ROS1 and non-small cell lung carcinoma: Moreover, concerning the spreading to the central nervous system (CNS), RET disease shows an intermediate behavior between ALK (anaplastic lymphoma kinase) + and ROS1(ROS proto-oncogene 1) + NSCLC patients; the incidence of brain metastases at the diagnosis was 25% in a retrospective analysis of 185 patients with RET fusion + NSCLC, and around 46% of them developed CNS metastases during their lifespan [30].