A 63-year-old Hispanic female was referred for evaluation of a “black spot” located in the fundus of her left eye. Recently, a neurologist examined the patient following a stroke that involved the right side of her brain one month earlier. The neurologist noted a dark lesion in her left eye upon direct ophthalmoscopy.

The patient reported a near full recovery from the stroke, with some residual weakness in her left shoulder. Her only visual complaint was poor near vision, which was corrected with over-the-counter reading glasses. This was her first eye exam.

Her systemic history was significant for hypertension. Current medications included lisinopril and low-dose aspirin.

On examination, her visual acuity was correctable to 20/20 OD and 20/25 OS. Extraocular motility was full, and the adnexal examination was unremarkable OU. Confrontation visual fields were full to careful finger counting OU. Her pupils were equally round and reactive to light, with no evidence of afferent defect. The anterior segment examination showed early nuclear sclerotic cataracts OU. Intraocular pressure measured 14mm Hg OD and 15mm Hg OS.

Dilated fundus examination of the right eye was unremarkable. Examination of the left fundus revealed the presence of a dark lesion; however, the macula and periphery were unremarkable.

Take the Retina Quiz

Fundus photograph of our patient’s left eye shows a peculiar lesion involving the optic nerve. What is the correct diagnosis?

1. Which test is necessary to help establish the diagnosis?

a. Fluorescein angiography.
b. Echography.
c. Excisional biopsy.
d. No tests are necessary.

2. What is the correct diagnosis in this case?

a. Choroidal melanoma with optic nerve involvement.
b. Optic nerve melanoma.
c. Combined hamartoma of the retinal pigment epithelium (RPE) and retina.
d. Melanocytoma.

3. What is the most appropriate treatment?

a. Iodine 125 plaque brachytherapy.
b. Enucleation.
c. External beam radiation, followed by enucleation.
d. Observation.

4. What is the likely five-year mortality rate for this patient?

a. 0%.
b. 15%.
c. 40%.
d. 70%.

For answers, scroll down.

Discussion
Ophthalmoscopic examination of our patient’s left eye revealed the typical clinical picture of an optic nerve melanocytoma, which is nothing more than a benign pigmented tumor involving the optic nerve. Melanocytomas are often dark brown to black in color, and may appear slightly elevated with feathery edges. These lesions typically extend from the optic nerve, over the disc margin, to involve the nearby choroid or sensory retina.¹

Melanocytomas commonly present unilaterally and often are diagnosed near age 50. Researchers have suggested that these lesions are not recognized early because they are not large enough or sufficiently pigmented to be recognized on examination until later in life.²

The primary differential diagnosis for melanocytoma is juxtapapillary choroidal melanoma. Melanomas typically are not as black as melanocytomas. Instead, they exhibit a more mottled gray or yellow-white appearance, and do not insinuate into the nerve fiber layer. Further, choroidal melanomas are more frequently seen in lighter pigmented individuals, and are exceedingly rare in both blacks and Asians. By contrast, melanocytomas are seen with greater frequency in dark-complected individuals. In fact, the presence of a pigmented lesion involving the optic nerve in a black patient is highly suggestive of a melanocytoma.

Melanocytoma is reported to occur more frequently in females; however, there is no known reason for this predilection.¹ Additionally, no strong systemic associations for melanocytoma have been found.¹

Ocular complications from melanocyoma include optic disc edema, subretinal fluid, intraretinal edema, yellow exudates, focal hemorrhage, vitreous seeding and retinal vein obstruction. Complications leading to visual symptoms occur in approximately 26% of patients with melanocytoma.^1,2 Intraretinal tumor extension, as well as the presence of subretinal fluid, have been known to cause vision loss. Afferent pupillary defect occurs in 9% to 30% of cases.²

Traditionally, melanocytoma was considered an indolent lesion that does not grow; however, researchers have noted that 15% of these lesions show some slow enlargement over a number of years.¹ Interestingly, there is a small risk of malignant transformation in an estimated 1% to 2% of cases.¹ Risk factors for malignant transformation include progressive growth and visual field loss, as well as no juxtapapillary choroidal involvement.

Keep in mind that the aforementioned features also can occur in ischemic tumor necrosis, and therefore cannot be used as the only criteria for determining malignant transformation.¹

Diagnosis of melanocytoma often is confirmed by ophthalmoscopic examination. Additional testing may include fundus photography, fluorescein angiography, visual field examination and optical coherence tomography (not to make the diagnosis, but rather to evaluate the impact on the patient’s vision as well as establish a baseline for follow-up testing). OCT imaging isn’t useful in evaluating the specific features of melanocytoma; but, it can help determine the presence and extent of subretinal fluid or intraretinal edema, which may be difficult to see otherwise.¹

Some level of visual field loss occurs in up to 90% of patients with melanocytoma. Enlarged blind spot is the most common visual field defect; however, arcuate and nerve fiber bundle defects may also occur.

The prognosis for patients with melanocytoma typically is excellent. At the time of diagnosis, patients should be photo-documented as well as undergo visual field testing to establish a baseline.¹ Follow-up should be performed yearly, with a dilated examination and fundus photography to monitor for subtle growth.

We discussed the findings with our patient and asked her to return for a visual field examination in four to six months. Future follow-up visits also will provide us with the opportunity to monitor for lesion enlargement.

Thanks to Jacob Woldt, OD, resident at Bascom Palmer Eye Institute in Miami, for contributing this case.

1. Shields JA, Demirci H. Malanocytoma of Optic Disc in 115 Cases: The 2004 Samuel Johnson Memorial Lecture, Part 1. Ophthalmology. 2004 Sep;111(9):1739-46.
2. Shields JA, Demirci H, Mashayekhi A, et al. Malanocytoma of the optic disk: a review. Surv Ophthalmol. 2006 Mar-Apr;51(2):93-104.

Answers
1. d
2. d
3. d
4. a