Non-small cell lung cancer (NSCLC) accounts for roughly 85–90% of overall cases of lung malignancies and includes different histological subtypes. The treatment landscape of NSCLC has been terrifically changed by the discovery of Epidermal Growth Factor Receptor (EGFR) mutations and their response to the EGFR tyrosine kinase inhibitors (TKIs). EGFR gene aberrations have been defined as oncogenic driver mutations which occurred in 5–17% of lung adenocarcinomas among Caucasian patients, while in approximately 45–55% of the Asian population. Nowadays, EGFR-TKIs are the standard of care for patients affected by advanced EGFR-mutated NSCLC considering their established prolonged progression-free survival (PFS) in comparison to the standard chemotherapy approach. However, TKIs clinical efficacy remains restricted due to the development of resistance, which has been hardly clarified. The recent technological breakthrough and the advent of next-generation sequencing (NGS) platforms have enabled comprehensive profiling of the genome, providing novel evidence of co-existing multiple driver alterations.