It recognizes a protein of 75kDa, identified as Thrombomodulin. Thrombomodulin is a transmembrane glycoprotein with natural anticoagulant properties. It is normally expressed by a restricted number of cells, such as endothelial and mesothelial cells. In addition, synovial lining and syncytio-trophoblasts of placenta also express thrombomodulin. This protein is present in almost all of benign vascular tumors and majority of malignant vascular tumors(Kaposi’s sarcoma,angiosarcoma, and epithelioid hemangioendothelioma).