Clinicopathologic Features of Noninvasive Inverted Urothelial Papillary Tumor

Clinicopathologic features and recurrence rates of inverted noninvasive urothelial papillary tumors have been poorly characterized to date with few larger studies evaluating long-term outcomes. The spectrum of histomorphology, clinical features, and prognosis of inverted lesions of the urinary bladder are retrospectively reviewed.Archived paraffin-embedded urothelial tumor samples from patients diagnosed with inverted urothelial papillary lesions between January 2005 and June 2020 were collated. A matched control population of patients with exophytic papillary lesions of the urothelium diagnosed during the same time period was randomly selected. The conventional clinicopathologic features of inverted urothelial papillary tumor were evaluated retrospectively and patient demographics, tumor characteristics, recurrence, and survival information were recorded.Lower recurrence rates were observed for inverted papillary urothelial neoplasm of low malignant potential (IPUNLMP) relative to papillary urothelial neoplasms of low malignant potential and for low-grade papillary urothelial carcinoma with an inverted growth pattern (LG-PUCI) relative to low-grade papillary urothelial carcinomas. No recurrence was found among the inverted urothelial papilloma cases. The 2- and 5-year disease-free survival rates were 100.0% and 85.2% for IPUNLMP patients; 94.4% and 80.4% for papillary urothelial neoplasms of low malignant potential; 89.5% and 82.0% for LG-PUCI; 73.7% and 54.6% for low-grade papillary urothelial carcinoma; 40.0% and 20.0% for high-grade papillary urothelial carcinoma with an inverted growth pattern patients and 26.7% and 26.7% for high-grade papillary urothelial carcinoma. Multivariate Cox regression analysis of IPUNLMP and LG-PUCI/high-grade papillary urothelial carcinoma with an inverted growth pattern indicated that tumor number (hazard ratio=4.356; 95% CI: 1.145-16.570; P =0.031) was a powerful prognostic factor for disease-free survival.Noninvasive, papillary urothelial lesions of the bladder tend to have lower recurrence and a better outcome if an inverted growth pattern is shown.