MMP9 and hepatocellular carcinoma: In addition, one study of four genes [E‐cadherin, MMP9 (matrix metalloproteinase‐9), TCF3 (transcription factor 3)/E47 and ID2 (inhibitor of differentiation 2)] has validated their prognostic value, in terms of overall survival, in a large cohort of hepatocellular carcinomas (HCC) (Kim et al., 2010).