Prognostic significance of subclassifying stage pT3a renal tumors with fat invasion: a retrospective study of 99 patients

PURPOSE: To analyze the recurrence in patients with clinic stage T1 renal cell carcinoma (RCC) who were upstaged to stage T3a after partial nephrectomy (PN) using a new sub-classification criterion. METHODS: A retrospective study of pathological characteristics was performed in patients who were upstaged to pT3a on the basis of fat invasion (FI). RESULTS: After analyzing the pathological findings, we proposed the following new sub-classification criteria for pT3a RCC with FI: (1) renal tumor invades the pseudo-capsule and contacts the perinephric adipose tissue directly or the tumor protrudes into the perinephric adipose tissue like a tongue (Type A); and (2) tumor nodules are distributed in perinephric adipose tissues (Type B). A significant difference was observed in the recurrence rate between the two subtypes A and B. For Type B, the recurrence rate after radical nephrectomy (RN) and PN was 15.79% and 63.64%, respectively. The recurrence rates for Types A and B after PN were 11.11% and 63.64%, respectively. CONCLUSIONS: T3a RCC with tumor nodules in perinephric adipose and/or an irregular tumor protruding into the adipose tissues lead to a higher recurrence rate. We recommend that T3a RCC be carefully analyzed and patients be treated on an individual basis.