ROS1 and mesenchymal cell neoplasm: ROS1 rearrangement has been found not only in the epithelial tumors, such as non-small cell lung cancer (NSCLC), ovarian cancer, gastric adenocarcinoma, and colorectal cancer, but also in some mesenchymal tumors, such as IMT, angiosarcoma, and leiomyosarcoma [14–17].