Extraskeletal osteosarcoma has a favourable prognosis when treated like conventional osteosarcoma. - Goldstein-Jackson,S.Y.; Gosheger,G.; Delling,G.; Berdel,W.E.; Exner,G.U.; Jundt,G.; Machatschek,J.N.; Zoubek,A.; Jurgens,H.; Bielack,S.S. (J Cancer Res Clin Oncol, 2005)