RAPID GROWTH OF AN OPTIC-NERVE GANGLIOGLIOMA IN A PATIENT WITH NEUROFIBROMATOSIS-1

Background: Optic nerve gangliogliomas are extremely rare tumors of th e central nervous system composed of elements of glial and neuronal or igin. The clinical and biologic behavior of gangliogliomas depends on the glial component. Pilocytic gangliogliomas generally have a low gro wth rate and good ultimate prognosis. No definitive relation has yet b een established between gangliogliomas and neurofibromatosis type 1. M ethods: The authors describe the clinical, histologic, and immunohisto chemical features of an optic nerve ganglioglioma with several atypica l findings. A review of the literature is provided. Results: An optic nerve glioma was diagnosed in a 16-year-old patient who had signs of n eurofibromatosis type 1; the atypical clinical course involved a rapid progression of symptoms with a significant increase in tumor size. Th e tumor was removed surgically and found to be a ganglioglioma compose d of pilocytic glial cells (immunoperoxidase-positive for glial fibril lary acid protein) and neurons (immunoperoxidase-positive for neuron s pecific enolase, synaptophysin, and neurofilament). A focal astrocytic area showed increased cellularity, several mitotic figures, and an el evated labeling index with Ki-67 immunoperoxidase staining. Conclusion : Optic nerve gangliogliomas are rare tumors that cannot be distinguis hed clinically from pilocytic astrocytomas. Although these tumors usua lly grow slowly, careful follow-up is advised. The atypical histologic features are considered to be a manifestation of rapid local growth r ather than a harbinger of malignant behavior. The authors' findings su ggest that gangliogliomas may be included in the diagnostic criteria f or neurofibromatosis type 1.