The patient was a 61-year-old Chinese man without a history of smoking or family history of lung cancer. He had been receiving systemic treatment for coronary heart disease for 13 years….The T790I (c.2369_2370delinsTA) mutation, a rare variant which causes a threonine (T) to isoleucine (I) missense mutation at codon 790, was identified...The patient was started on osimertinib (80 mg once daily) treatment in March 2019 with good tolerance and treatment for 16 months...Up to the date of this report, the patient is still receiving osimitinib treatment, and his condition is stable without significant progress.