title: Malignant transformation of a medulloepithelioma of the optic nerve.
abstract: OBJECTIVE
  To describe a case of malignant transformation of a medulloepithelioma of the optic nerve.
  
  
  METHODS
  A 3-year-old boy presented with right-sided proptosis, swollen eyelids, restricted ocular movements, pain and nausea. Visual acuity was hand motions. A benign non-teratoid medulloepithelioma of the optic nerve was surgically removed. Due to relapse in the orbit 10 months postoperatively enucleation and partial orbital exenteration were performed. Light microscopy and immunohistochemistry now revealed a malignant medulloepithelioma. The boy was further treated with chemotherapy and radiotherapy and is still alive 36 months after primary surgery.
  
  
  RESULTS
  Medulloepithelioma of the optic nerve is extremely rare. Only eight cases have been described in the literature. Unlike intraocular medulloepithelioma, all have been malignant tumours. This is the first case described of a benign medulloepithelioma of the optic nerve, later transforming into a malignant tumour. One third of patients with medulloepithelioma of the optic nerve have died from direct intracranial spread or metastasis to the central nervous system (CNS).
  
  
  CONCLUSIONS
  Medulloepithelioma of the optic nerve should be considered malignant despite morphology with tendency to spread to the CNS. Furthermore; it should be considered as a differential diagnosis when observing a tumour of the optic nerve in a child.
authors.affiliation: Eye Pathology Section, Department of Neuroscience and Pharmacology, University of Copenhagen, and Department of Ophthalmology, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark. JensLindegaard@gmail.com
authors.forename: Jens
authors.initials: J
authors.lastname: Lindegaard
authors.forename: Steffen
authors.initials: S
authors.lastname: Heegaard
authors.forename: Peter Bjerre
authors.initials: PB
authors.lastname: Toft
authors.forename: Karsten
authors.initials: K
authors.lastname: Nysom
authors.forename: Jan Ulrik
authors.initials: JU
authors.lastname: Prause
mesh_terms: D001707:Biopsy, Needle; D002471:Cell Transformation, Neoplastic / Q000473:pathology*; D017024:Chemotherapy, Adjuvant; D002675:Child, Preschool; D005094:Exophthalmos / Q000175:diagnosis / Q000209:etiology; D015353:Eye Enucleation / Q000379:methods; D005500:Follow-Up Studies; D006801:Humans; D007150:Immunohistochemistry; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D009364:Neoplasm Recurrence, Local / Q000473:pathology* / Q000628:therapy; D018242:Neuroectodermal Tumors, Primitive / Q000175:diagnosis / Q000473:pathology* / Q000601:surgery; D019574:Optic Nerve Neoplasms / Q000175:diagnosis / Q000473:pathology* / Q000601:surgery; D017233:Orbit Evisceration / Q000379:methods; D018714:Radiotherapy, Adjuvant; D018570:Risk Assessment; D033581:Stem Cell Transplantation; D016896:Treatment Outcome