CA9 and nonpapillary renal cell carcinoma: Even among the plethora of investigated molecular markers, specific to ccRCC biology (CAIX, VEGF, HIF), proliferation/cell cycle (Ki67, p53, p21 [215], PTEN [216]), cellular adhesion (E-cadherin, CD44 [217,218]), immune response (osteopontin [219], CXCR4 [220], PD-L1 [221]), and epigenetic modifications (miRNA, gene methylations), none could produce more than level III evidence [222].