A Case Report: High-Grade Urothelial Carcinoma in the Renal Pelvis with Complete Kidney and Ureter Duplication Featuring Heterologous Differentiation

This report describes a considerably rare case of high-grade urothelial carcinoma of the renal pelvis and ureter, presenting with heterologous differentiation, in a patient with bilateral duplicated kidneys. A 73-year-old male experienced intermittent gross hematuria for 5 months, accompanied by lower back and abdominal pain. Ultrasound and computed tomography scans revealed bilateral renal and ureteral duplication with multiple tumors in the left renal pelvis. A total nephroterectomy and bladder cuff resection were performed on the left two nephrons. Multiple space-occupying lesions were identified in the left renal pelvis and ureter. Histopathological examination showed poorly differentiated and diverse tumor cells, manifesting as sarcomatoid carcinoma, papillary adenocarcinoma, and infiltrating high-grade urothelial carcinoma. The tumor infiltrated the subcutaneous fibrous connective tissue of the renal pelvis and the full thickness of the ureter. Given the rarity of recurrent renal urothelial carcinoma with heterogeneous differentiation, comprehensive imaging and pathological assessments are vital to delineate the nature of the lesion and the direction of tissue pathological heterologous differentiation. These evaluations guide early radical surgical interventions, improving survival rates.