PIK3CA and head and neck squamous cell carcinoma: Due to the increasing understanding of the molecular mechanisms and basic pathways in the pathogenesis of HNSCC, current research is focused on molecularly-targeted therapies specific for the pathways involved in the carcinogenesis of HNSCC, such as the epidermal growth factor receptor (EGFR) and phosphatidylinositol 3-kinase (PI3K) pathways.