The International System for Reporting Serous Fluid Cytopathology: The Need for Version 2.0

Serous effusion cytopathology, of neoplastic and non-neoplastic origin, when feasible, should be coupled with ancillary procedures for the detection of malignancies. "The International System for Reporting Serous Fluid Cytopathology" (TIS) categorizes into nondiagnostic (ND), negative for malignancy (NFM), atypical cells of undetermined significance (AUS), suspicious for malignancy (SFM), and malignant (MAL) categories to establish better communication between pathologists and clinicians.

This study aimed to reclassify the serous body fluids according to TIS and assess their risk of malignancy (ROM).

A retrospective cross-sectional study was conducted in the Department of Pathology for a period of 4.5 years after obtaining clearance from the Institutional Ethics Committee. Serous effusions, having corresponding cell block or tissue biopsy, were recategorized as per the TIS, and ROM was calculated for all categories. Continuous variables were represented as ranges, medians, and means. Analysis of variance (ANOVA) and chi-square tests were used to analyze the distribution of continuous variables as per the TIS category.

This study included 370 fluids. The majority (224 samples, 60.5%) comprised ascitic fluid, followed by 136 pleural fluids (36.7%). ND, NFM, AUS, SFM, and MAL categories had 7 (1.89%) cases, 285 (77%) cases, 6 (1.62%) cases, 15 (4.05%) cases, and 57 (15.4%) cases with ROM of 14.28%, 10.82%, 83.33%, 86.66%, and 100.00%, respectively. ANOVA and chi-square tests showed a P value of 0.002.

TIS is a standardized and efficient approach in categorizing serous body fluids. Due to the close ROM observed in the AUS and SFM categories, there lies a scope for finer refinement of the criteria for the AUS category.