Cytological diagnosis of malignant mesothelioma: A case series

Background: Mesotheliomas are neoplasms of the serosal lining of the body cavities. Diagnosis requires a multimodal approach of clinical findings, cytology, and histopathology with immunohistochemistry (IHC). The published sensitivity of cytology for diagnosing mesothelioma ranges from 30% to 75%. Aim and Objectives: This study aimed to calculate the incidence of malignant mesothelioma (MM) at our institute and to study the cytological features of MM. Materials and Methods: A retrospective study of pleural, peritoneal, and pericardial fluids submitted at our institute was done. The duration of the study was 8 years (2011-2019). Apart from examining Giemsa smears, a panel of immunocytochemical (ICC) and cell block immunohistochemical (IHC) markers was applied to achieve the diagnosis. These included calretinin, mesothelin, CK5/6, Hector Battifora mesothelial cell antibody (HBME), WT1, MOC31, CK7 and CK20. Histopathological correlation was done wherever possible. Result: In the present study, we compiled four cases of MM over 8 years diagnosed on serous effusion cytology and confirmed by immunocytochemistry (ICC)/cell block immunohistochemistry (IHC)/biopsy. This indicates a rare incidence of MM. The Cytological features of MM were studied. Conclusion: The diagnosis of MM is difficult, especially cytologically. It was found to be a rare entity in the malignant cases diagnosed on effusion cytology.