Lung adenocarcinoma is the most common histology type of lung cancer clinically in many countries.A new international multidisciplinary classification was proposed by International Association for the Study of Lung Cancer/American Thoracic Society/ European Respiratory Society(ISALC/ATS/ERS) in 2011,renewing the classification of lung adenocarcinoma in detail,in which invasive adenocarcinoma were further classified as lepidic-predominant,acinar predominant,papillary predominant,micropapillary predominant and solid predominant according to growth patterns.In 2015,World Health Organization introduced the concept of "air space invasion".As an important constituent part of air space invasion,spreading through air spaces(STAS) often occurs in lung cancer,especially early-stage lung adenocarcinoma.STAS is defined as the "spread of lung cancer cells into air spaces in the lung parenchyma beyond the edge of the main tumor".STAS is not only an independent prognostic factor besides growth patterns,but also an independent risk factor of local and distant relapse after limited resection of stageⅠlung adenocarcinoma.Therefore,it is of great guiding significance to judge the existence of STAS either preoperatively or intraoperatively in order to choose a suitable operation method and postoperative treatment of lung adenocarcinoma.This review mainly focuses on the latest research progress on the pathological appearance,related factors,mechanisms and clinical significance of STAS.