Antigen-dependent (immunoaffinity-based) methods of isolation utilise antigen recognition to select for or against cells based on markers present on the cell membrane, achieved by immobilising a complimentary antibody or aptamer on a supporting structure.80,81 Positive enrichment selects for CTCs; conversely, negative enrichment excludes non-CTCs.12 These strategies often target epithelial cell adhesion molecule (EpCAM/CD326), as a high proportion (up to 90%) of cancers are of epithelial origin and thus express this marker.12,82–84. Here, EPCAM is linked to cancer.