Application of international system for reporting serous fluid cytology (ISRSFC) in effusion samples-a prospective study in an oncology setting

Serous fluid cytology is a cost-effective procedure that can help in the diagnosis, staging, and origin of the malignancy. Recently introduced International System for Reporting Serous Fluid Cytology (ISRSFC) standardizes the reporting of serous fluid cytology in the 5 categories: Category 1: Nondiagnostic (ND), Category 2: negative for malignancy (NFM), Category 3: atypia of undetermined significance (AUS), Category 4: suspicious for malignancy (SFM), and Category 5: malignant (MAL). Here, we present our experience adopting the ISRSFC. We implemented ISRSFC in December of 2019 at our institute and included a cohort of 555 prospective effusion samples. The pertinent surgical pathology, radiology, and clinical follow-up were also extracted to assess the risk of malignancy (ROM) and performance parameters. The assessment of interobserver reliability indicated substantial concordance (κ = 0.717) between the 2 investigators for serous fluid categorization. A total of 555 effusion samples were classified as follows: ND, 14 (2.5%); NFM, 394 (71%); AUS, 12 (2.2%); SFM, 13 (2.3%); and MAL, 122 (22%). The ROM for the ND, NFM, AUS, SFM, and MAL categories was 57.1%, 9.9%, 66.7%, 66.7%, and 97.2%, respectively, in peritoneal effusions and 57.1%, 7.1%, 66.7%, 100%, 100%, respectively, in pleural effusions. The ROM for NFM and MAL was 0% and 100%, respectively, in pericardial effusion. Application of the proposed ISRSFC can help in achieving uniformity and reproducibility in diagnoses and also help in risk stratification in cytology. ISRSFC was successfully adopted by our cytology laboratory and clinicians, with overall diagnostic performance similar to previous studies. •The International System For Reporting Serous Fluid Cytology is an internationally accepted system and provides the risk of malignancy for each of the diagnostic categories and clinical management.•The International System For Reporting Serous Fluid Cytology has been shown to be effective and helpful to communicate with a referring physician that ultimately improves patients care.•A triple test type of approach could be more helpful for the evaluation of effusions instead of relying upon radiological evidence or cytology in isolation for calculating performance parameters and risk of malignancy.•Serous membrane involvement (capsular and serosal breach) and distant deposits (omental and peritoneal metastasis) by histology is the best gold standard.