Indeed, FISH of CTCs identified on the surface of filters after blood filtration led to the detection of different gene mutations but also gene amplifications and rearrangements, notably in ALK, ROS1, MET and RET [35] Conversely, the evaluation of genomic alterations with cf-DNA extracted form blood of late stage lung cancer patients has been routinely performed for many years [33]. The gene discussed is RET; the disease is lung carcinoma.