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Uveal Melanoma: What is it?

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By Sapna Patel, M.D., assistant professor, Department of Melanoma Medical Oncology

Eye cancerUveal melanoma is a term with which many people may be unfamiliar. In part, that's because it's a relatively rare type of cancer, but also because it's been called different names by different sources.

Essentially, uveal melanoma is a cancer, or melanoma, of the eye. While it's not seen as often as cutaneous (skin) melanoma, which accounts for the vast majority of melanoma cases, it's the second most common type of primary malignant melanoma in the body. It represents an estimated 5% to 6% of all melanoma diagnoses.

Uveal melanoma involves one of the three parts of the eye that comprise the uvea: the iris, the ciliary body and the choroid. The National Cancer Institute (NCI) provides useful information on uveal melanoma under the heading of intraocular melanoma, defined as a disease in which malignant cells form in the tissues of the eye.

Intraocular disease starts in the middle layer -- the uvea -- of the wall of the eye. The uvea is located behind the sclera (the white of the eye) and the cornea, the window at the front of the eye. Of the three main components of the uvea, the iris is the colored area of the eye.

Behind the iris is the ciliary body, a ring of tissue with muscle fibers that alter the size of the pupil and the shape of the lens. The choroid (also known as the posterior uvea) is a layer of blood vessels that bring oxygen and nutrients to the eye; this is where most intraocular (hence, uveal) melanomas develop.

Risks and symptoms

According to the NCI, risk factors for intraocular melanoma are: 

  • being exposed to natural or artificial sunlight over long periods of time (although this remains controversial); 
  • being fair-skinned, with light-colored eyes; 
  • older age; 
  • and being white.
Blurred vision, a change in vision, a dark spot on the iris or a change in the shape of the pupil may be symptoms of this disease, or could be traced to other conditions. So, a doctor's visit is in order if any of these occur, the NCI advises.

However, intraocular melanoma may not cause early symptoms of any kind. Sometimes, it's found when the ophthalmologist dilates the patient's pupils and can see into the eyes.

Intraocular melanoma can be treated and controlled for long periods of time, and vision can usually be saved in patients with small tumors that haven't spread.

This underscores the importance of regular eye examinations by an ophthalmologist, early diagnosis, and early evaluation and treatment by experienced melanoma professionals such as those at MD Anderson.

About nine of 10 intraocular melanomas develop in the choroid, according to the American Cancer Society (ACS). 

Nearly all the remaining intraocular melanomas start in the iris. An iris melanoma is the easiest type of melanoma to see, as it often starts in a pigmented spot that has been present for years but then begins to grow, the ACS notes.

There's no known inherited genetic mutation that's causative for uveal melanoma, but new insights are revealing clusters of families in whom uveal melanoma exists. In these patients, there may indeed be a germline, or inherited, mutation in a gene known as BAP1.

This gene may predispose patients to other types of cancer, including mesothelioma, breast cancer and colon cancer. Research is actively being pursued regarding this finding and its epidemiological and genetic implications. 

A review of uveal melanoma trends from 1973 to 2008, published in September 2011 in Ophthalmology 1, showed the age-adjusted incidence in the United States -- 5.1 per million -- remained unchanged. Despite a shift from surgery alone toward more conservative treatments, survival didn't improve during that time.

However, research has produced recent treatment breakthroughs, which I'll discuss in future posts. Information on melanoma treatments and clinical trials at MD Anderson is available by calling (locally) 713-792-3245 or (long distance, toll free) 1-877-632-6789.

Resources
1.Singh AD et al. Uveal melanoma: trends in incidence, treatment and survival. Ophthalmology 118 (9):1881-1885, 2011.

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