Seiwert et al. proposed measuring, together with the expression of PD-L1, the levels of IFN-γ in HNSCC, as they directly influence the expression of PD-L1, and, likewise, to ensure that PD-L1 expression is related to T cell activity and not inflammation of the tumor microenvironment [169]. Here, IFNG is linked to head and neck squamous cell carcinoma.