Precision medicine has renewed the field of medical oncology, allowing a more personalized treatment.

This field in turn has expanded to obtaining and analyzing a vast and every-increasing amount of genomic information.

The liquid biopsy technique consists of detecting and isolating circulating tumor DNA and exosomes.

Many newly developed techniques and next-generation sequencing analyses allow a broad application of liquid biopsy in a wide range of settings.

Some difficulties have been identified in carrying out this procedure, including lack of standardization, presence of confounder genomic information, and lack of appropriate clinical trial designs.

This review summarizes the main techniques and applications of the liquid biopsy technique in cancer.