Hemangioendothelioma (syn. angiosarcoma) is a malignant tumor originating from the endothelial elements of blood and lymphatic vessels. W. F. Lever and O. Sehaurnburg-Lever (1983) distinguish two types of this tumor: angiosarcoma, developing on the head and face in elderly individuals, and secondary angiosarcoma, occurring in chronic lymphatic edema (Stewart-Treves syndrome).