Invasive high-grade urothelial carcinoma of the bladder, renal pelvis, ureter, and prostatic urethra arising in a background of urothelial carcinoma with an inverted growth pattern: a contemporary clinicopathological analysis of 91 cases.

Urothelial carcinoma with an inverted/endophytic growth pattern can occasionally mimic inverted urothelial papilloma and pose diagnostic challenges when assessing the presence or absence of invasion. Making these distinctions is critical for guiding appropriate treatment and improving patient outcomes. Here we conducted one of the largest studies to date of invasive high-grade urothelial carcinoma arising in a background of urothelial carcinoma with an inverted growth pattern. Primary sites examined included bladder, renal pelvis, ureter, and prostatic urethra. Clinicopathological parameters including extent of invasion, variant histology, presence of urothelial carcinoma in situ, and clinical follow-up were obtained. Ninety-one cases from 82 patients were included in the study. Lamina propria invasion was present in 81% of bladder, 60% of ureter, 20% of renal pelvis, and 100% of prostatic urethra cases. Muscularis propria invasion was identified in 19% of bladder, 14% of ureter, and 20% of renal pelvis cases. Urothelial carcinoma invaded periureteric fat in 29% of ureter cases and invaded the renal parenchyma in 60% of renal pelvis cases. Clinical follow-up was available for 77 of 82 (94%) patients with a mean duration of 18 months. Recurrent urothelial carcinoma persisted in 63 of 82 (77%) patients, 16 of 82 (19%) progressed with metastatic disease, and 20 of 77 (26%) patients with bladder involvement died of disease. This study further emphasizes the importance of distinguishing these tumors from benign mimickers of urothelial carcinoma. Recognition of invasive foci is also critical in view of the potentially high frequency of recurrence and the possibility of advanced disease in a subset of these patients.