Zhao J, et al. - Given that ROS1 immunohistochemistry (IHC) using D4D6 antibody is useful for screening patients with non-small-cell lung cancer (NSCLC) who may be suitable for targeted therapy, authors attempted to study the driver mutation and clinicopathological characteristics of 26 discordant cases (ROS1 IHC-positive but FISH-negative) to find new ways for distinguishing real ROS1-rearranged cases. In younger patients and at an advanced stage, ROS1-rearranged NSCLCs were significantly more likely to be found. ROS1-discordant patients exhibited distinct clinical and morphological features and often harbored another oncogenic driver alteration vs ROS1-rearranged cases. It was noted that the use of optimized screening criteria will increase the specificity of a ROS1 antibody.