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Choroidal melanoma

 

 

Uveal melanoma is a malignant tumour arising from melanocytes. Intraocular melanoma develops within the choroid, ciliary body or iris. Extraocular melanoma develops in conjunctiva or skin.

 

Intraocular (or ‘uveal’) melanomas affect about one person in every 2500 whereas conjunctival melanomas affect one person in every 125,000. Both tumours tend to affect adults. The cause is unknown, although as with skin melanomas, ocular melanomas tend to be more common in individuals with fair skin, light-coloured eyes, and a tendency to sunburn.

 

Choroidal melanoma

Choroidal melanoma, arises beneath the retina. If untreated, it can:

  • Cause retinal detachment, with blurred vision, distorted vision, flashes of light and a visual field defect;
  • Perforate the retina, to cause vitreous haemorrhage (i.e., bleeding into the jelly of the eye), with floaters and blurred vision;
  • Grow through the sclera (i.e., wall of the eye) to invade the tissues around the eye.

 

Small choroidal melanomas can be difficult to distinguish from large naevi (which are benign). Features suggestive of malignancy are:

  • clumps of orange pigment on the tumour surface
  • serous retinal detachment
  • thickness exceeding 2 mm
  • involvement of the optic disc.

small-choroidal-melanoma-with-orange-pigment

Small choroidal melanoma with orange pigment

 

 

medium-dome-choroidal-melanoma

 This photograph shows a dome-shaped choroidal melanoma in the left eye with secondary retinal detachment.

 

A small minority of choroidal melanomas are diffuse. These are relatively aggressive and more likely to have extended extra-ocularly by the time of diagnosis and treatment.

 

diffuse-choroidal-melanoma

Diffuse choroidal melanoma obscuring the right optic disc

 

Investigations

These include:

  • Visual assessement by slit-lamp examination, ophthalmoscopy and colour photography
  • Angiography in selected cases
  • Ultrasonography, to measure the tumour dimensions and extent
  • Biopsy in selected cases, to confirm the diagnosis and/or for prognostication

 

Treatments

Treatment depends on the size and location of the tumour and the patient's needs and concerns. Methods include:

Prognosis

The chances of conserving vision and the eye depend on:

  • tumour dimensions
  • proximity of tumour to optic nerve and fovea
  • extent of involvement of iris an ciliary body
  • size of any extraocular spread
  • co-existing ocular disease
  • systemic disease, such as diabetes mellitus

 

The chances of developing metastatic disease correlate with:

  • intraocular tumour dimensions, particularly the largest basal tumour diameter
  • involvement of ciliary body
  • extraocular spread
  • epithelioid melanoma cytomorphology
  • closed laminin loops
  • high mitotic rate
  • partial or complete deletion of chromosome 3
  • gains in chromosome 8