EGFR and head and neck squamous cell carcinoma: The constitutive activation of EGFR by gene mutations, gene amplification, or both, has been shown to be related to cancer initiation, progression, and poor prognosis in several cancers, including non-small cell lung cancer (NSCLC), colorectal cancer (CRC), squamous cell carcinoma of the head and neck (SCCHN), and glioblastoma [4,5].