A malignant neoplasm affecting the skeletal or smooth muscles. malignant neoplasms arising from the skeletal muscles are called rhabdomyosarcomas. malignant neoplasms arising from the smooth muscles are called leiomyosarcomas. check for "https://www.cancer.gov/about-cancer/treatment/clinical-trials/intervention/c4883" active clinical trials using this agent. ("http://ncit.nci.nih.gov/ncitbrowser/conceptreport.jsp?dictionary=nci%20thesaurus&code=c4883" nci thesaurus)