It is believed that tumour metastasis and cancer cell arrest in the vasculature is facilitated through the tethering of circulating cancer cells to vascular endothelium through the interaction of molecules such as CD15s, CA 19-9 and CD44 variants on the tumour cell surface and selectins (CD62-P, -L and –E) expressed on endothelial cells, neutrophils, monocytes, NK cells or platelets [152–155]. This evidence concerns the gene CD44 and cancer.