Vein graft with atherosclerotic plaque containing a lipid-rich necrotic core. A, Picrosirius red stain viewed under polarized light (collagen lights up), the necrotic core is defined by lack of collagen (black area marked with asterisk). B, immunohistochemical stain for smooth muscle cells demonstrates lack of smooth muscle cells in the necrotic core (asterisk) and plenty of smooth muscle cells in the fibrous cap separating the necrotic core from the lumen. C, lectin stain demonstrates neovascularization of the vein graft but also stains macrophages and erythrocyte membranes including the debris from these cell types that can be found in the necrotic core (asterisk). D, immunohistochemical stain for macrophages demonstrates numerous macrophages in the border of the necrotic core (asterisk).