CA9 and neoplasm: Forty percent of TNBCs were observed to express CAIX protein and demonstrated significant association with larger tumour size (P = 0.002), higher histological grade (P < 0.001), and significantly worse disease-free survival (DFS) and overall survival (OS) (after adjustment: HR = 2.99, 95% CI = 1.78–5.02, P < 0.001 and HR = 2.56, 95% CI = 1.41–4.65, P = 0.002, respectively).