In non-small cell lung cancer (NSCLC), there is a consensus regarding the use of 
liquid biopsy, generally, to detect "druggable" mutations and, in particular, to 
monitor tyrosine kinase inhibitor (TKI) treatments. However, whether circulating 
tumor cells (CTCs) are better tools than cell-free DNA (cfDNA), is still a 
matter of debate, mainly concerning which antigen(s) we should use to 
investigating simultaneously both epithelial and epithelial-to-mesenchymal 
transient (EMT) phenotype in the same sample of CTCs. To address this item, we 
exploited here a single-tube liquid biopsy, to detect both epithelial cell 
adhesion molecule (EpCAM)-positive CTCs and EpCAM-low/negative CTCs, because 
down-modulation of EpCAM is considered the first step in EMT. Furthermore, we 
analyzed the DNA from CTCs of four different phenotypes (ctcDNA), according to 
their EpCAM expression and cytokeratin pattern, and circulating tumor DNA 
(ctDNA) by droplet digital PCR (ddPCR), in order to disclose activating and 
resistance-driving mutations. Liquid biopsy reflected spatial and temporal 
heterogeneity of the tumor under treatment pressure. We provide the 
proof-of-concept that the complementary use of ctDNA and ctcDNA represents a 
reliable, minimally invasive and dynamic tool for a more comprehensive view of 
tumor evolution.