Accuracy of immunohistochemistry in evaluation of malignant pleural and peritoneal effusions

Background: The aim was to evaluate the accuracy of immunohistochemistry in diagnosis of the source of malignancies in pleural and peritoneal fluids in comparison to histopathology as the gold standard.

Material and methods: Retrospectively, the cell block specimen and past medical data files of patients who had undergone serosal fluid aspiration and had a histopathology report corresponding to underlying disease were retrieved. Three mesothelial antibodies (D2-40, calretinin and WT-1) and two non-mesothelial antibodies (MOC-31 and EMA) were set to be applied for evaluating malignant cells and benign cells within serous fluids.

Results : Seventy-one patients, 12 men and 59 women, were found to have a thorough information package needed, including cell blocks with appropriate cellularity on which ICC was applicable and the corresponding histopathology report. As mesothelial markers, calretinin and WT-1 were found to have sensitivity and specificity of 90%, 96.7% and 100%, 42.6%, respectively. Sensitivity and specificity of D2-40 both reached 100%. In addition, as non-mesothelial markers, MOC-31 and EMA were demonstrated to have sensitivity and specificity of 95.08%, 90% and 93.4%, 70%, respectively.

Conclusion : D2-40 was reconfirmed to act as an accurate marker in distinguishing between cells of mesothelial and non-mesothelial origin. However, WT-1 is not specific enough to be considered as accurate as D2-40. Considering the sensitivity and specificity of calretinin and MOC-31, they can be considered as safe but not as much as D2-40. EMA is not recommended as an ancillary marker due to its low specificity and challenging results.