EGFR and head and neck squamous cell carcinoma: EGFR mutations drive tumorigenesis through the MAPK and PI3K signaling pathways for many cancers, including lung adenocarcinoma (LUAD), glioblastoma multiforme (GBM), colorectal adenocarcinoma (CRAD), and head and neck squamous cell carcinoma (HNSCC) [3,4,5].