To stage or not to stage: determining the true clinical significance of the biopsy tract through perinephric fat in assessing renal cell carcinoma

Aims Perinephric fat invasion (PFI) is a key component of renal cell carcinoma (RCC) staging, but there are limited data pertaining to biopsy tract seeding (BTS) resulting in perirenal tissue involvement [BTS with perinephric fat invasion (BTS‐P)].The aim is to correlate clinical outcomes with pathologic stage to determine whether the presence of BTS‐P should be considered a criterion to stage RCC as part of the pT3a category in the absence of any other upstaging variables. Materials and results We identified 304 renal biopsies from patients with subsequent nephrectomies for RCC; 33 of the tumours contained PFI. Each case was reviewed to determine the presence of BTS‐P and other forms of invasion [e.g. non‐BTS‐P PFI, sinus fat invasion (SFI), and/or renal vein invasion (RVI)], and these findings were compared with survival outcomes. Ten (30%) of 33 tumours with PFI showed BTS‐P as the only finding, and were otherwise pT1 tumours; six (60%) patients were alive without disease (AWOD) (mean, 77.5 months), three were lost to follow‐up (LTF), and one died of other disease (DOOD). Two patients showed true PFI plus BTS‐P; one was LTF and one is AWOD at 107 months. Ten (43%) of 23 patients with tumours with true invasion (PFI ± SFI and/or RVI) are AWOD (mean, 97.7 months), eight (35%) died of disease (DOD), four were LTF, and one DOOD. Kaplan–Meier survival curves showed that the cancer‐specific survival was significantly worse in patients with true invasion (P = 0.044) than in those with BTS‐P as the sole finding. Conclusion Patients with tumours showing BTS‐P only appear to have better outcomes than those with other non‐PFI invasion, suggesting that this finding should not be upstaged to pT3a. Additional studies are needed to corroborate the significance of our observations.