Reappraisal of T3N0/NxM0 renal cell carcinoma: significance of extent of fat invasion, renal vein invasion, and adrenal invasion.

T3 renal cell carcinoma (RCC) is a heterogeneous group of tumors that are substaged based on perirenal or sinus fat invasion, adrenal invasion, and renal vein invasion. To evaluate whether the extent of fat invasion (minimal versus extensive) and direct adrenal gland invasion, renal vein invasion with or without concurrent fat invasion has a similar prognosis, we retrospectively reviewed 198 T3N0/NxM0 RCCs in a single academic tertiary hospital. Fat invasion was subdivided as minimal (< or =5 mm into the fat) or extensive (>5 mm) invasion. Direct adrenal invasion was defined as contiguous involvement of ipsilateral adrenal gland. Among the 198 T3 RCCs, minimal and extensive fat invasions were identified in 57 and 61 cases, respectively; renal vein invasion and direct adrenal invasion were seen in 66 and 14 cases. The patients' average age was 62.9 years, and 145 patients were male and 53 were females. The 2-year and 5-year survival rates were 85% and 56% for minimal fat invasion, 76% and 70% for extensive fat invasion, and 55% and 32% for renal vein invasion, respectively. There was no difference of survival in patients with T3b (renal vein invasion) RCC stratified by presence or absence of concurrent fat invasion. The 2-year and 5-year survival rates for adrenal invasion were 31% and 21%, respectively, which was significantly worse than that of fat or renal vein invasion. Multivariate analysis showed that nuclear grade, sarcomatoid differentiation, and subgrouping of pT3 RCC (fat invasion, renal vein invasion, and adrenal invasion) remained independent predictors of patient's overall survival. In conclusion, our study shows that T3 RCCs with minimal or extensive perinephric fat invasion has a similar prognosis and is significantly more favorable than that of renal vein invasion regardless of presence or absence of concurrent fat invasion. In contrast, tumors with adrenal gland invasion carry a far worse prognosis than perinephric fat or renal vein invasion and thus supporting a separate stage category.