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Urinary cytology (UC) is one of the primary diagnostic modalities used for the screening and surveillance of urothelial carcinoma. Despite its widespread use, UC has suffered from a lack of standardized or reproducible criteria and wide interobserver variability, particularly of the designation of atypical urothelial cells. The Paris System for Reporting Urinary Cytology (TPS), published in 2016, aimed to provide a standardized approach for evaluating UC by creating diagnostic categories with specific cytomorphologic criteria. Recent studies have primarily investigated the application of TPS on lower urinary tract specimens and have mostly shown that TPS implementation has improved the performance of UC specimens. Only a few studies have reported the impact of TPS on upper urinary tract (UUT) cytology. Additionally, there is uncertainty as to which cytological features are most predictive of high‐grade urothelial carcinoma (HGUC) in the UUT. This review summarizes the literature regarding the utility and performance of UUT cytology and highlights findings before and after the implementation of TPS. Recent studies have investigated the application of The Paris System for Reporting Urinary Cytology (TPS) on lower urinary tract specimens and have mostly shown that TPS implementation improves performance. This review summarizes the literature regarding the utility and performance of upper urinary tract cytology specimens and highlights findings before and after the implementation of TPS. [ABSTRACT FROM AUTHOR]

Background: Urinary cytology is sensitive and specific for diagnosing and screening high‐grade urothelial carcinomas (HGUC). The Paris System (TPS) for urinary cytology was introduced in 2016 to standardize reporting. According to TPS diagnostic categories of HGUC and suspicious for HGUC (SHGUC), the average nuclear‐to‐cytoplasm (N:C) ratio of atypical cells should be ≥0.7. The objective of the current study was to measure the N:C ratio of urine cytology specimens with HGUC and SHGUC diagnoses and biopsy‐proven HGUC follow‐up. Methods: A cohort of 64 cases (HGUC, 49 cases; SHGUC, 15 cases) from 57 patients was constructed. Urine cytology slides were scanned into whole‐slide digital images. The nuclear and cytoplasmic areas were enumerated by digital image analysis (DIA), and the N:C ratios were measured. Results: In total, 640 cells were analyzed by DIA (HGUC, 490 cells; SHGUC, 150 cells). For HGUC and SHGUC, the average N:C ratios were 0.57 and 0.53, respectively. The maximum average N:C ratio was 0.73 for HGUC and 0.68 for SHGUC. HGUC had higher average N:C ratio (P <.001), higher average nuclear area (P <.001), higher average maximum N:C ratio (P =.005), and higher average maximum nuclear area (P =.006) compared with SHGUC. Conclusions: The N:C ratios for the HGUC (0.57) and SHGUC (0.53) categories are lower than those previously suggested in TPS. The authors advocate reducing the N:C ratio below the current threshold of 0.7.Digital image analysis demonstrates that the average nuclear‐to‐cytoplasmic ratio of malignant urothelial cells in urine specimens with diagnoses of high‐grade urothelial carcinoma (HGUC) and suspicious for HGUC (SHGUC) is below the 0.7 threshold set by The Paris System. The authors advocate for reducing the nuclear‐to‐cytoplasmic ratio for the HGUC and SHGUC categories in The Paris System. [ABSTRACT FROM AUTHOR]