(A,B) Autoradiography performed on resected tumors and tissue confirm [11C]PBR28 radiotracer uptake in kidney (positive control) and tumors from wild type mice (n = 3 mice, 5 tumors) while little uptake is seen in muscle (negative control) and tumors for CD11b−/− mice (n = 2 mice, 3 tumors). (C,D) When normalized to uptake in muscle, tumors from wild type mice displayed significantly higher radiotracer uptake than those from macrophage-depleted mice.