Juvenile pilocytic astrocytoma of the optic nerve diagnosed by fine needle aspiration biopsy.

Fine needle aspiration biopsy of an orbital mass was performed under CT guidance in a nine-year-old boy presenting with rapidly increasing proptosis of the right eye with lateral displacement and no light perception. The cytologic findings consisted of bipolar astrocytes with cytoplasmic fibrillated processes intermingled with Rosenthal fibers. A cytologic diagnosis of juvenile pilocytic astrocytoma was advanced; this was confirmed by subsequent histologic study of the surgical specimen. The differential diagnosis among juvenile pilocytic astrocytoma, neurilemmoma and meningioma of the optic nerve are discussed.