Figure 1. Programmed death- ligand 1 (PD-L1) expression in lung squamous cell carcinoma. (a) Representative PD-L1 staining images. The tumor cell membrane is stained. 0: negative, 1: weak, 2: moderate, and 3: strong. (b) A histogram of the H score distribution. The cut-off value of 100 was chosen because of the bimodal distribution. (c) A Kaplan-Meier plot of recurrence-free survival after surgery. The PD-L1 high and PD-L1 low groups are shown by the black and red lines, respectively. The p values were calculated by a log-rank test.