Although the expression of PD-L1 is a main predictor, it must be balanced with other markers, such as the density, composition and activation state of inflammatory cells in the tumour microenvironment.66 The combination of the expression of PD-L1 in HNSCC tumour cells and the presence of CTLs is more predictive of tumour cell response than single expression in tumour cells.67 The gene discussed is CD274; the disease is head and neck squamous cell carcinoma.