CA9 (Carbonic anhydrase 9) and NDUFA4L2, a NADH dehydrogenase subunit, are strong candidate biomarkers for ccRCC metastasis [58,59,60]; moreover, NDUFA4L2 overexpression contributes to increase the drug resistance of ccRCC cells [61]. Here, CA9 is linked to nonpapillary renal cell carcinoma.