Age, tumor size, cirrhosis, and antiviral therapy were significantly associated with p21 expression (χ2=5.722, P=0.017; χ2=4.358, P=0.037; χ2=9.576, P=0.002; χ2=12.564, P<0.001; respectively, Table 1). The gene discussed is CDKN1A; the disease is neoplasm.