Using Percentage of Sarcomatoid Differentiation as a Prognostic Factor in Renal Cell Carcinoma.

The objective of this study was to determine if the percentage of sarcomatoid differentiation (%Sarc) in renal cell carcinoma (RCC) can be used for prognostic risk stratification, because sarcomatoid RCC (sRCC) is an aggressive variant of kidney cancer.We performed a retrospective analysis of patients who underwent surgery for RCC at our institution between 1999 and 2012. Pathology slides for all sRCC cases were reexamined by a single pathologist and %Sarc was calculated. %Sarc was analyzed as a continuous variable and as a categorical variable at cut points of 5%, 10%, and 25%. Potential prognostic factors associated with overall survival (OS) were determined using the Cox regression model. OS curves were generated using Kaplan-Meier methods and survival differences compared using the log-rank test.One thousand three hundred seven consecutive cases of RCC were identified, of which 59 patients had sRCC (4.5%). As a continuous variable %Sarc was inversely associated with OS (P = .023). Predictors of survival on multivariable analysis included pathologic (p) T status, tumor size, clinical (c) M status and %Sarc at the 25% level. OS was most dependent on the presence of metastatic disease (4 months vs. 21.2 months; P = .001). In cM0 patients with locally advanced (≥ pT3) tumors, OS was significantly diminished in patients with > 25 %Sarc (P = .045). However, %Sarc did not influence OS in patients with cM1 disease.Patients with sRCC have a poor overall outcome as evidenced by high rates of recurrence and death, indicating the need for more effective systemic therapies. In nonmetastatic patients, the incorporation of %Sarc in predictive nomograms might further improve risk stratification.