CD274 and head and neck squamous cell carcinoma: The aims of this study were to explore a potential role of CDK19 in HNSCC progression and aggressiveness and to characterize a potential implication of CDK19 on a STAT1/PD-L1 signaling axis in HNSCC, using immunohistochemistry (IHC) staining on formalin-fixed paraffin-embedded (FFPE) tissue samples of a well-characterized HNSCC cohort.