PIK3CA and head and neck squamous cell carcinoma: Specifically for PI3K, the in-depth analysis of TCGA data from 428 HPV− and 76 HPV+ HNSCC samples [20] revealed that PIK3CA is the highest mutated gene when considering all HNSCC cases (16.8%), and PI3K mutations (PIK3CA, PIK3CB, PIK3CG, and PIK3CD) are frequently mutated genes in 30% of the HPV+ lesions.