Optic nerve glioma a dog

An 11-year-old male Labrador presented with unilateral blindness associated with intraocular haemorrhage and glaucoma. No further diagnostics were performed and enucleation was performed. The clinician noted that the optic nerve appeared grossly thickened.

Fig 1. The globe has been sectioned in half. The optic nerve is thickened (red arrow) and replacing the optic nerve head is a firm white tumour that protrudes into the vitreous (blue arrow). The adjacent choroid is mottled white-brown consistent with tumour invasion. The retina is detached (white arrows) and there is intraocular haemorrhage.
Fig 2. Immunostaining for GFAP (glial fibrillary acidic protein) reveals strong immunopositive brown staining of the tumour cells which supports astrocytic origin (x200).

Final Diagnosis

Optic nerve glioma (astrocytoma)


Gliomas are neoplasms that arise from glial cells (e.g. astrocytes and oligodendrocytes). They most commonly occur in the brain and spinal cord however in rare cases, they may also arise in the optic nerve or retina. Infiltrative behaviour is typical but the risk of metastasis (e.g. to the lungs) is low. The concern in this particular case would be local recurrence at the level of the transected optic nerve and spread along the optic nerve tract. Seeding via the CSF to other areas of the brain is also a possibility. The tumour in this case is associated with choroidal invasion, retinal detachment and intraocular haemorrhage, the last two of which predispose to the formation of pre-iridal fibrovascular membranes (PIFMs). PIFMs form along the anterior face of the iris and extend into the drainage angle resulting in secondary neovascular glaucoma.