Purpose: 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.
Patient and 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.
Conclusion: 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.