The neoplasm formerly known as BAC.

As you may know, a new international multidisciplinary classification of lung adenocarcinoma has recently been published and is sponsored jointly by the International Association for the Study of Lung Cancer, American Thoracic Society, and European Respiratory Society. The panel included international experts in oncology, pulmonology, pathology, radiology, molecular biology, and thoracic surgery who worked collaboratively to address recent advances in adenocarcinoma, the most common histology of lung cancer. The ultimate goal of the new classification system is to assist in determining therapy and predicting outcome for patients with lung adenocarcinoma. One of the major recommendations of the panel is to discontinue the use of the terms ‘‘bronchioloalveolar cell carcinoma (BAC)’’ and ‘‘mixed subtype adenocarcinoma’’. In place of these terms, the classification system introduces new terminology, including ‘‘adenocarcinoma in situ (AIS)’’ and ‘‘minimally invasive adenocarcinoma (MIA)’’ to describe small solitary adenocarcinomas with either pure lepidic growth (AIS) or predominant lepidic growth with r 5mm invasion (MIA) to define patients who will have 100% or near 100% disease specific survival, respectively, following surgical resection. Why was it necessary to discontinue the use of ‘‘BAC,’’ a term associated with both widespread name and pattern recognition among radiologists? The problem is that this term was being used to describe a broad spectrum of neoplasms with variable survival rates. The new classification system provides more precise terminology that appropriately distinguishes entities that are now referred to as MIA and AIS from more aggressive invasive adenocarcinomas. A detailed review of the classification system has recently been published in the February 2011 issue of the Journal of Thoracic Oncology. This article provides an informative series of recommendations and ‘‘considerations for good practice’’ for pathologists, clinicians, radiologists, and surgeons. For example, radiology considerations for good practice include using thin-section CT images for measuring part-solid nodules, with separate measurements for recording the size of the solid component and total nodule size (solid and ground glass components). The article also includes a stimulating series of research questions for each specialty. For example, radiology research questions relate to the natural history of ground glass nodules, optimization of nodule measurement techniques, use of CT attenuation to differentiate among adenocarcinoma histological subtypes, and correlation of imaging and molecular features of lung adenocarcinoma, among others. I would like to bring to your attention 2 articles in this current issue of JTI that relate to the new lung adenocarcinoma classification system. First, in our ‘‘Expert Opinion’’ feature, Drs Teri Franks, Jeff Galvin, James Jett, and David Naidich provide their perspectives on the potential role of image-guided, percutaneous lung biopsy in the assessment of part-solid lung nodules within the context of the new classification system. Second, in our web-exclusive feature ‘‘Notes from the 2010 Annual Meeting of the Korean Society of Thoracic Radiology,’’ the new classification system is employed in a series of informative radiologicpathologic correlation cases. I look forward to continued dialogue about this important and timely topic in future issues of JTI. With this new classification system in place, it is my hope that the term ‘‘BAC’’ will ‘‘RIP. ’’