title: Osteosarcoma arising from  osteochondroma of the tibia: case report and cytogenetic findings.
abstract: Osteochondroma  is a cartilage capped benign tumor developing mainly at the juxta-epiphyseal  region of long bones. The rate of malignant transformation, mainly into  chondrosarcoma, is estimated to be less than 1-3%. Transformation into  osteosarcoma is very rare and has been reported only thirteen times. There is  little information on treatment and outcome. We report the case of a secondary  osteosarcoma arising in the left tibia of a 23-year-old male, 10 years after  the initial diagnosis of osteochondroma and after two partial resections.  Malignant transformation occurred at the stalk and not at the cartilage cap, as  would normally be expected. Chromosome banding analysis revealed the karyotype:  46,XY, t(3;13)(q21;q34) [2]/46,XY [18]. Records from additional cases will help  determine the parameters that define these rare secondary bone lesions.
authors.affiliation: Departamento de Biomecânica, Medicina e Reabilitação do Aparelho Locomotor, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brasil. engel@fmrp.usp.br
authors.forename: E E
authors.initials: EE
authors.lastname: Engel
authors.forename: M H
authors.initials: MH
authors.lastname: Nogueira-Barbosa
authors.forename: M S
authors.initials: MS
authors.lastname: Brassesco
authors.forename: G E B
authors.initials: GE
authors.lastname: Silva
authors.forename: E T
authors.initials: ET
authors.lastname: Valera
authors.forename: F M
authors.initials: FM
authors.lastname: Peria
authors.forename: T C
authors.initials: TC
authors.lastname: Motta
authors.forename: L G
authors.initials: LG
authors.lastname: Tone
mesh_terms: D000328:Adult; D001859:Bone Neoplasms / Q000235:genetics / Q000473:pathology / Q000601:surgery; D002871:Chromosome Banding / Q000379:methods; D006801:Humans; D059785:Karyotype; D008297:Male; D015831:Osteochondroma / Q000235:genetics / Q000473:pathology*; D012516:Osteosarcoma / Q000235:genetics / Q000473:pathology / Q000556:secondary* / Q000601:surgery; D013977:Tibia / Q000473:pathology*; D055815:Young Adult