Figure 8b. Microscopic features of PVOD. (a) Medium-power photomicrograph (original magnification, x10; H-E stain) demonstrates an edematous interlobular septum (*) that contains a dilated lymphatic, the latter of which is identified by the presence of valves (arrowhead). (b) Medium-power photomicrograph (original magnification, x10; H-E stain) shows loop-like alveolar capillary dilatation (arrow) upstream from a narrowed vein (arrowhead). (c) High-power photomicrograph (original magnification, x40; H-E stain) demonstrates a muscularized arteriole composed of concentric layers of spindle-shaped smooth muscle cells that give the vessel a distinctly rounded configuration; typically, arterioles lack smooth muscle. (d) Medium-power photomicrograph (original magnification, x20; H-E stain) of a muscular pulmonary artery reveals medial hypertrophy (arrowhead) and, in this case, also intimal thickening (arrow).