With the continuous innovation of genomics,proteomics and molecular biological detection technol-ogy,the treatment of non-small cell lung cancer(NSCLC)has changed from traditional chemotherapy to immunotherapy and targeted therapy.Among them,molecular tumor markers targeting tyrosine kinase pathways play more important roles in clinical practice.For advanced NSCLC patients with positive epidermal growth factor receptor(EGFR)mutations,there are many first-line drugs on the market and they could bring significant efficacy,thus completely subverting the treatment pattern of advanced NSCLC.Common mutations of EGFR in Chinese patients are located on exons 19,20 and 21,of which exons 19 and 21 mutations are the more common types.Besides,there is also a subtype of EGFR mutations,known as EGFR 20 exon insertion(EGFR 20ins)mutation.The authors summarized the treatment of a lung adenocarcinoma patient with EGFR 20ins mutation accepting Furmonertinib mesylate,in order to provide effective references for clinical diagnosis and treatment.