title: Mesenchymal chondrosarcoma of the orbit.
abstract: OBJECTIVE
  To describe a patient with mesenchymal chondrosarcoma of the orbit, review clinical and imaging findings, and refine the differential diagnosis from other tumors of the orbit.
  
  
  METHODS
  Interventional case report and literature review.
  
  
  RESULTS
  A 21-year-old woman with a 6-month history of progressive proptosis presented with left-sided visual loss of recent onset. CT revealed a clearly outlined heterogeneous mass with calcified foci, whereas MRI showed an isointense signal to gray matter on T1- and T2-weighted images. The patient was diagnosed with mesenchymal chondrosarcoma of the orbit only after orbitotomy and subsequent histopathologic study. After surgery, she received adjuvant therapy with irradiation of the orbit.
  
  
  CONCLUSIONS
  Mesenchymal chondrosarcoma is a rare malignant tumor of the orbit capable of mimicking several other lesions. Early diagnosis requires a high level of suspicion, particularly with regard to internally calcified lesions. The treatment of choice is complete surgical resection, or, when the tumor is not resectable or residual mass is present after surgery, chemotherapy and radiotherapy. Prognosis for patients with orbital mesenchymal chondrosarcoma is tentative at best, in part because of the rarity of the lesion.
authors.affiliation: Division of Ophthalmology, Hospital das Clínicas of the University of São Paulo Medical School, São Paulo, Brazil.
authors.forename: Hélio
authors.initials: H
authors.lastname: Angotti-Neto
authors.forename: Leonardo P
authors.initials: LP
authors.lastname: Cunha
authors.forename: Angela V
authors.initials: AV
authors.lastname: Oliveira
authors.forename: Mário L R
authors.initials: ML
authors.lastname: Monteiro
mesh_terms: D000328:Adult; D018211:Chondrosarcoma, Mesenchymal / Q000175:diagnosis* / Q000532:radiotherapy / Q000601:surgery; D003937:Diagnosis, Differential; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008279:Magnetic Resonance Imaging; D013508:Ophthalmologic Surgical Procedures / Q000379:methods; D009918:Orbital Neoplasms / Q000175:diagnosis* / Q000532:radiotherapy / Q000601:surgery; D018714:Radiotherapy, Adjuvant; D014057:Tomography, X-Ray Computed