AKR1C4 and nonpapillary renal cell carcinoma: Hierarchical clustering analysis revealed five main patient populations with one cluster of patients expressing low levels of these enzymes and four clusters mainly defined by the strong expression of each individual gene, demonstrating that HSD11B1, CYP21A2, AKR1C4 and HSD11B2 were mutually exclusively expressed in ccRCC patients (Figure 1c).