Specificity: This antibody helps to establish the endothelial nature of some lesions of disputed histogenesis, e.g. Kaposi's sarcoma and cardiac myxoma. It is widely used for differentiating vascular lesions from those of other tissue differentiation within a panel of other vascular markers, although not all tumors of endothelial differentiation contain this antigen. Immunogen: Recombinant human vWF fragment spanning aa 845-949.