Lung Adenocarcinoma: Current Classifications and Uncommon Mutations

Due to advances in lung cancer genetics and molecular assessment, the 2015 World Health Organization Classification of Lung Tumors was published with significant changes. Notably, the term bronchioalveolar carcinoma (BAC) was retired and lung cancers previously called BAC were reclassified under various subsets of lung adenocarcinoma. Lung adenocarcinomas can be best diagnosed by larger tissue biopsies and resected specimens. Main histological types include preinvasive lesions, minimally invasive adenocarcinoma, and invasive adenocarcinoma. Invasive adenocarcinomas make up 70–90% of resected lung tumors. Within this histological subtype, molecular abnormalities can further classify lung adenocarcinomas. EGFR, ALK, ROS1, MET, BRAF, RET, and HER2 gene abnormalities are the most common of the uncommon lung adenocarcinomas. Several FDA-approved targeted therapies are available for the treatment of lung adenocarcinoma subtypes and many novel therapies are being tested in ongoing clinical trials.