CD274 and head and neck squamous cell carcinoma: To investigate the differences in TME of HNSCC with various PD-L1 expression, a retrospective analysis of 409 patients with HNSCC was performed to compare the immune signatures of tumors with high (CPS ≥ 20), moderate-low (CPS -1 to 19), or negative (CPS <1) PD-L1 expression.