Fig. 1

Representative immunohistochemical images of PD-L1 expression in esophageal squamous cell carcinoma. PD-L1 expression was scored from 0 (a), 1+ (b), 2+ (c), to 3+ (d). Cases with scores of 0 were considered PD-L1-negative, while cases with scores ≥1+ were considered positive for PD-L1 expression. (e) Electropherograms of the mutated sequences in exon 9 of PIK3CA gene. (Original magnification, × 200)