ALK and non-small cell lung carcinoma: An in-depth investigation of copy number alteration (CNA) heterogeneity in phenotypically characterized CTCs at resistance to ALK-TKIs in ALK-positive NSCLC at the single cell level, revealed that, in FACS-isolated CTCs, 37% were ALK+/cytokeratins-, 56% were ALK-/cytokeratins+, and only 5% were ALK+/cytokeratins+.