CA9 and nonpapillary renal cell carcinoma: In accordance with the results of this method, the genes that were significantly associated with metastasis were—CA9, NDUFA4L2, BHLHE41, EGLN3, VWF, and IGFBP3. That is, the expression levels of these genes in metastatic and non-metastatic ccRCC tumors showed the property of linear separability.