Disease Overview

Summary

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Ocular melanoma is an extremely rare type of cancer that occurs in about 5 out of every million adults. Despite its rarity, it is the most common primary cancer of the eye in adults. A primary cancer means that the cancer begins in the eye itself and has not spread there from another part of the body. The exact cause of ocular melanoma is unknown, but several risk factors have been identified, including genetic factors and possibly environmental influences. Despite this uncertainty, early detection and treatment are crucial for the best outcomes.

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Introduction

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Eye (ocular) cancer can refer to any cancer that starts in the eye.

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The eye is a complex organ with three main parts:

1. Eyeball (globe): The main part of the eye, filled with a jelly-like substance called vitreous humor. It has three layers:

   • Sclera: The tough, white outer layer

   • Uvea: The middle layer, responsible for nourishment and containing the eye’s pigmented cells

   • Retina: The innermost layer, which senses light and is crucial for vision

2. Orbit: The tissues surrounding the eyeball

3. Adnexal structures: These include accessory parts like the eyelids and tear glands

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Different types of cancer can develop in these areas depending on the type of cells involved. Ocular melanoma typically arises from cells called melanocytes, which produce pigment. When these melanocytes in the choroid become cancerous, the condition is known as choroidal or uveal melanoma. Although these melanocytes are similar to those in the skin, skin melanoma and ocular melanoma are distinct conditions, each with different biological and genetic characteristics. It is rare for skin melanoma to spread to the eye or vice versa.

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Uveal melanomas

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Ocular melanoma can start at the uveal tract, the colored layer of tissue beneath the white of the eye (sclera). The uvea consists of three parts:

1. Iris: The colored part of the eye which surrounds the pupil

2. Ciliary body: A ring of muscle tissue that releases aqueous humor (a clear fluid) and helps control the lens’s shape for focusing

3. Choroid: The largest part of the uveal tract, located at the back of the eye beneath the retina. This area is rich in blood vessels and pigmented cells.

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Most ocular melanomas develop in the choroid or ciliary body. About 9 out of 10 intraocular melanomas occur in these areas. Iris melanomas are less common and usually easier to detect because they often start as a dark spot on the iris that grows over time. Iris melanomas are generally slow-growing and rarely spread, leading to a relatively good prognosis.

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Uveal melanomas can spread through the bloodstream, most often reaching the liver, where the cancer can become life-threatening.

Conjunctival melanomas

The conjunctiva is a thin, clear layer covering the sclera. Conjunctival melanomas are extremely rare but tend to be more aggressive. They can grow into nearby structures and spread through both the blood and lymphatic systems, reaching distant organs like the lungs, liver or brain.

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Full Report Link @ https://rarediseases.org/rare-diseases/ocular-melanoma/

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