Mutations of epidermal growth factor receptor 1 (EGFR) gene occur in about 15 % of all NSCLCs in Western Europe and are frequently located in exons 19 and 21, being associated with high sensitivity to EGFR tyrosine kinase inhibitors (TKIs). By contrast, exon 20 insertions account for up to 10 % of all EGFR mutations and are correlated to EGFR TKI resistance. Herein, we describe a novel mutation in EGFR exon 20 in a female non-smoker bearing a lung adenocarcinoma, characterized by the insertion of a nucleotide triplet GTT, which translates into a protein with an additional Valine between Proline 772 and Histidine 773 (p.P772_H773insV-c.2316_2317insGTT). The patient was treated with cisplatin/pemetrexed 1st-line and docetaxel 2nd-line chemotherapies, reporting a prolonged disease stabilization of 25 months. The identification and the biological and clinical characterization of novel EGFR mutations represent a prerequisite for their wide use as predictive biomarkers for personalized therapy in NSCLC.