title: Fluorescence in situ hybridization (FISH) detects clonal instability in an optic nerve relapse of acute lymphoblastic leukemia.
abstract: OBJECTIVE
  We report a case of an isolated optic nerve relapse 3.5 years after diagnosis of hyperdiploid acute lymphoblastic leukemia (ALL) in a 6-year-old boy who had been off treatment for 3 months. The use of interphase fluorescence in situ hybridization (FISH) for clonal identification of chromosome abnormalities is described.
  
  
  METHODS
  An asymptomatic lesion over the right optic nerve head was identified on routine funduscopic exam. Fine needle aspiration of the optic nerve infiltrate provided tissue for morphologic, immunohistochemical, and FISH analyses.
  
  
  RESULTS
  FISH showed similar but not identical chromosome makeup of the leukemic blasts at the time of relapse as compared to tissue samples obtained at the time of diagnosis.
  
  
  CONCLUSIONS
  Despite antimetabolite therapy, hyperdiploid ALL can rarely recur isolated to an optic nerve. FISH is a useful adjunct for confirming relapse when low numbers of white blood cells are obtained with fine needle aspiration.
authors.affiliation: Department of Pediatrics, University of New Mexico Health Sciences Center, Albuquerque 87131-5311, USA.
authors.forename: B E
authors.initials: BE
authors.lastname: Small
authors.forename: M
authors.initials: M
authors.lastname: Wood
authors.forename: T S
authors.initials: TS
authors.lastname: McConnell
authors.forename: S S
authors.initials: SS
authors.lastname: Winter
mesh_terms: D001707:Biopsy, Needle; D002648:Child; D002869:Chromosome Aberrations; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D019574:Optic Nerve Neoplasms / Q000175:diagnosis* / Q000235:genetics; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000175:diagnosis* / Q000235:genetics; D012008:Recurrence