CD274 and neoplasm: A multivariate analysis (to identify factors that affect PD-L1 expression) revealed that only WHO classification was a significant determining factor of PD-L1 expression among age (p = 0.41), sex (p = 0.92), smoking habit (p = 0.67), WHO classification (p = 0.01), tumor size (p = 0.41), stage (p = 0.30), and formalin fixation method (p = 0.43).