PIK3CA and head and neck squamous cell carcinoma: Mutations in genes such as PIK3CA, PTEN, DDX3X, FGFR2/3 and BRCA1/2, TRAF3/CYLD genes, and enriched copy number variations in PIK3CA, KRAS, MLL2/3, NOTCH1, and DNA repair genes were also reported in HPV-positive HNSCC (Chung et al., 2015; Seiwert et al., 2015; Hajek et al., 2017).