Comparable categorical distribution of programmed death ligand 1 (PD-L1) expression. (A) Within all 564 clinical cases. (B) In adenocarcinomas. (C) In squamous cell carcinomas. Inadequate cases were defined as those which had insufficient tumor content (<100 malignant cells) available for analysis. (D, E) Left-to-right display representative images of (i) hematoxylin and eosin staining (H&E), (ii) negative PD-L1 expression, (iii) 1% to 49% PD-L1 expression, and (iv) more than 50% positive PD-L1 expression for adenocarcinoma and squamous cells carcinoma, respectively.