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). Hence, anti-thrombomodulin serves as a sensitive marker for lymphatic endothelial cells and their tumors. Recently, thrombomodulin antibody has been used for mesothelial cells and malignant mesotheliomas.