ROS1 and non-small cell lung carcinoma: While for early and locally advanced NSCLC, only EGFR mutational status is mandatory and ALK fusion analysis is optional, in metastatic NSCLC, ALK, ROS1, RET and NTRK rearrangements must be investigated together with EGFR, KRAS, BRAF, HER2 and MET mutations in order to identify those oncogene-addicted tumors that can benefit from targeted therapies.