CXCR4 and breast cancer: Recently, the “cross-talk” between EGFR and CXCR4 signaling pathways has been observed in many solid malignancies, including non-small cell lung, breast, gastric and ovarian cancers [11–15], and the coexpression of EGFR and CXCR4 might define a new molecular subtype displaying a worse prognosis in non-small cell lung cancer and breast cancer [15], [16].