Lung Adenocarcinoma in Never Smokers: Problems of Primary Prevention from Aspects of Susceptible Genes and Carcinogens.

Global statistics estimate that approximately 25% of patients with lung cancer are never smokers. We suggest that genes related to susceptibility to metabolic syndrome were present among those related to susceptibility to lung adenocarcinoma (AC) in never smokers. There are many questions concerning lung AC in never smokers, which is increasing in incidence, with female predominance, good prognosis, unique genes related to susceptibility and good response to treatment with specific agents. The purpose of this review was to investigate the carcinogenesis of lung AC in never smokers focusing on genes related to susceptibility to lung AC and carcinogens, including environmental factors. In order to clarify the carcinogenesis of lung AC in never smokers, the definition of never smokers, survey of environmental tobacco smoke, the presence of the physical characteristics of metabolic syndrome, and other carcinogens should be investigated for primary prevention of lung AC.