Diagnostic Utility of Cell block and Immunocytochemistry in Differentiating Malignant from Non-malignant Effusions: A Cross-sectional Study

Abstract

Introduction: Cytological evaluation of body cavity fluids has been widely employed in diagnosing the underlying aetiology. Differentiating reactive mesothelial cell proliferations from metastatic malignant cells based on cytomorphology alone is challenging. Therefore, the use of cell blocks in conjunction with immunocytochemistry can significantly improve diagnostic accuracy. Aim: To investigate the role of cell blocks and immunocytochemistry in distinguishing malignant from non- malignant effusion fluids. Materials and Methods: A prospective cross-sectional study was conducted on 70 serous effusion fluid samples (ascitic and pleural fluids) received in the Cytology section of the Pathology Department from October 2021 to November 2022. Relevant clinical details, including demographic information, age, gender, presenting complaints, and radiological and laboratory investigations, were documented from the patients’ medical records. All fluids underwent conventional cytology, and the remaining fluid was used for cell block preparations. Immunocytochemistry was performed using Ber-EP4 and Calretinin immuno-markers to differentiate between reactive mesothelial cells and malignant cells. The association between cytosmear/cell block and immunocytochemistry was calculated using the chi-square test. Results: Out of the 70 cases, 44 were pleural fluids, and 26 were ascitic fluids. Conventional cytology identified 11 positive cases, 20 suspicious cases, and 39 negative cases for malignancy. However, after cell block examination, the total number of positive cases reduced to 9, suspicious cases decreased to 12, and negative cases increased to 49, resulting in a 14.3% increase in diagnostic accuracy. Immunocytochemistry using Ber-EP4 showed strong positivity in 12 cases, indicating epithelial malignancy (adenocarcinoma), while 9 cases were Ber-EP4 negative. Calretinin positivity was observed in the mesothelial cells of all 21 cases where immunohistochemistry was performed, resulting in a 17.5% increase in diagnostic accuracy. Conclusion: The combination of cell block technique with conventional cytology improves the diagnostic yield and accuracy by providing better interpretation of architectural patterns and cytomorphology. Additionally, the application of immunocytochemistry using Ber-EP4 and Calretinin aids in distinguishing malignant from non-malignant serous effusions.