CA9 and clear cell renal carcinoma: The subtypes that stain with CAIX are mainly the clear cell renal cell carcinoma (ccRCC), which is the most common subtype, about 70% of RCC [16], the clear-cell papillary renal cell carcinoma (ccpRCC), and sometimes, with often moderate intensity, the non-type 1 papillary renal cell carcinoma (pRCCII).