Urothelial (Transitional Cell) Carcinoma
Urothelial carcinoma (also known as transitional cell carcinoma) is the cancer type that presents in the renal pelvis. 1
Anatomic Distribution
Approximately 8% of all urothelial tumors originate in the renal pelvis, while the vast majority (>90%) arise in the bladder, and the remaining 2% occur in the ureter and urethra. 1
Urothelial carcinoma can develop anywhere urothelium (transitional epithelium) is present throughout the urinary tract—from the renal pelvis through the ureter, bladder, and proximal two-thirds of the urethra. 1
When considering upper tract urothelial carcinoma (UTUC) specifically, pelvicalyceal location is twice as common as ureteral location, with approximately 15% of renal tumors being urothelial carcinoma. 1
Clinical Characteristics of Renal Pelvis Urothelial Carcinoma
Upper tract urothelial carcinomas (including renal pelvis) present at more advanced stages compared to bladder cancer, with approximately two-thirds being invasive at diagnosis versus only 15-30% for bladder tumors. 1
Multifocal disease occurs in 25-30% of UTUC cases at initial diagnosis. 1
The hallmark of urothelial carcinoma is multiplicity and recurrence: 2-4% of patients with bladder cancer develop upper tract UC, while 40% of patients with UTUC subsequently develop bladder cancer. 1
Hematuria is the presenting complaint in 75-95% of patients with UTUC. 1
Histologic Classification
Urothelial carcinomas are classified as low-grade or high-grade based on the extent of cytologic and architectural atypia. 1
Non-muscle-invasive tumors may have flat (including carcinoma in situ) and/or papillary histology. 1
Papillary lesions include papillary urothelial neoplasms of low malignant potential (PUNLMP) and papillary urothelial carcinoma (low- and high-grade). 1
Important Clinical Pitfall
The 2022 WHO Classification now uses "subtype" instead of "variant" to describe distinct morphologic categories within urothelial carcinoma, as "variant" is now reserved for genomic alterations. 1 This terminology change is critical for accurate pathology reporting and treatment planning, as histologic subtypes may define natural history, risk of progression, and need for more aggressive treatment approaches. 1