The clinicopathologic spectrum and prognostic features of bladder inverted papillary tumors: a cohort of 286 patients

To compare the clinicopathological features and identify prognostic factors for recurrence and progression in patients with low-grade inverted papillary urothelial tumors (IPUTs). This single-center retrospective study included 286 patients with primary low-grade IPUTs treated with transurethral resection between 2009 and 2017. The cohort comprised 120 inverted urothelial papilloma (IUP), 93 inverted papillary urothelial neoplasm of low malignant potential (IPUNLMP), and 73 low-grade inverted papillary urothelial carcinoma (LG-IPUC) cases. Clinicopathological features were compared, and recurrence-free survival (RFS) and progression-free survival (PFS) were analyzed using Kaplan–Meier methods and Cox regression. Compared with IUP/IPUNLMP, patients with LG-IPUC were older, had larger tumors (> 1.5 cm), more frequent multifocality, and a higher frequency of extra-trigonal tumor location (all P < 0.05). Recurrence rates were 0.8% (IUP), 6.5% (IPUNLMP), and 9.6% (LG-IPUC). Progression occurred in 3.2% (IPUNLMP) and 2.7% (LG-IPUC). In a multivariable analysis that should be considered exploratory given the limited number of recurrence events ( n = 14), tumor multiplicity (HR = 6.23, 95% CI: 2.06–18.85, P = 0.001) and location outside the bladder neck/trigone (HR = 10.92, 95% CI: 1.40–85.14, P = 0.022) were independently associated with recurrence. The wide confidence interval for tumor location indicates limited precision; these findings require validation. In an exploratory univariate analysis, tumor multiplicity was associated with progression (HR = 10.84, 95% CI: 1.811–64.885, P = 0.009); however, given only 5 progression events, this finding should be interpreted as hypothesis-generating rather than as evidence of an established predictor of progression. Tumor multiplicity and extra-trigonal location were stronger predictors of recurrence than histological subtype in the present low grade IPUTs cohort and model. These easily obtained clinical parameters may support practical risk stratification for postoperative surveillance. Progression analyses were exploratory, and the observed association with multifocality requires validation in larger cohorts.