CXCR4 and metastatic malignant neoplasm in the lymph nodes: Moreover, as staining for CXCL12 and CCL21 (or CXCR4 and CCR7) was tightly linked in the group of primary tumors and lymph node metastasis tumors in this study, it is likely that a shared mechanism may account for variations in expression levels of both molecules in breast cancer.