Liquid biopsy: a right tool in a right context?

Liquid biopsy is a minimally or noninvasive technique for finding that circulates tumor components in biofluids. Generally, blood is used but any biological fluid can be used such as urine, pleural effusion, and saliva. Cells, including cancer cells, release DNA fragments called circulating tumor DNA, which represents a fraction of the circulating free DNA (cell-free DNA) and which represents the main biomarker user, through necrosis and apoptosis mechanisms; it is also possible to use exosomes, that is, subcellular structures encapsulated in the membrane containing proteins and nucleic acids released by tumor cells, microRNA, platelets. In this chapter, we aimed to summarize liquid biopsy applications in a real-world setting.