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Uveal melanoma is a rare cancer, but it’s the most common primary cancer of the eye in adults. Primary means that the cancer begins in the eye. Sometimes, cancer that starts in the eye can spread to other parts of the body. This can happen as early as 2 years after diagnosis to decades after treatment. Cancer cells will spread to other parts of the body in about half of adults who have uveal melanoma. No one knows why this type of cancer spreads, but understanding how it spreads and where it spreads to can help in your efforts to fight the disease.

How Does Cancer Spread?

Some types of cancers spread through the lymphatic system. One of the many functions of the lymphatic system is to transport and remove waste products and abnormal cells from the fluids that are drained from your cells and tissues. Damaged cells, cancer cells, bacteria, and viruses are some of the substances that are removed drained from the fluid. The eye does not have lymphatic vessels. So, the uveal melanoma cells – for the most part – spread through the blood. The cancer cells arrive at other parts of the body by floating in the blood stream, and then growing in the new place.

Uveal melanoma spreads to the liver more than other places. This may be because of the liver’s large supply of blood and other fluids that encourage cell growth. The blood flow to the liver is only second to the blood flow to the lung.

Uveal melanoma also can spread to other places in the body, although less often:

  • Liver -- 90%-95%
  • Lungs -- 24% 
  • Bones -- 16%
  • Skin -- 11%
  • Lymph nodes -- 14.4%
  • Brain -- 10%

What Determines How Uveal Melanoma Spreads?

The risk of the uveal cancer spreading is determined by many factors, such as the size of the tumor, location, and genetic profile.

  • Tumor size: Size is the most important aspect when figuring out how uveal melanoma will progress. Increasing tumor thickness is associated with risks for spread. One study showed that each millimeter increase in tumor thickness was associated with approximately 5% increased risk for spread at 10 years.
  • Tumor location: If the cancer is mainly in the area of the eye called the ciliary body, it can progress more quickly and have a higher risk of spreading. This may be because the spread is affected by the movement of the muscle in the ciliary body that is used when the eye focuses. It may also be affected by how close the tumor is to the ciliary blood vessels. 
  • Genetic profile: Mutations (changes) in five specific genes have been identified that can affect uveal melanoma. Some of those mutations happen as the disease progresses. Some of these mutations can be associated with how much the uveal melanoma may spread. As genetic testing advances, doctors may be able to customize treatments to lower patients’ risk that their cancer will spread. Also, depending upon the type and stage of uveal melanoma, your doctor may recommend that you meet with a genetic counselor to discuss your risks, possible future risks to your family members, and what tests might be helpful. Looking into the genetics that may play a part in uveal melanoma often requires a team effort that includes specialists in cell biology and genetics.

Iris melanoma is the least common site for uveal metastatic melanoma. This type of melanoma is usually smaller and slower growing than other types. It is associated with a melanocyte, which is a cell that contains coloring (melanin). People with light-colored skin and blue eyes are more likely to have this type of the disease.

Ciliary body and choroidal melanomas have a greater rate of spreading than iris melanomas. The ciliary body is a ring of muscle tissue found behind the iris that changes the size of the pupil. The choroid is a layer of blood vessels that bring oxygen and nutrients to the eye. Melanomas located in the ciliary body tend to be larger, and they are more likely to spread than those in the iris.

When you read about survival rates, realize that they are estimates based on information collected about large numbers of people who have had the same cancer over a period of time. Each person’s body reacts a bit differently, so doctors can’t predict what will happen in each person’s case. Survival rates for uveal melanoma depend on many factors, such as age, overall health, where the cancer started, and how well the cancer responds to treatment.

Finding uveal melanoma early is vital to slowing or stopping the spread of this disease. Every day, people whose uveal melanoma has spread benefit from research advances that result in more effective treatment. Uveal melanoma can be treated systematically to extend your life and improve your quality of life.

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