High‐Grade Urothelial Carcinoma Arising From a Ureteral Diverticulum: A Rare Case Report

Introduction: Ureteral diverticula are rare urological anomalies characterized by outpouchings of the ureteral wall. Malignancy arising from these structures is exceptionally rare, with only a few cases reported. Case Presentation: We report a 57-year-old male with high-grade urothelial carcinoma arising from a ureteral diverticulum in the left distal ureter. The patient experienced painless gross hematuria, and computed tomography revealed a 3 cm undetermined mass near the left distal ureter. Multiple endoscopic diagnostic procedures were inconclusive, with the final diagnosis confirmed intraoperatively. The surgery involved resection of the mass, and intraoperative frozen section analysis revealed high-grade urothelial carcinoma. A segmental ureteral resection was performed with reconstruction using a Boari flap and Psoas hitch. Final histopathology confirmed locally advanced, high-grade pT3 urothelial carcinoma, and adjuvant chemotherapy was recommended. Conclusion: This case underscores the diagnostic and management challenges of upper tract urothelial carcinoma, especially in rare cases involving ureteral diverticula.