CD274 and mouth disorder: The aim is to investigate the impacts of using multiplex immunochemistry (mIHC) staining to analyses the co-expression of programmed death ligand-1 (PD-L1) and tumor infiltrating lymphocytes (TILs) [CD8+ T cells and Forkhead Box Protein 3 (FOXP3)+ regulatory T cells (Tregs)] in different oral diseases, and oral squamous cell carcinoma (OSCC).