Figure 7

Hemangiomas and hemangiosarcomas induced by intravenous injection of the AAV6 vector expressing JSRV Env. Left panels show tumors stained with a mixture of the B3 and C9 Mab (light methyl green counterstain) and right panels show hematoxylin and eosin staining of the same areas shown in the left panels. Top panels show a large cavernous hemangiosarcoma arising in subcutaneous fat. Boxes indicate the areas shown in the middle panels (black boxes) and lower panels (white boxes). Middle panels show an area typical of hemangioma composed of cavernous blood vessels containing residual red blood cells (RBC) that are lined with a single layer of well differentiated, flattened endothelial cells. Note the intense Env Mab staining of endothelial cells but that the collagen and other cells between the vascular spaces do not stain with the Env Mab. Bottom panels show a high-magnification view of an area of hemangiosarcoma comprised of Env⁺ pleomorphic endothelial cells forming a solid cellular mass. Note examples of pleomorphic nuclei with prominent nucleoli (yellow arrows, lower right panel).