Since we found both PDGFR and CXCR4 overexpression in association with SHH MB, and it has been shown that PDGF-D overexpression induces CXCR4 and promotes metastasis in breast cancer cells [14], we postulated that there may be a functional relationship between PDGFR and CXCR4. Here, CXCR4 is linked to breast cancer.