45-year-old male presented with decreased peripheral vision of two-year duration
Denied flashing lights, floaters or curtains
Exam Findings
VAcc: 20/20; 20/20
Pupils: RR OU, no RAPD
IOP: 14; 15
EOM: Full OU
Figure 1: Fundus photograph of the right eye (left panel) showing pigmented dark brown/black lesion covering the disc and appears to be extending to the peripapillary retina with fibrillating margins. Fundus photography of the left eye (right panel) is normal except for mild peripapillary atrophy temporal to the optic disc.
Figure 2:(A) B-scan showing an elevated hyperechoic lesion overlying the optic nerve measuring 1.57mm (height) by 3.76mm (width). (B) A-scan demonstrates that the lesion is of high internal reflectivity.
Differential Diagnosis
Melanocytoma
Juxtapapillary choroidal melanoma
Choroidal nevus
Hyperplasia of the RPE
Combined hamartoma of the retina and RPE
Adenoma of RPE
Metastatic melanoma
Additional Investigations
Fluorescein angiogram was performed to further characterize the lesion (Figure 3)
Humphrey visual field (HVF 30-2) was also obtained (Figure 4) as the patient reported decreasing peripheral vision. In addition, visual field changes have been reported with the most common visual field defect being an enlarged blind spot in approximately 75 to 90 percent of patients with melanocytoma.
Figure 3: Fluorescein angiography of the right eye, early phase (left panel) demonstrates hypofluorescence in the location of the hyperpigmented lesion that persisted on the late phase (right panel).
Figure 4: HVF 30-2 of the right eye (left panel) demonstrates diffusely diminished peripheral visual field with only a small central field maintained. In contrast, the left eye (right panel) represents a normal visual field.
Diagnosis
Melanocytoma
Pathophysiology
Melanocytoma (magnocellular nevus) is a benign tumor considered to be a variant of a melanocytic nevus
The pathogenesis is unknown but it is thought to be either an acquired lesion or a congenital lesion that may start off amelanotic and acquire dense pigmentation with age
Treatment
The patient was followed up with yearly dilated fundus examination with ancillary fundus photography and B-scan ultrasonography to document the dimensions of the lesion.
There are no treatments available to prevent growth of a melanocytoma. Patients are examined at least yearly to ensure there is no growth. More frequent examinations are warranted if there is documented growth with suspicion for possible transformation into a malignant melanoma.
Figure 5: Fundus photography of the melanocytoma in 2014 (left panel) and 2016 (right panel) showing a similar appearance in the size, borders and pigmentation of the lesion.
Prognosis and Future Directions
Majority of melanocytomas do not grow or cause visual symptoms. However, a mild decrease in visual acuity can occur in around 26 percent of patients secondary to retinal exudation, subretinal fluid or optic disc edema.
Severe vision loss is extremely rare, but may occur secondary to a central retinal vein occlusion, tumor necrosis or malignant transformation.
10 to 15 percent of melanocytomas grow over years. An initial thickness ≥ 1.5mm predicts future growth.
Malignant transformation can occur in 1 to 2 percent of cases. Patients typically present with a progressively growing lesion that is associated with decreasing visual acuity.
Other etiologies for a growing melanocytoma include a complication of tumor necrosis that occurs when the melanocytoma outgrows its vascular supply. In addition, a juxtapapillary melanoma needs to be considered in a growing lesion.
MRI can be helpful in determining extent of retrolaminar extension of the lesion especially when suspecting transformation to choroidal melanoma and also aid in the diagnosis of complications of melanocytoma such as tumor necrosis.
References
Shields JA, Demirci H, Mashayekhi A, Eagle RC, Shields CL. Melanocytoma of the optic disk: A review. Surv Ophthalmol. 2006 Mar-Apr;51(2):93-104.
Osher RH, Shields JA, Layman PR. Pupillary and visual field evaluation in patients with melanocytoma of the optic disc. Arch Ophthalmol. 1979;97:1096-1099.
Singh AD, Platt SM, Lystad L, et al. Optic Nerve Assessment Using 7-Tesla Magnetic Resonance Imaging. Ocul Oncol Pathol. 2016 Apr;2(3):178-180.
Meyer D, Ge J, Blinder KJ, Sinard J, Xu S. Malignant transformation of an optic disk melanocytoma. Am J Ophthalmol. 1999;127(6):710-714.
Baartman BJ, Ahmad B, Srivastava S, Jones S, Singh AD. MELANOCYTOMA OR JUXTAPAPILLARY MELANOMA? Retin Cases Brief Rep. 2017 Jan 2.
Filloy A, Arias L, Ascaso FJ, Caminal JM. Swept source optical coherence tomography imaging of optic disc melanocytoma. Clin Exp Ophthalmol. 2016 Oct 11.
Contact
Jesse L. Berry, MD, Assistant Professor of Clinical Ophthalmology and Assistant Director of Ocular Oncology, jesse.berry@med.usc.edu
