How does uveal melanoma spread?

Uveal melanoma is a type of cancer that begins in the eyeball. More specifically, it begins in the middle layer of the eyeball called the uvea. While uveal melanoma begins in this part of the eye, it can spread beyond the eye to other parts of the body.

The spread of cancer is called metastasis. Metastasis is common with uveal melanomas, affecting as many as half of all people who have this type of cancer.

Here, we look at how uveal melanomas begin, how they can metastasize, and what this means for treatment.

How does uveal melanoma begin?

To understand how uveal melanomas begin and spread, it helps to have an overview of the anatomy of the eye and the uvea. The uvea includes three parts:

• The iris, the colored section of the eye.
• The ciliary body, which produces the fluid that fills the eye and contains a muscle that enables the eye to focus.
• The choroid, a cluster of blood vessels and connective tissues.

It also helps to have a basic understanding of melanomas. Like other cancers, melanomas are the uncontrolled growth of cells. This uncontrolled growth begins when normal cells undergo mutations that cause them to divide at a faster rate and expire at a slower rate.

Melanomas begin when this type of mutation occurs in cells called melanocytes. These cells produce a substance called melanin. Melanin acts as a pigment that gives eyes their color and helps protect the eye’s light-sensitive cells (called photoreceptor cells) from UV radiation.

Other types of melanocytes are found in the skin and also act as pigments, but skin melanomas and uveal melanomas are very different conditions.

Uveal melanoma is more common in males, more common in people with light-colored skin and eyes, and more likely to occur as a person gets older. It is not understood if things like sun exposure or having skin melanoma are risk factors, and the causes of uveal melanoma are not fully understood.

How does uveal melanoma metastasize?

Uveal melanomas spread much in the same way that other cancers spread. As the primary tumor grows in size, it can extend into surrounding tissues, including blood vessels. From there, cancer cells can break off and travel through the bloodstream to other parts of the body, where new tumors begin to grow. (Keep in mind that this is a simplified explanation of a complex process.

The most common area of the body for uveal melanoma to spread to is the liver. Liver metastasis occurs in roughly 90 percent of cases of metastatic uveal cancer. Metastasis to the lungs, bones, and skin are less common, but also occur in a significant percentage of cases. Metastasis to the lymph nodes and brain are not common, but they do occur.

How is uveal melanoma treated?

Metastasis is an important consideration in treatment for uveal melanoma. In most cases, metastasis occurs after a person has been diagnosed with uveal melanoma.

Assessing the risk of metastasis and preventing metastasis will be an important focus of treatment. In cancers that have already metastasized when a person is diagnosed, treatment will address both the primary tumor in the eye, as well as tumors in other sites in the body, such as the liver.

Treatment is individualized, meaning the treatments used will vary from person to person. Surgery and radiation therapy are the main treatment options. Chemotherapy and other anticancer drugs may be used as an aggressive treatment option, but are only recommended in some cases.

It’s also worth mentioning that research into new treatments is ongoing. In 2022, the first drug specifically indicated for the treatment of metastatic uveal melanoma became available in the United States. This drug can be used in people who are HLA-A*02:01 positive. HLA-A*02:01 is a genetic variation that can be identified using a blood test.