confirmed as negative by the gold standard. FC was negative in 24 of the 28 Car- cases. The remaining four Car- cases were designated as indeterminate by FC. All of these patients had evidence of an epithelial neoplasm (2 diagnosed with carcinoma; 1 serous cystadenoma; and 1 hilar mass on CT with history of lung carcinoma). Overall, FC showed 53% sensitivity and 100% specificity as compared to 29% sensitivity and 100% specificity by CE in detecting epithelial carcinoma. The negative predictive value was 76% by FC and 67% by CE.
Conclusions: FC is a rapid and highly effective tool for evaluating body fluids for malignant epithelial cells. Detection of a distinct cluster of EpCAM+, CD45- cells is strongly indicative of metastatic carcinoma. In equivocal cases by CE, FC can provide more definitive diagnostic results. Based on this study, FC is nearly twice as sensitive as CE for detecting metastatic carcinoma. The sensitivity of FC may be further improved with better understanding of the indeterminate cases.
Wednesday, March 21, 2012 9:30 AM
Poster Session V # 213, Wednesday Morning