We found a significant reduction in the percentage of mononuclear myeloid cells (monocytes and macrophages) from 63 ± 6 to 25 ± 4% (mean ± S.E.M., N = 9, Fig. 4c), and a corresponding increase in microglial cells from 18 ± 3 to 47 ± 6% (Fig. 4d) in Ccr2-deficient tumour-bearing mice. Here, CCR2 is linked to neoplasm.