The MIB-1 proliferation index was markedly higher in ESCC with a positive expression of CXCR4 or CXCL12, especially with positive CXCR4 expression (CXCR4 21.8 vs 7.6 %, p = 0.03; CXCL12 17.9 vs 7.6 %, p = 0.20; all percentage values are median). The gene discussed is CXCL12; the disease is esophageal squamous cell carcinoma.