TP53 and head and neck squamous cell carcinoma: Our aim was to study the immunohistochemical (IHC) staining patterns of p53 in head and neck squamous cell carcinomas (HNSCC), and to compare p53 IHC staining patterns to TP53 mutation status as well as to p16 IHC staining and assess the ability of this two marker IHC panel to consistently and accurately subclassify HNSCC.