Implementation of The Paris System for Reporting Urine Cytology improves diagnostic accuracy of selective upper urinary tract cytology.

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The Paris System for Reporting Urine Cytology (TPS) recommends diagnostic criteria for urinary tract cytology, focusing primarily on the detection of high-grade urothelial carcinoma (HGUC) in the lower urinary tract. The second edition of TPS (TPS 2.0), published in 2022, extends these recommendations to the upper urinary tract (UUT); however, there is a lack of comprehensive data on this subject. In total, 223 consecutive UUT cytology specimens from 137 patients were retrieved and reclassified according to TPS 2.0 criteria and were compared with the original diagnosis based on the conventional system (CS). Histologic follow-up within a 3-month period was conducted for 43 patients. Histologic follow-up revealed 30 HGUCs, five low-grade urothelial carcinomas (LGUCs), and eight nonneoplastic fibrotic tissues. The risk of high-grade malignancy for each TPS diagnostic category was 16.7% for nondiagnostic/unsatisfactory, 2.3% for negative for HGUC (NHGUC), 42.1% for atypical urothelial cells, 50.0% for suspicious for HGUC (SHGUC), and 81.8% for HGUC. In all five cases of histologically diagnosed LGUC, the cytologic diagnosis was NHGUC. When SHGUC/HGUC was considered positive, the diagnostic accuracy of TPS had 63% sensitivity, 95% specificity, a 90% negative predictive value, and a 79% positive predictive value, which were better than those of CS. In addition, the TPS indices did not differ significantly between the specimens obtained before and after the application of contrast reagents. TPS implementation improved the accuracy of UUT cytology in predicting histologic HGUC, which was unaffected by the application of contrast reagents. These data indicate the usefulness of TPS for UUT cytology in routine clinical settings.