Recent evidence has shown that this metastasis is mediated through specific cell migration stimulated by the interactions of CXCL12, presented by heparan sulphate on the vascular endothelium of organs commonly associated with breast cancer metastasis, with CXCR4, expressed at high levels on metastatic breast cancer cells (Muller et al, 2001). This evidence concerns the gene CXCR4 and breast cancer.