CD274 and head and neck squamous cell carcinoma: Initially developed to identify NSCLC patients most likely to benefit from anti-PD-1/PD-L1 therapies [9], it is nowadays used as a companion diagnostic for several other cancers, including urothelial carcinoma [10], head and neck squamous cell carcinoma (HNSCC) [11], triple-negative breast cancer (TNBC) [12], gastric and gastroesophageal junction cancers [13], and cervical cancer [14].