The neoplastic cells of leiomyomas and leiomyosarcomas are strongly and diffusely positive for smooth muscle actin and desmin but negative for CD34 and CD117 while GISTs are strongly and diffusely positive for CD117, with a cytoplasmic, membranous, or paranuclear “dot-like” pattern [19]. The gene discussed is KIT; the disease is leiomyosarcoma.