The value of cytology in distinguishing malignant mesothelioma: An institutional experience of 210 cases reclassified according to the International System for Reporting Serous Fluid Cytopathology (ISRSFC)

Objective Malignant mesothelioma (MM) is usually diagnosed by histological examination of tissue samples; however, effusion cytology offers an opportunity to identify a strong possibility for mesothelioma diagnosis at an early stage. We conducted a retrospective analysis of cytological specimens from a large series of histologically proven MM diagnosed over 19 years. The cases were reviewed and reclassified according to the International System for Reporting Serous Fluid Cytopathology (ISRSFC). Methods A total of 450 cases were identified. Cytological analysis was present in 210 patients (164 pleural and 46 peritoneal effusions). All cases were reviewed and reclassified according to the proposed ISRSFC scheme. A comparison among the cytomorphological features was made throughout the different diagnostic categories. Results The 210 cases were histologically diagnosed as follows: 192 (91.4%) cases had an epithelioid type and 18 (8.6%) had a sarcomatoid subtype of MM. The cytological cases were reclassified as follows: 2 (0.9%) as non-diagnostic (ND), 81 (38.6%) as negative for malignancy (NFM), 4 (1.9%) as atypia of undetermined significance (AUS), 11 (5.2%) as suspicious for malignancy (SFM), 112 (53.4%) as malignant (MAL). Sarcomatoid cells in the MAL category were characterised cytomorphologically by more pronounced discohesion. In comparison with the epithelioid subtype, the tumour cells appeared solitary with moderate or marked nuclear pleomorphism, and irregular chromatin. Conclusions It is important to recognise the cytological characteristics of this aggressive entity to suggest an early and precise possible diagnosis. Morphological features, coupled with clinico-radiological data may help the clinicians in adequately managing the patients.