Purpose: In 2002 the American Joint Committee on Cancer revised the TNM staging system, introducing subclassification for T1 tumors, and invasion of renal sinus fat and sinus veins in categories T3a and T3b, respectively. Since renal sinus invasion represents the most common site of extrarenal extension, the relationship between size, and renal sinus invasion and its effect on the T classification was examined in prospective fashion.
Materials and methods: A total of 175 renal cell carcinomas were examined in prospective fashion with careful evaluation for renal sinus invasion. A minimum of 5 blocks of the renal sinus-tumor interface were examined. Tumors were staged using the 2002 TNM formulation.
Results: The distribution of tumors types was clear cell renal cell carcinoma (CC) in 120 cases, papillary renal cell carcinoma in 30, chromophobe renal cell carcinoma in 12 and miscellaneous other carcinomas in 13. T classifications correlated with tumor type. Only 3 of 30 papillary renal cell carcinomas (10%) and 2 of 9 chromophobe renal cell carcinomas (16.6%) demonstrated extrarenal extension compared with 59 of 120 CCs (49%) (p <0.01). Renal sinus invasion occurred more often than capsule invasion (49% vs 20%, p <0.01). No tumor invaded the capsule that did not also invade the sinus. Compared with 1.1 to 4 cm CCs, of which 85% were renal limited, only 32% of CCs that were 4.1 to 7 cm (p <0.01) and 3% of those larger than 7 cm were renal limited, that is T1b and T2, respectively.
Conclusions: The incidence of renal sinus invasion increases sharply after tumors exceed 4 cm. T1b CC is uncommon and T2 CC is rare if careful evaluation for sinus invasion is performed.