BackgroundThe aim of this study was to investigate the relationship between predominant subtype, classification, and prognosis in Chinese stage I lung adenocarcinoma patients according to the International Association for the Study of Lung Cancer/American Thoracic Society/European Respiratory Society (IASLC/ATS/ERS) International Multidisciplinary Lung Adenocarcinoma Classification. MethodsBetween 2000 and 2010, 110 patients with stage I lung adenocarcinoma underwent surgery at Xuanwu Hospital. Two pathologists independently reclassified all resected specimens according to the IASLC/ATS/ERS classification. Survival curves were plotted using the Kaplan-Meier method. The Cox proportional hazard model was used for multivariate analysis. ResultsThere were no cases of adenocarcinoma in situ, and three cases of minimally invasive adenocarcinoma. There were 107 cases of invasive adenocarcinoma: 12 lepidic, 32 acinar, 30 papillary, 18 micropapillary, and 15 solid predominant subtypes. Patients with micropapillary and solid predominant tumors had significantly poorer disease-free survival compared to those with other subtypes of predominant tumors (P=0.021). Multivariate analysis revealed that the new classification (P=0.003) and T stage (P=0.034) were independent predictors of disease-free and overall survival, respectively. ConclusionThe predominant subtype in the primary tumor was associated with prognosis in resected stage I lung adenocarcinoma.