PDCD1 and head and neck squamous cell carcinoma: Patients with tumour cells with simultaneous high levels of PD-1 in TILs and PD-L1 may have shorter disease-free survival than patients with single expression of either marker.71 These data highlight that PD-1/PD-L1 overexpression in cancer could have adverse outcomes.72 The microenvironment of HNSCC requires further exploration and understanding using a multiparametric approach.