PIK3CA and head and neck squamous cell carcinoma: Interestingly, both cervical squamous cell carcinoma (CESC) and HPV positive HNSCC show an increase rate of PIK3CA mutations in comparison to other solid tumors, and the PIK3CA-AKT-mTOR pathway is the most frequent dysregulated signaling pathway in HNSCC, including >80% of all HPV negative and HPV positive cases [4, 5].