CA9 and nonpapillary renal cell carcinoma: Plasma CAIX levels were significantly higher in ccRCC patients (p ≤ 0.005)CA IX activity was lower in healthy controls compared to ccRCC or BRT (kcat 5.57 × 104 s−1 vs. kcat 1.62 × 106 s−1 or 1.46 × 104 s−1)