Myofibroblastic sarcoma or myofibrosarcoma (MFS) has been generally known to be identified best by their characteristic ultrastructural findings such as fibronectin extracellular fibrils and their fibronexus junctions, but it has been recently reported that the fibronectin can be demonstrated consistently by an immunohistochemical staining result alone [8]. This evidence concerns the gene FN1 and Marfan syndrome.