title: Two unusual osteogenic orbital tumors: presumed parosteal osteosarcomas of the orbit.
abstract: OBJECTIVE
  To report two cases of suspected parosteal osteosarcoma of the orbit, with dedifferentiation into a high-grade liposarcoma occurring in one patient.
  
  
  METHODS
  Two retrospective case reports.
  
  
  METHODS
  The clinical, radiologic, and pathologic records of two patients with suspected orbital parosteal osteosarcoma were retrospectively reviewed.
  
  
  METHODS
  Histologic evaluation and clinical follow-up were measured.
  
  
  RESULTS
  The first patient was a 47-year-old male presenting with a 5-month history of painless right lower lid swelling; excision biopsy suggested a well-differentiated parosteal osteosarcoma of the orbital floor, which recurred 3 years later. Six months after excision of the recurrence, the mass demonstrated accelerated growth, and a lid-sparing exenteration was performed; histologic examination showed a high-grade liposarcoma. The patient remains disease-free at 4 years. The second patient, a 40-year-old male, presented with an 8-year history of proptosis and a right superotemporal orbital mass. The mass was excised completely at lateral orbitotomy; histologic examination suggested a well-differentiated parosteal osteosarcoma. The patient remains well 9 months postoperatively.
  
  
  CONCLUSIONS
  Parosteal osteosarcoma is an uncommon tumor, usually affecting long bones, that is extremely rare in the orbit. It is a low-grade sarcoma that tends to recur locally after excision but has a favorable prognosis. Dedifferentiation into a high-grade sarcoma occasionally occurs in parosteal osteosarcoma, but transformation into liposarcoma does not seem to have been previously reported. It is important to recognize dedifferentiated parosteal osteosarcoma, because the prognosis is poor, and radical treatment may be required.
authors.affiliation: Orbital Clinic, Moorfields Eye Hospital, London, England.
authors.forename: D N
authors.initials: DN
authors.lastname: Parmar
authors.forename: P J
authors.initials: PJ
authors.lastname: Luthert
authors.forename: I A
authors.initials: IA
authors.lastname: Cree
authors.forename: R P
authors.initials: RP
authors.lastname: Reid
authors.forename: G E
authors.initials: GE
authors.lastname: Rose
mesh_terms: D000328:Adult; D006801:Humans; D008080:Liposarcoma / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D009918:Orbital Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D018217:Osteosarcoma, Juxtacortical / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed