PIK3CA and head and neck cancer: Combined with our previous studies that high incidence of PIK3CA gene mutations was identified in the other tumor types of human head and neck squamous cell carcinomas such as pharyngeal cancer [14, 15], the current study further confirmed the importance of oncogenic PIK3CA in the carcinogenesis of salivary duct epithelial cells and highlighted a critical oncogenic PI3 K signaling pathway in human head and neck cancers.