To examine the diversity of somatic alterations and clonal evolution according to aggressiveness of disease, nineteen tumor-blood pairs of 'formerly bronchiolo-alveolar carcinoma (BAC)' which had been reclassified into preinvasive lesion (adenocarcinoma in situ; AIS), focal invasive lesion (minimally invasive adenocarcinoma; MIA), and invasive lesion (lepidic predominant adenocarcinoma; LPA and non-lepidic predominant adenocarcinoma; non-LPA) according to IASLC/ATS/ERS 2011 classification were explored by whole exome sequencing.