Subsequently, based on the classical ccRCC marker genes [22], we found that clusters 0, 1, 2, 5, 7, 8, 9, 11 and 12 had significantly elevated levels of carbonic anhydrase 9 (CA9) and NADH dehydrogenase (ubiquinone) 1 alpha subcomplex, 4-like 2 (NDUFA4L2) gene expression (Fig. 2C–E). The gene discussed is CA9; the disease is nonpapillary renal cell carcinoma.