This meta-analysis also showed that low CAIX expression was significantly correlated with worse RCC grade (OR = 0.41, 95% CI = 0.31–0.54, P<0.00001, Figure 7) and depth of invasion (OR = 0.50, 95% CI = 0.24–1.02, P = 0.06, Figure 8). This evidence concerns the gene CA9 and renal cell carcinoma.