Figure 2. . Main aspects of conventional tissue biopsy and liquid biopsy.

Tumor tissue represents the gold standard for molecular investigations but some problems exist regarding its obtainment and utility. In fact, apart from the invasiveness of the practice, tissue biopsy can give molecular information just at the diagnosis time and does not permit the detection of cancer heterogeneity and molecular cancer evolution. A valid non-invasive approach to assess the molecular profile of patients is through a liquid biopsy, where cancer biomarkers can be analyzed through a biofluid sample. CTCs, ctDNA and exosomes can offer a fast and non-invasive method to elucidate the genetic heterogeneity of patients and patients can give a dynamic surveillance for tumor progression and monitor treatments response.

cfDNA: Circulating-free DNA; CTC: Circulating tumor cell; ctDNA: Circulating tumor DNA; ncRNA: Non-coding RNA.