In a comparative study performed on 108 tumor biopsy samples from stage I–IV HNSCC patients, results were assessed using 3 PD-L1 diagnostic assays: the Ventana SP263, the Dako 28–8, and Dako 22C3 assays, commonly used in durvalumab, nivolumab and pembrolizumab trials, respectively. The gene discussed is CD274; the disease is head and neck squamous cell carcinoma.