The New 2011 International Association for the Study of Lung Cancer/American Thoracic Society/European Respiratory Society Classification of Lung Adenocarcinoma in Resected Specimens: Clinicopathologic Relevance and Emerging Issues

Pathologists play an increasingly important role in personalized medicine for patients with lung cancer as a result of the newly recognized relationship between histologic classification and molecular change. In 2011, the International Association for the Study of Lung Cancer/American Thoracic Society/European Respiratory Society (IASLC/ATS/ERS) proposed a new architectural classification for invasive lung adenocarcinomas to provide uniform terminology and diagnostic criteria. This review highlighted the evolution of the classification of lung adenocarcinomas in resected specimens with special respect to both histologic subtyping and invasion. Histologic subtyping of lung adenocarcinoma has been updated based on five major predominant patterns. New concepts of adenocarcinoma in situ and minimally invasive adenocarcinomas have been introduced to define the condition of patients who are expected to have excellent survival. Although the new IASLC/ATS/ERS classification has promising clinical relevance, significant clarification remains necessary for the definitions of subtyping and invasion. More precise definitions and subsequent better education on the interpretation of terminology will be helpful for future studies.