In HPV-positive head and neck and cervical squamous cancers, mutations in PIK3CA are almost exclusively found in E542K (c.1624G > A) and E545K (1633G > A) corresponding to a C to T single base change at a TCW motif, indicative of APOBEC-induced mutagenesis [35,53,102,103,104,105]. This evidence concerns the gene PIK3CA and cervical squamous cell carcinoma.