Yanagawa N, Shiono S, Endo M, et al. - Researchers here examined patients with surgically resected non-small cell lung carcinoma for programmed death ligand 1 (PD-L1) immunohistochemical expression and its correlation with clinicopathological and molecular characteristics in these patients. Among 633 patients with adenocarcinoma, PD-L1 expression was not identified in 523 (82.6%), low expression was seen in 78 (12.3%) and high expression in 32 (5.1%). Males, smokers, patients with a more advanced stage, the solid predominant subtype, no EGFR mutations, a high MIB-1 labeling index and positive p53 immunohistochemical expression more commonly had PD-L1 expression. In multivariate logistic regression analysis, PD-L1 expression was noted in significant and independent correlation with the solid predominant subtype, no EGFR mutations, a high MIB-1 labeling index and p53 positivity. Positive expression of PD-L1 was noted in strong association with the combination of the solid predominant subtype with a high MIB-1 labeling index. Among 193 patients with squamous cell carcinoma, PD-L1 expression was not seen in 92 (47.7%), low expression was noted in 57 (29.5%) and high expression in 44 (22.8%). PD-L1 expression seemed to have no significant correlations with the evaluated clinicopathological or molecular characteristics of these patients. Overall findings suggest correlation of PD-L1 with various clinicopathological or molecular characteristics in adenocarcinoma but not squamous cell carcinoma; these findings may aid in selection of patients with a good response to immune checkpoint inhibitors.