CD44 and nonpapillary renal cell carcinoma: Calculate the risk score of ccRCC patients according to the formula: risk score = (0.217 × CARS expression level) + (0.0098 × CD44 expression level) + (−0.0053 × DPP4 expression level) + (−0.307 × USP30-AS1 expression level) + (0.103 × GCLC expression level) + (−0.151 × HMGCR expression level) + (−0.0006 × HSPB1 expression level) + (−0.0094 × NCOA4 expression level) + (−0.0024 × SAT1 expression level) + (0.1523 × PHKG2 expression level) + (−0.007 × GOT1 expression level) + (−0.0024 × HMOX1 expression level).