Renal cell carcinoma invading the urinary collecting system: implications for staging.

PURPOSE: Current TNM staging of renal cell carcinoma is based on the tumor propensity for local extension (T), nodal involvement (N) and metastatic spread (M). Locally advanced renal cell carcinoma may involve the perirenal fat, adrenal glands, renal vein, vena cava and/or urinary collecting system. The existing TNM classification does not reflect the ability of renal cell carcinoma to invade the urothelium. We evaluated the incidence and characteristics as well as overall and cancer specific survival of renal cell carcinoma invading the urinary collecting system.

METHODS AND MATERIALS: We reviewed pathological findings in 504 kidneys from 475 patients with renal cell carcinoma who presented to our institution in a 3-year period. Urothelial involvement required evidence of gross or histological invasion of the renal calices, infundibulum, pelvis or ureter. Demographic and survival data were obtained from medical records and an institutional cancer registry for tumors invading the urothelium. Stage specific survival data were then compared with tumors not involving the urinary collecting system.

RESULTS: Definitive urothelial involvement by the primary tumor was interpretable in 426 of 504 kidneys. Invasion of the collecting system was identified in 61 of 426 cases (14%). Mean diameter of the invading lesions was 10.2 cm. (range 3 to 26). The majority of cases showed clear cell and sarcomatoid histology. Invasion by a papillary lesion was rare. Involvement of the collecting system was most common at the renal poles. Of 61 lesions invading the collecting system 48 (79%) were stage pT3 or greater, while only 13 (21%) were pathologically localized stage pT2 or less. Vascular invasion was identified in 38 renal cell carcinoma cases (62%) with urothelial involvement. A total of 16 cases (26%) were associated with vena caval thrombus. Invading tumors were high Fuhrman grade III or IV in 43 cases (70%). Overall disease specific survival was poor with a median of 19 months. In patients with localized stage pT1 or pT2N0M0 disease and urothelial invasion median disease specific survival was 46 months.

CONCLUSIONS: Renal cell carcinoma lesions involving the renal collecting system are characteristically large, high grade and high stage. Clear cell carcinoma most commonly invades, while invasion by papillary tumors is rare. Overall the prognosis for high stage lesions with urothelial involvement is poor and does not appear significantly different from the reported disease specific survival of patients with high stage lesions without urothelial invasion. Localized tumors 4 cm. or less, which are amenable to elective nephron sparing surgery, rarely invade the urothelium. However, when a low stage pT2 or less renal lesion involves the urinary space, survival appears worse than equivalently staged renal cell carcinoma without invasion. Including urothelial invasion into current TNM staging systems for renal cell carcinoma is unlikely to provide significant additional prognostic or therapeutic information.