Melanocytoma of the optic disk: A review

Abstract

Melanocytoma is a deeply pigmented variant of melanocytic nevus that classically occurs in the optic disk, sometimes with contiguous involvement of the adjacent retina or choroid. Historically, this tumor was often confused with malignant melanoma both clinically and histopathologically. Today, however, it is generally recognized by its typical clinical features that differ from most melanomas and erroneous enucleation is rarely done. Histopathologically, melanocytoma is composed of intensely pigmented round to oval nevus cells with benign features. Although traditionally believed to be a relatively stationary lesion, it is now known to exhibit minor enlargement in 10--15% of cases and can cause minor visual loss by a variety of mechanisms. In rare instance, it can induce severe visual loss due to spontaneous necrosis of the lesion or compressive optic neuropathy. More importantly, it can exhibit malignant transformation into melanoma in 1--2% of cases. Ophthalmologists should be familiar with melanocytoma of the optic disk and affected patients should be followed periodically.

Keywords: Choroid; eye; magnocellular nevus; melanocytoma; melanoma; optic disk; optic nerve; pseudomelanoma; retina; tumor; uvea; uveal tract.

Figure 1

Optic disk melanocytoma confined to the optic disk

Figure 2

Optic disk melanocytoma with choroidal component

Figure 3

Optic disk melanocytoma with prominent retinal component

Figure 4

Optic disk melanocytoma with secondary disk edema

Figure 5

Central retinal vein obstruction secondary to melanocytoma of optic disk

Figure 6

Low magnification photomicrograph of optic disk melanocytoma (hematoxylin-eosin 3 10). (Courtesy of Armed Forces Institute of Pathology)

Figure 7

Cytologic features of optic disk melanocytoma. Left: Unbleached section (hematoxylin-eosin 3 100). Right: Bleached section (bleached; hematoxylin-eosin 3 100)

Figure 8

Fluorescein angiography optic disk melanocytoma. Left: Clinical appearance of lesion. Right: Angiogram in mid venous phase showing hypofluorescence of lesion

Figure 9

Optical coherence tomography (OCT) of optic disk melanocytoma. Left: Panoret image shows the darkly pigmented optic disk mass with adjacent retinal infiltration. Right: OCTshows a thin, delicate, echogenic line delineating the anterior aspect of the melanocytoma with abrupt and complete shadowing behind, obscuring all details of the optic disk and adjacent retina