CEACAM5 and cancer: This multimarker assay is based on the expression of three genetic markers: carcinoembryonic antigen (CEA), cytokeratin 20 (CK20), and/or cancer stem cells marker CD133 (CEA/CK/CD133) and was shown to be a useful tool for evaluation of CTC as a prognostic factor in PB of colorectal cancer patients [11].