The Paris System for reporting urinary cytology in the follow-up of non-muscle-invasive bladder cancer

Introduction This study aimed to investigate the correlation between the Paris System for Reporting Urinary Cytology (TPS) and cystoscopic findings in histologically confirmed bladder cancer recurrences. We also assessed patient-specific variability in urinary cytology findings during the bladder cancer follow-up. Materials and methods This retrospective, single-center study included 180 patients with non-muscle-invasive bladder cancer (NMIBC) who were treated at Kuopio University Hospital between January 2014 and December 2021. A total of 968 follow-up urinary specimens were correlated with cystoscopy results. Of the 336 histological samples obtained during follow-up, 271 were paired with the cytology results. Results Patients with high-grade urothelial carcinoma (HGUC) cytology showed a high cumulative risk of progression to muscle-invasive disease. Recurrence risk increased with higher cytological class, whereas negative for high-grade urothelial carcinoma (NHGUC) and atypical urothelial cells (AUC) showed consistently low and comparable recurrence rates. When stratified by the highest cytological category during follow-up, biopsies of red patches at cancer recurrence revealed neoplasia rates of 3.6%, 4.8%, 40.0%, and 100% for NHGUC, AUC, suspicious for high-grade urothelial carcinoma (SHGUC), and HGUC, respectively. Conclusion This study suggests that urinary cytology using TPS is useful for assessing the risk of malignancy when no exophytic tumor is observed on cystoscopy. The risk of high-grade recurrence or progression was low when cytology was classified as NHGUC or AUC. In the absence of visible tumors, surveillance without biopsy may be a safe option if cytology is NHGUC or AUC. Micro-abstract The role of urinary cytology in guiding the biopsy of non-exophytic bladder lesions remains unclear. We retrospectively analyzed 968 follow-up cytology specimens from 180 patients with NMIBC using the Paris System. NHGUC and AUC were associated with low recurrence and progression risk, supporting the conservative management of non-exophytic lesions in selected patients.