Expression of CD13 by endothelial cells and pericytes in primary CNS lymphoma vasculature. High-resolution wide-field co-immunofluorescence analysis of PCNSL tissue sections from 2 enrolled patients. The sections were stained with a polyclonal anti-CD13 antibody (green) and polyclonal anti-CD31, a marker of endothelial cells (red). Nuclear staining with 4′,6-diamidino-2-phenylindole (DAPI; blue). (A-C) Examples of vessels with CD13⁺ endothelial cells (arrows, yellow in the merged figure) and CD13⁺ mural cells (arrowheads, green, likely pericytes). See also supplemental Movie 1 for z-stack images of the vessel reported in panel A. (C) Central panel: electronic enlargement of the highlighted area (dashed rectangle) of the vessel shown in the left panel. Right panel (control): a consecutive tissue section with secondary antibodies alone, showing lack of staining. (D) Examples of vessels with CD13⁺ mural cells (arrows, green) and CD13^– endothelial cells (arrowheads, red) in the merged figure. Scale bar, 5 µm; magnification is shown in each panel.