Application of the International System for Reporting Serous Fluid Cytopathology (ISRSFC) in reporting serous effusion: A retrospective study

Abstract

In order to develop uniform diagnostic standards and reporting terminology, the International Academy of Cytology and the American Society of Cytopathology have recommended the establishment of the International System for Reporting Serous Fluid Cytopathology (ISRSFC). ISRSFC has 5 diagnostic categories: non-diagnostic (ND), negative for malignancy (NFM), atypia of unknown significance (AUS), suspicious for malignancy (SFM), and malignant (MAL). So far, very few studies have evaluated the risk of malignancy (ROM) and performance characteristics (sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy) of different categories. The purpose of this study was to reclassify serous effusions based on the ISRSFC and to assess their ROM and performance characteristics. All serous effusions from January 2017 to December 2022 were categorized according to the ISRSFC. Using histopathological diagnosis as the gold standard, the ROM and performance characteristics were calculated for each group. Finally, a total of 2103 serous effusion specimens were analyzed. After reclassification, 9 (0.4%) cases were classified as ND, 547 (26%) as NFM, 94 (4.5%) as AUS, 386 (18.4%) as SFM, and 1067 (50.7%) as MAL. The ROMs for ND, NFM, AUS, SFM and MAL were calculated to be 50%, 24.9%, 36.8%, 89.0%, and 100%, respectively. As an easy-to-grasp reporting system, ISRSFC provides a consistent standard for better communication between physicians and pathologists.