Strategies for enrichment of circulating tumor cells

Circulating tumor cells (CTCs) are cells derived from the primary sites of tumor patients into peripheral blood and serve as seeds that initiate tumor metastasis to distant sites. As a primary form of "liquid biopsy", CTC enumeration has exhibited great potential as a mean to obtain diagnostic and prognostic biomarker information in various cancers. The comprehensive clinical utility of CTC tests, however, is still restricted due to the scarcity and heterogeneity of CTCs, which necessitates reliable techniques for their efficient enrichment and characterization. Numerous methods have been developed to improve yield and purity of CTC enrichment as well as detection sensitivity. In this review, we comprehensively summarize techniques for CTC enrichment and detection.