A Retrospective Analysis of the Application of the Newly Proposed International System for Reporting Serous Fluid Cytopathology on Serous Effusion Specimens: An Institutional Experience

Introduction: The International Academy of Cytology and the American Society of Cytopathology recently proposed the International System for Reporting Serous Fluid Cytology (ISRSFC) to standardize serous fluid cytopathology reporting and guide further clinical management. The current study aimed to assess the feasibility of utilizing ISRSFC reporting categories for serous fluids, estimate the risk of malignancy (ROM) of each category, and scrutinize if the management protocols followed in our institution are as per the ISRFSFC recommendations. Methods: All pleural, peritoneal, and pericardial effusions submitted for evaluation at our institute between January 2021 and December 2021 were retrieved. All these cases were reviewed and re-categorized into one of the five categories proposed by the ISRSFC: non-diagnostic (ND), negative for malignancy (NFM), atypia of uncertain significance (AUS), suspicious for malignancy (SFM), and malignant (MAL), and ROM was calculated for each category. Results: The present study examined 596 serous effusions, of which 229 were pleural effusions, 358 were peritoneal effusions, and the remaining nine were pericardial effusions. Among 596 cases, 395 cases had a radiological or histological follow-up. The serous effusion samples were re-categorized as 61 (10.2%) ND, 449 (75.3%) NFM, 47 (7.8%) AUS, 17 (2.9%) SFM, and 22 (3.8%) MAL, and ROM for each above category were 10%, 4.4%, 19%, 83.3%, and 100%, respectively. Conclusion: Categorizing serous effusion cytology samples per the ISRSFC diagnostic categories reduces reporting variability. The ISRSFC provides a standardized format to predict the ROM and thus improves the quality of clinical care.