CD274 and esophageal squamous cell carcinoma: The questions we addressed focused on (1) the specific composition of the IM in ESCC, (2) the identification of possible associations of overall and intraepithelial TILs with specific clinicopathological and survival parameters, (3) the predictive value of PD-L1 immunohistochemistry in ESCC and (4) the relationship of the PD-1 / PD-L1 axis to the IM, particularly focusing on potential immunologic ESCC subgroups based on their extent of T-cell infiltration and PD-L1 positivity.