Ishida H, et al. - Researchers reviewed patients with lung adenocarcinoma who underwent surgery between 2007 and 2014, to determine distinguishing clinicopathological features, in addition to histological invasiveness, in adenocarcinoma in situ (AIS) and minimally invasive adenocarcinoma (MIA) of the lung. Of overall 629 patients, they reviewed 91 (14%) of 103 AIS (n = 34) or MIA (n = 69) tumors were reviewed. A remarkably higher ratio of male to female patients was reported for MIA vs AIS. Non-mucinous tumors were 99 (96%) of 103 tumors. Computed tomography (CT) demonstration of AIS and MIA revealed pure ground-glass nodules appearance in 74% of AIS and part-solid ground-glass nodules appearance in 75% of MIAs. For MIAs vs AIS, significantly greater pathological tumor diameters and Ki-67 labeling index (LI) values were observed. The presence of an MIA was indicated by a Ki-67 LI of ≥2.8%. In MIAs vs AIS, epidermal growth factor receptor (EGFR) mutations were more frequently detected ie, 33/69 vs 9/34, respectively. Findings revealed similar surgical outcomes for AIS and MIAs. These findings demonstrate the validity of classifying the two subtypes.