CD274 and esophageal squamous cell carcinoma: The number of CD8+ tumour-infiltrating immune cells (TIICs) and PD-1+ TIICs, and PD-L1 expression on tumour cells (PD-L1TC) were immunohistochemically examined in the surface (Surf), centre (Cent) and invasive front (Inv) of tumours surgically resected from 192 patients with ESCC.