To Stage or Not to Stage: Determining the True Clinical Significance of the Biopsy Tract Through Perinephric Fat in Assessing Renal Cell Carcinoma.

Perinephric fat invasion (PFI) is a key component of renal cell carcinoma (RCC) staging, but there is limited data pertaining to biopsy tract seeding (BTS), resulting in perirenal tissue involvement (BTS-P).

We identified 304 renal biopsies with subsequent nephrectomies for RCC of which 33 tumors 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 [SFI] and/or renal vein involvement [RVI]) and compared this to survival outcomes. Ten (30%) of 33 tumors with PFI showed BTS-P as the only finding and were otherwise pT1 tumors of which 6 (60%) patients were alive without disease (AWOD) (mean 77.5 months), 3 were lost to follow-up (LTF) and 1 died of other disease (DOOD). Two patients showed true PFI plus BTS-P, of which 1 was LTF and 1 is AWOD at 107 months. Ten (43%) of 23 patients with tumors with true invasion (PFI +/- SFI and/or RVI) are AWOD (mean 97.7 months), 8 (35%) died of disease (DOD), 4 were LTF and 1 DOOD. Kaplan-Meier survival curves revealed the cancer specific survival (CSS) is significantly worse in patients with true invasion (p=0.044) than in those with BTS-P as the sole finding.

Patients with tumors showing BTS-P alone appear to display better outcomes when compared to those with other non-PFI invasion, suggesting this finding should not be upstaged to pT3a. Additional studies are needed to corroborate the significance of our observations.

Histopathology. 2020 Nov 25 [Epub ahead of print]

Aida Valencia-Guerrero, Esther Oliva, Chin-Lee Wu, Shulin Wu, Travis Rice Stitt, Peter M Sadow, Douglas M Dahl, Adam S Feldman, Ronald S Arellano, Kristine M Cornejo

Department of Pathology, Massachusetts General Hospital, Boston, MA, USA., Harvard Medical School, Boston, MA, USA.