Clinical utility of flow cytometry in body fluid cytology: to flow or not to flow? That is the question

Flow cytometry, molecular analysis, and other special techniques (in Serous Fluid Cytopathology)

Morphological and architectural pattern evaluations play a major role in the rpretation of hematopoietic neoplasms. However, confirmation of diagnosis, classification, prognosis, and risk stratification are highly dependent on the utilization of multiple ancillary studies. The importance of these ancillary studies increases in evaluating serous fluid samples, as these samples lack architecture and patterns. Likewise, the morphology can be disturbed by sample preparation. The most common ancillary studies utilized are flow cytometry, immunohistochemistry for immunophenotyping, Fluorescent In Situ Hybridization (FISH), cytogenetics for structural and gene rearrangements, and molecular studies for mutational analysis. Among them, flow cytometry analysis is the handiest test to perform with high diagnostic yield on serous fluid specimens. In this article we will discuss the use, caveat, and role of the most common ancillary studies on serous fluid specimen evaluation. This review article will be incorporated finally as one of the chapters in CMAS (CytoJournal Monograph/Atlas Series) #2. It is modified slightly from the chapter by the initial authors (Choladda Vejabhuti, MD and Chung-Che (Jeff) Chang, MD, PhD) in the first edition of Diagnostic Cytopathology of Serous Fluids.

Diagnostic role of cytology in serous effusions of patients with hematologic malignancies

BACKGROUND

We investigated serous effusions occurring during the course of an already known hematologic neoplasia or as a first manifestation of it. We correlated cytology results with flow cytometry results, when available. In the absence of flow cytometry, our correlation was based on clinical follow up information obtained retrospectively. We evaluated our results in relation to the data of the literature and we considered some new suggestions for the improvement of cytology service.

METHODS

Serous effusions in hematologic patients were retrieved from the files of the Department of Cytology, Laiko Hospital, for a period of 2 years. All patients had enrolled either a previous hematologic history, or a suspicious clinical and imaging status. Seventy-three serous effusions were included. Cytology reports consisting of morphology and immunocytochemistry assessment were correlated to flow cytometry results and, occasionally, to clinical follow-up.

RESULTS

In the group of patients with previous history, sensitivity was 82.76%, positive predictive value was 100%, specificity 100%, and negative predictive value was 58.33%. In the group of patients without previous history, sensitivity and positive predictive value were both 91%, whereas specificity and negative predictive value could not be estimated.

CONCLUSION

We provide evidence that the diagnostic accuracy of cytology with the adjunct of immunocytochemistry is high compared to flow cytometry for detecting hematologic malignancies. In order to improve clinical performance, it is suggested that a cytology triage of serous effusions in all patients with hematologic malignancy must be implemented.

Utility of flow cytometry analysis for pleural and peritoneal fluids

INTRODUCTION

Pleural and peritoneal/ascites fluid samples with many lymphocytes are commonly received in the cytology laboratory. It is often difficult to distinguish reactive lymphocytes from hematopoietic malignancy based on morphology alone, however. Flow cytometry can be a useful adjunct in body fluids, although literature on this subject is limited.

MATERIALS AND METHODS

This study is a single-institution 5-year retrospective review of 377 fluid samples from 341 patients with corresponding flow cytometry analysis. The cytologic findings were correlated with the flow cytometry results and clinical data, as available.

RESULTS

Of 4158 pleural fluids received over 5 years, 325 (7.8%) had corresponding flow cytometry analysis. Of these 325 samples, 57 (17.5%) were positive for hematopoietic malignancy by flow cytometry. Of the positive cases, only 24 (8.7%) represented a new diagnosis of hematopoietic malignancy (ie, did not have a known history). Of 3020 peritoneal/ascites fluids received over 5 years, 52 (2%) had corresponding flow cytometry. Of these, 8 were positive for hematopoietic malignancy, and only 2 represented a presumed new diagnosis.

CONCLUSIONS

Routine flow cytometry analysis for pleural and peritoneal/ascitic fluids is of limited utility, with only rare cases positive for hematopoietic malignancy without a known history. Of these cases, many had atypical cells that suggested a positive diagnosis. Conversely, in cases with a known history, about 75% were positive for hematopoietic malignancy. Our study suggests that the utility of flow cytometry for pleural and peritoneal/ascitic fluids is limited, and should be used sparingly in cases without atypical cytologic features, high clinical suspicion, or known history.

Flow Cytometry and Effusions in Lymphoproliferative Processes and Other Hematologic Neoplasias

Cytopathologists are regularly confronted with lymphocyte-rich effusions, and the definite decision of whether the lymphocytosis is of a purely reactive nature or a presentation of an indolent lymphoma may be an extremely difficult one based on microscopy alone. Flow cytometry (FC) offers many advantages in terms of its application in body cavity fluids, and it has proven to be very useful both in the setting of a known disease and for new lymphoma diagnoses. In this paper, the studies published in recent years dealing with the applications of FC in body cavity effusions in the context of hematologic neoplasia are reviewed, stressing the integrative diagnostic approach. The incorporation of microscopical, immunophenotypical, and molecular findings from examinations of the cellular content of effusions and the interpretation of results in relation to the current WHO classification of hematolymphoid malignancies give cytopathologists new perspectives on advanced and clinically highly relevant diagnostics.

Comparison of urine cell characteristics by flow cytometry and cytology in patients suspected of having bladder cancer

The diagnosis of bladder cancer is confirmed by histological analysis of tissue biopsies. Cytology of urine samples is a noninvasive alternative. The aim of this work was to find out whether flow cytometry of urine samples is more sensitive than cytology. For this purpose we studied 115 patients suspected of having bladder cancer. Cells isolated from urine samples were analyzed by cytometry for the expression of cytokeratin and CD 45 and for DNA measurements such as: DNA index, synthesis phase fraction and proliferative index (SPF + G2/M phase). At the same time we carried out cytological analysis. All positive cases were confirmed by histology (21/115), 18 were diagnosed by flow cytometry and 16 by cytology, with a sensitivity of 85.7% and 76.1%, respectively. Two cases were found to be positive by flow cytometry, which were not confirmed by histology, while no false positives were detected by cytology. We found that both techniques gave almost identical results for the diagnosis of bladder cancer, although there were differences in non-malignant samples. In conclusion, flow cytometry is slightly more sensitive than cytology but the combination of the two techniques improves the diagnosis.