In 2011, a new histologic classification of lung adenocarcinomas was proposed from a joint working group of the International Association for the Study of Lung Cancer (IASLC), American Thoracic Society (ATS), and European Respiratory Society (ERS), based on the recommendation of an international and multidisciplinary panel. This classification proposed a method of comprehensive histologic subtyping (lepidic, acinar, papillary, micropapillary, and solid pattern) based on semi-quantitative assessment of histologic patterns (in 5% increments) with the ultimate goal of choosing a single, predominant pattern. Prognostic subsets could then be described for the classification. Patients with completely resected adenocarcinomas in situ (AIS) and minimally invasive adenocarcinomas (MIA) experienced low risk of recurrence. Patients with micropapillary or solid predominant tumors have a high risk for recurrence or cancer-related death. Patients with acinar and papillary predominant tumors comprise an intermediate-risk group. Herein, we review the outline of the proposed IASLC/ATS/ERS classification, a summary of published validation studies of this new classification and then discuss surgical key issues; we mainly focused on limited resection as an adequate treatment for early-stage lung adenocarcinomas as well as pre- and intraoperative diagnoses. We also review the published studies that identified the importance of histological subtypes in predicting recurrence, both rates and patterns, in early-stage lung adenocarcinomas. This new classification for the most common type of lung cancer is useful for surgeons, as its implementation would require only hematoxylin and eosin (H&E) histology slides, which is the common type of stain used in hospitals. It can be implemented with routine pathology evaluation and with no additional costs.