Application of The Paris System in neobladder washing cytology: Comparison between the original diagnosis and correlation with histopathology

Background: In urinary diversion after radical cystectomy, the incidence of recurrent urothelial carcinoma (UC) in upper urinary tract or urethra are reported in 2%-17% of the patients. Urine cytology plays a pivotal role in detecting the recurrence of UC. However, cytologic diagnosis in urinary diversion including neobladder is often challenging due to significant degenerative changes and necro-inflammatory background. Since the proposal of The Paris System (TPS) for reporting cytology, the utility of TPS in urinary diversion specimen has not been studied yet. The objective of this study is to evaluate the diagnostic usefulness of TPS compared with the original diagnosis and correlate with the matched histopathological results.Methods: Urinary diversion cytology specimens with concurrent or subsequent biopsy or resection at EUMC in recent 16 years (from January 2002 to December 2018) are retrospectively reviewed and reclassified according to TPS criteria. The TPS categories and the original diagnoses were compared and correlated with follow-up histology.Results: Concurrent or subsequent biopsy or resection within a 6-month period was available in 45 cases from 28 patients. When applying TPS, the rate of atypical and suspicious categories decreased by 13.4% and 11.1%. Using TPS increased the value of sensitivity, NPV, and accuracy to 93.75%, 93.75%, and 90.91%, respectively.Conclusion: Application of TPS reduced the rate of indeterminate diagnoses and moreover, improved the sensitivity and accuracy of urinary diversion cytology. Therefore, we believe that diversion urine cytology diagnosis according to TPS is useful to screen patients for detection of recurrence in routine clinical practice.