A new classification of adenocarcinoma: what the radiologists need to know

The International Association for the Study of Lung Cancer, American Thoracic Society, and European Respiratory Society recently introduced a new classification of lung adenocarcinoma addressing the latest advances in oncology, molecular biology, pathology, radiology, and surgery of lung adenocarcinoma. In this classification, new uniform terminology and diagnostic criteria are described, including the introduction of adenocarcinoma in situ as a second preinvasive lesion, as well as the concept of minimally-invasive adenocarcinoma and new subtyping of invasive adenocarcinomas stratified according to predominant patterns. In addition, the previously widely-used term bronchioloalveolar carcinoma is no longer considered valid and has been recategorized. This classification also provides, for the first time, guidance for small biopsies and cytology specimens. This new classification has profound implications for radiology, as much investigation will be needed to correlate these newly introduced concepts (such as histologic subtypes) with radiologic features. Understanding the newly described concept of minimally-invasive adenocarcinoma will be essential in determining sublobar resection for adenocarcinomas. In this manuscript, we briefly review the new classification of lung adenocarcinoma and discuss its radiologic relevance to the reporting, biopsy, and future studies of adenocarcinoma.