In patients with NSCLC, the mean value of CAIX in plasma was 45.40 pg/ml (range: 0–372.89 pg ml−1) and was significantly higher than in healthy individuals (mean=2.48 pg ml−1, range: 0–16.65 pg ml−1) (P<0.001) (Figure 2A). Here, CA9 is linked to non-small cell lung carcinoma.