High PD-L1 expression, using FDA-approved immunohistochemistry companion diagnostic tests (e.g., 22C3 pharmDx on Dako Omnis, Agilent, for pembrolizumab, MSD; or SP263 on Ventana for atezolizumab, Roche), is currently the most robust predictive biomarker of response to anti-PD-(L)1 agents, and is routinely used in patients with advanced NSCLC, bladder cancer, and head and neck squamous cell carcinoma [59,88,89,90,91,92]. The gene discussed is CD274; the disease is head and neck squamous cell carcinoma.