Tumor-infiltrating macrophages and angiogenesis in AR-DLBCL. (A) The proportion of CD68⁺ macrophages does not differ significantly between HIV-infected and uninfected patients, and between pre-HAART and post-HAART era patients (top). We noted comparable expression of CD68 and CD163 antigens by tumor-infiltrating macrophages in AR-DLBCL, as shown in this example (bottom). CD163 is a classic marker of anti-inflammatory or alternatively activated (M2) macrophages corresponding to the hemoglobin-haptoglobin scavenger receptor. (B) Microvessel and sprout densities for AR-DLBCL compared with sporadic DLBCL. AR-DLBCL is characterized by a substantially higher amount of neovascularization: the mean (±SD) microvessel and sprout count were 32.2 ± 13.2 per hpf and 10.2 ± 6.3 per hpf, respectively, whereas in sporadic DLBCL the corresponding values were significantly lower, 20.6 ± 8.3 and 5.5 ± 3.7 (P < .001 and P < .001, respectively). (C) Immunohistochemical analysis of CD34⁺ endothelial cells in 3 representative cases: (i) EBV-positive immunoblastic AR-DLBCL, (ii) EBV-negative centroblastic AR-DLBCL, and (iii) EBV-negative sporadic DLBCL centroblastic type, with respective microvessel counts of 52.22, 29.91, and 16.61 per hpf. All specimens represent lymph node biopsies of hyperproliferative lymphomas without c-Myc translocation. Images were taken with a Leica DM2500 microscope (original magnification, ×200), Leica DFC320 camera.