When heterologous sarcoma elements such as cartilage or skeletal muscle are present, it is easier to confirm the biphasic nature of the tumor, although immunostains can be of further help such as Myogenin and Myo D1 (rhabdomyosarcoma); smooth muscle actin and desmin (leiomyosarcoma); and S100 (chondrosarcoma). The gene discussed is DES; the disease is rhabdomyosarcoma.