We quantified the percentage area of a microscopic field occupied by IBA1+ cells and found that they occupied a considerably higher area in the tumour (9.8 ± 0.3%, mean ± S.E.M., N = 6) than ramified microglia in naive cerebellum (1.2 ± 0.04%, N = 6, Mann–Whitney U test, P < 0.01) (Fig. 1f). This evidence concerns the gene AIF1 and neoplasm.