CAIX is also the main tumor-associated antigen overexpressed in ccRCC due to the frequent mutation of the tumor suppressor gene von Hippel-Lindau found in about 75% of ccRCC cases [12], which promotes hypoxia-independent expression of the HIF-1α-regulated genes, including CAIX [13,14]. Here, CA9 is linked to nonpapillary renal cell carcinoma.