EGFR and head and neck squamous cell carcinoma: Such demonstrated functional similarities between MAPK1p.D321N mutation and MAPK1p.E322K (in the erlotinib exceptional responder6,7), in terms of driver activities, EGFR hyperactivating capabilities, and erlotinib sensitivities, do provide direct evidence for potential use of the EGFR inhibitor, erlotinib, for MAPK1p.D321N and p.E322K-mutated HNSCC in a precision manner.