The melanocytoma is a darkly pigmented benign tumour that usually lies over or adjacent to the optic disc, affecting the choroid and superficial nerve fibre layer. Histologically, it is a variant of a choroidal naevus, composed of polyhedral naevus cells filled with large amounts of densely pigmented cytoplasm. Melanocytoma can also arise in other parts of the uvea, namely the iris or ciliary body. Lesions infrequently increase in size, and malignant transformation is rare.
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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.
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