CD274 and head and neck squamous cell carcinoma: Blockade of the PD-1 or PD-L1 pathway has been shown to exert therapeutic activity in patients with Hodgkin lymphoma [39], head and neck squamous cell carcinoma [40], advanced melanoma [41, 42], non-small cell lung carcinoma [43, 44], and renal cell carcinoma [45, 46].