Extraocular extension of unrecognized choroidal melanoma simulating a primary optic nerve tumor: report of two cases

Orbital extraocular extension of choroidal melanoma is well known and is usually detected in eyes with medium and large tumors, but it is very rare with small melanomas. It is particularly unusual for choroidal melanomas of any size to invade the optic nerve or its meninges.

Two case reports.

Two patients with small, relatively inconspicuous juxtapapillary pigmented choroidal lesions were referred with the diagnosis of primary optic nerve tumor. Both demonstrated a large nodular tumor in the meninges of the optic nerve, immediately posterior to the globe.

Retrospective review of clinical records and histopathology.

In both cases, orbital magnetic resonance imaging confirmed the presence of a hyperintense enhancing nodular mass near the anterior portion of the optic nerve, prompting optic nerve biopsy in one case. Subsequent fundus examination disclosed a small juxtapapillary pigmented choroidal lesion measuring 1.0 mm or less in thickness. These observations suggested that the optic nerve tumor might be nodular extraocular extension of a small choroidal melanoma. Modified enucleation was performed in both cases, and histopathologic examination revealed a nodule of malignant melanoma within the meninges that compressed the optic nerve and extended extraocularly from a small, relatively inapparent juxtapapillary choroidal melanoma. In both cases, the extraocular component was large and symptomatic, whereas the intraocular component was inconspicuous.

Small juxtapapillary choroidal melanomas can exhibit prominent extension into the orbit. All patients with orbital tumors should have careful ophthalmoscopy.