CD8A and esophageal squamous cell carcinoma: In order to investigate the contexture and possible clinicopathological implications of the IM including the PD-1 / PD-L1 axis in ESCC, we immunohistochemically analyzed the extent and distribution of overall and intraepithelial CD3+ / CD8+ TILs as well as PD-1 / PD-L1 expression in a tumor series of 125 primary resected, therapy-naive ESCCs.