Detection of a population of cancer cells within the circulatory system of cancer patients was first reported in the 1990s by Racila et al., [10] using an immunomagnetic separation and flow cytometry protocol relying on epithelial cell adhesion molecule (EpCAM)-positive expression and anti-CD45 and nucleic dye exclusion of contaminant leukocytes and red blood cells (RBCs), respectively. Here, EPCAM is linked to cancer.