CD274 and human papilloma virus infection: The results indicated that high PD-L1 expression was correlated with sex (RR = 1.28, 95% CI: 1.16–1.42, P < 0.001), N stage (RR = 1.19, 95% CI: 1.06–1.33, P = 0.003), M stage (RR = 1.64, 95% CI: 1.01–2.66, P = 0.044), low differentiation (RR = 1.16, 95% CI: 1.01–1.33, P = 0.034), and human papilloma virus infection (RR = 1.38, 95% CI: 1.14–1.68, P = 0.001), but unrelated to TNM stage or T stage.