PIK3CA and head and neck squamous cell carcinoma: Epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase that activates intracellular signaling pathways, including the phosphatidylinositol 3-kinase (PI3K)/AKT pathway (survival signal) and the ERK pathway (proliferation signal), and is abundantly expressed in the majority of epithelial malignancies, including head and neck squamous cell carcinoma (HNSCC) [1].