CD274 and head and neck squamous cell carcinoma: We retrospectively analyzed 129 treatment-naïve head and neck squamous cell carcinomas (HNSCCs) for the expression of programmed death ligand 1 (PD-L1), CKLF-like MARVEL transmembrane domain-containing 6 (CMTM6), tumor-infiltrating leukocytes (TILs), and tumor-associated macrophages (TAMs).