PIK3CA and head and neck squamous cell carcinoma: Another amplification region 3q26.33 harbored important caner-causing genes such as PIK3CA, SOX2, FGF12 and TP63. Alterations of PIK3CA which leads to dysfunction of cell cycle control, was also frequently found in colorectal cancer, HNSCC, gastric cancer and breast cancer (Mei et al., 2016; DeMello et al., 2018; Azizi Tabesh et al., 2017; Du et al., 2017).