A Comparative Study of Cytomorphology and Flow Cytometry to Detect Malignant Cells in the Body Cavity Fluid
Wasithep Limvorapitak MD*, Orathai Promsuwicha MSc*, Chirayu U Auewarakul MD, PhD*
Affiliation : * Division of Hematology, Department of Medicine, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
Background : Many types of cancer metastasize to the epithelial linings of the body cavity causing malignant fluid to
accumulate in such spaces. Cytomorphological evaluation is considered essential in the diagnosis of malignant body fluid.
Nevertheless, the accuracy of cytomorphological results is subjective and can vary depending on the cytopathologists’
experience.
Objective : To determine if DNA content analysis using propidium iodide (PI), anti-CD45 (leukocyte common antigen) and
anti-AE1/AE3 (pan-cytokeratin) as analyzed by flow cytometry could be used to detect and differentiate malignant cells in the
body fluid when compared to cytomorphological evaluation.
Material and Method: A cross-sectional, laboratory-based, observational study on 90 specimens was conducted. Flow
cytometric analysis was done. Sensitivity, specificity, positive predictive value, negative predictive value and accuracy were
reported.
Results : The DNA index (DI) cut-off value, as determined by the receiver operating characteristic curve of 1.215 or more, had
51.7% sensitivity and 89.1% specificity to detect malignant cells. When DI was combined with AE1/AE3 positivity, the
sensitivity increased to 62.1% with 80.3% specificity. When such techniques were used in adjunct to cytospin preparation, the
sensitivity and specificity increased to 89.7% and 65.6%, respectively. Twelve specimens (13.3%) had positive results by flow
cytometry but negative cytomorphological results by pathologists, 4 of which were later confirmed as cancer from pleural
biopsy. Eleven specimens (12.2%) had false negativity, 6 of which were unspecified metastatic carcinoma. Four specimens
with negative flow cytometric results were cerebrospinal fluid (CSF) specimens with a low cell count. Subgroup analysis in the
cases of non-CSF fluid showed 72% sensitivity and 72.1% specificity.
Conclusion : Immunophenotypic analysis using DI and AE1/AE3 in conjunction with cytospin preparation had a moderately
high sensitivity to detect malignant cells in the body fluid (~90%). Non-CSF specimens yielded better results than CSF. Further
modifications are ongoing in order to increase the detection capabilities of our screening panel.
Keywords : Body cavity fluid, Flow cytometry, Effusion, DNA content analysis, Cytomorphology
