Orbital neurofibrosarcoma in a dog.

A young dog was presented with rapidly progressive, unilateral, exophthalmos. Ultrasound-guided fine-needle aspiration of the retrobulbar mass resulted in a diagnosis of fibrosarcoma. Magnetic resonance imagery revealed tumor invasion into the brain, and palliative therapy was elected. The dog was euthanized 4 weeks following diagnosis due to progressive neurological signs. The final diagnosis was neurofibrosarcoma involving the pons, brainstem, left orbit and left trigeminal nerve.