title: A low-grade extraskeletal osteosarcoma.
abstract: The case of a 35-year-old woman with low-grade extraskeletal osteosarcoma of the left leg is presented. Radiographs showed peripheral ossification of the lesion, suggesting myositis ossificans. Most of the tumor was composed of cartilage, and the cellularity and cell atypia of the proliferating chondrocytes were mild to moderate. In the periphery, bone formation with a relatively clear margin and proliferation of spindle cells with minimal nuclear atypia were observed. The average percentage of cells positive for MIB-1 was 9.0%. A diagnosis of low-grade extraskeletal osteosarcoma was made on the basis of these histologic findings. The clinical course 47 months after a wide excision was uneventful.
authors.affiliation: Department of Orthopedic Surgery, Akita University School of Medicine, 1-1-1 Hondo, Akita 010-8543, Japan. cshokada@med.akita-u.ac.jp
authors.forename: Kyoji
authors.initials: K
authors.lastname: Okada
authors.forename: Hiroki
authors.initials: H
authors.lastname: Ito
authors.forename: Naohisa
authors.initials: N
authors.lastname: Miyakoshi
authors.forename: Masato
authors.initials: M
authors.lastname: Sageshima
authors.forename: Jun
authors.initials: J
authors.lastname: Nishida
authors.forename: Eiji
authors.initials: E
authors.lastname: Itoi
mesh_terms: D000328:Adult; D002356:Cartilage / Q000473:pathology; D005260:Female; D006801:Humans; D018482:Muscle, Skeletal / Q000473:pathology; D012516:Osteosarcoma / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D011859:Radiography; D012983:Soft Tissue Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery