In a murine model of spontaneous lymphatic metastasis of breast cancer, primary breast tumor mediates the accumulation of B cells in the TDLNs, and B cells promote lymphatic metastasis by producing pathogenic IgG that targets glycosylated membrane protein HSPA4 and activates the HSPA4-binding protein ITGB5 in tumor cells and the downstream Src/NF-κB pathway to achieve CXCR4/SDF1α-induced lymphatic metastasis. Here, HSPA4 is linked to breast neoplasm.