The Paris system for reporting urinary cytology: what worked and what still needs to be improved

Abstract

Urine cytology has long been a challenging diagnostic modality due to its low sensitivity for low-grade urothelial neoplasms and high interobserver variability. The introduction of The Paris System (TPS) in 2016 marked a pivotal shift towards standardisation, with a primary focus on detecting high-grade urothelial carcinoma (HGUC). This review evaluates the impact of TPS on diagnostic accuracy, reproducibility, and clinical utility. It also highlights the system's limitations, including issues with nuclear-to-cytoplasmic (N/C) ratio estimation, cellular degeneration, and the underrepresentation of HGUC variants. The second edition of TPS (TPS 2.0) addresses many of these concerns, offering refined criteria and visual aids. However, further improvements are needed, particularly in the integration of molecular diagnostics and artificial intelligence.