The majority of tumor-infiltrating mast cells expressed CXCR4 but not CCR2, CCR4, CCR5, CCR7, CXCR1, CXCR2 or CXCR7 (Fig. 2a; Additional file 7: Figure S2c), while, mast cells in peritumoral or non-tumor tissues showed lower CXCR4 expression (Fig. 2a). The gene discussed is ACKR3; the disease is neoplasm.