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Symptoms
Melanocytoma is usually asymptomatic.
Signs
This is a dark grey or black-coloured benign tumour that usually lies over or adjacent to the optic disc. The appearance on fundoscopy is a densely pigmented, elevated lesion. There are feathery borders related to the infiltration of the nerve fibre layer, in a similar fashion to myelinated nerve fibres. Visual acuity is usually normal. Occasional associated signs include optic disc oedema, sheathing of retinal vessels and blind spot enlargement.
Prevalence
Choroidal melanocytoma is rare.
Significance
Choroidal melanocytoma is one of the differential diagnoses of malignant melanoma, a potentially life-threatening condition.
Differential diagnosis
Melanoma, Choroidal naevus, Choroidal haemangioma, Congenital hypertrophy of the retinal pigment epithelium (CHRPE), Combined hamartoma of the retina and RPE.
Management
Additional investigations
Serial photography will be useful in monitoring for growth or change. Visual field assessment may reveal enlargement of the blind spot or any nerve fibre bundle defect.
If there is doubt about the diagnosis, then ultrasonography may help to confirm the diagnosis and the extent of the tumour. Fluorescein angiography of choroidal melanocytoma will show hypofluorescence due to blockage of the choroidal fluorescence by the pigment cells, whereas a melanoma will typically hyperfluoresce due to the vascularity of the lesion.
Prognosis
Lesions infrequently increase in size, and malignant transformation is considered rare. There are reports of spontaneous necrosis of the lesion, or an association with venous occlusion, with the associated risk of neovascular glaucoma.
Review
In general, treatment is not required. Initial review at three-month intervals is recommended to detect growth. Yearly review thereafter is sufficient.