**Figure 3.** **Construction of cox regression model.** (**A**) The heatmap performed in R software on basis of risk score level and clinical characteristics (grade p=0.003). N stands for N classification in TNM system, and T stands for T classification in TNM system. (**B**) Survival analysis based on risk score. (**C**) The risk score distribution of differentiation grades. The y axis represent risk score level and x axis represent different grade (grade1 vs grade2, p=0.0002; grade1 vs grade3+4, p=0.0001). (**D**, **E**) Univariate cox regression and multivariate cox regression according to risk score and clinical characteristics. N stands for N classification in TNM system, and T stands for T classification in TNM system.