Here, we identify that CD45+Ly6GmiLy6CloCD11b+ subpopulation are predominately expanded and recruited in systemic and local tumor microenvironment during breast cancer progression and metastasis, which expresses CXCR2 at high proportion, then we named this subset CXCR2+ MDSCs. The gene discussed is CXCR2; the disease is neoplasm.