Choroidal melanoma is a cancer that grows in the choroid, a thin layer of blood vessels lining the back of your eye between the retina and the outer white wall (the sclera). It is the most common primary cancer that originates inside the eye in adults, with an annual incidence of 6 to 7.5 cases per million people of European descent. While it can appear at any age, the median age at diagnosis is around 63, and it occurs most frequently in people with lighter skin and blue eyes.
Where the Choroid Is and Why It Matters
The choroid is one of the most blood-rich tissues in the entire body. Its primary job is delivering oxygen and nutrients to the outer retina, the layer of light-sensing cells responsible for your vision. It also absorbs stray light inside the eye, helps regulate eye temperature, and plays a role in draining fluid from the front of the eye. Because the choroid is packed with blood vessels, a tumor growing here has relatively easy access to the bloodstream, which is what makes choroidal melanoma a concern beyond just the eye.
Symptoms You Might Notice
Choroidal melanoma is often asymptomatic, especially when tumors are small. Many cases are discovered during routine dilated eye exams when the doctor spots an abnormal pigmented mass. When symptoms do occur, they typically include blurred or decreased vision, flashing lights, or floaters. A tumor pressing on or distorting the retina can cause subtle visual field changes that you might not recognize until they progress. Because a benign choroidal freckle (called a nevus) can look similar, distinguishing between the two is one of the key challenges in diagnosis.
How It Is Diagnosed
The most important diagnostic tool is ultrasound of the eye. On imaging, choroidal melanomas have a characteristic set of features: low internal reflectivity (meaning the sound waves pass through the tumor without bouncing back much), internal blood flow, and a thickness greater than 2 millimeters. When a tumor breaks through a thin membrane called Bruch’s membrane, it takes on a distinctive mushroom or “collar button” shape that is highly suggestive of melanoma. Your doctor will also look for hollowness within the mass and whether it has begun to extend beyond the wall of the eye.
Additional imaging, including optical coherence tomography and sometimes fluorescein angiography, helps characterize the tumor further. A biopsy may be performed in certain cases, particularly when genetic testing of the tumor cells is needed to assess risk.
Tumor Size Classification
Choroidal melanomas are grouped into three size categories based on criteria from the Collaborative Ocular Melanoma Study (COMS), which remains the standard framework for treatment decisions:
- Small: 1.0 to 2.5 mm tall, up to 16 mm across
- Medium: 2.5 to 10 mm tall, under 16 mm across
- Large: over 10 mm tall or more than 16 mm across
Small tumors are sometimes monitored closely rather than treated immediately, because a small percentage turn out to be benign nevi that were initially difficult to classify. Medium and large tumors require active treatment.
Treatment Options
For most medium-sized choroidal melanomas, the standard treatment is plaque brachytherapy, a form of localized radiation. During a short surgical procedure, doctors map the tumor’s location on the outer surface of the eye and suture a small gold disc containing radioactive seeds directly over the tumor site. The plaque stays in place for a calculated period, typically around 4 to 10 days (averaging roughly 6.5 days), delivering a targeted dose of radiation to the tumor while limiting exposure to surrounding tissue. Once the dose is complete, the plaque is removed in a second brief procedure.
For large tumors, or when the tumor has spread through the wall of the eye, or when the eye has lost vision and become painful from tumor complications, surgical removal of the eye (enucleation) is the recommended approach. While this is understandably difficult for patients to consider, it remains the most reliable option for controlling advanced local disease. After enucleation, a prosthetic eye is fitted that closely matches the appearance of the other eye.
Other treatment options for select cases include proton beam radiation and, less commonly, surgical removal of the tumor alone (local resection).
Genetics and Prognosis
What makes choroidal melanoma particularly challenging is that the risk of the cancer spreading depends heavily on the genetic makeup of the tumor itself. About 85 to 90% of these tumors carry a mutation in one of two genes that drive abnormal cell growth. Tumors with a mutation in one of these genes (GNA11) tend to behave more aggressively than those with the other (GNAQ), showing a higher rate of chromosome abnormalities and loss of a key tumor-suppressing protein called BAP1.
Loss of BAP1 and the presence of certain chromosomal changes, particularly losing one copy of chromosome 3 and gaining extra copies of part of chromosome 8, are the strongest predictors of metastasis. This is why many treatment centers now perform genetic testing on tumor biopsies: the results directly inform how intensively you’ll be monitored afterward.
Five-year survival depends on the stage at diagnosis. For early-stage tumors (T1 and T2), five-year survival exceeds 90%. At stage T3, it drops to about 80%, and at stage T4, it falls to roughly 65%.
The Risk of Liver Metastasis
Unlike skin melanoma, which tends to spread to the lungs, brain, or lymph nodes, choroidal melanoma has a strong tendency to spread to the liver. Around 45% of patients eventually develop liver metastases, on average about three years after the initial diagnosis. Only about 2% of patients have detectable metastatic disease at the time the eye tumor is first found, meaning the spread typically happens later, sometimes many years later.
Because of this pattern, long-term liver surveillance is a critical part of follow-up care. There is no universal consensus on exactly how often or with what imaging, but the general approach involves regular liver scans. In Europe, the standard is liver ultrasound every six months for at least 10 years. In the United States, the frequency is tailored to risk: annual imaging for low-risk patients, every 6 to 12 months for medium-risk patients over 10 years, and every 3 to 6 months for the first five years in high-risk patients. MRI is used when ultrasound findings are uncertain.
Treatment for Metastatic Disease
Historically, choroidal melanoma that spread to the liver responded poorly to the immunotherapy and chemotherapy drugs that work against skin melanoma. That changed with the approval of tebentafusp, the first systemic therapy specifically approved for metastatic uveal melanoma. This drug works by connecting two targets: it recognizes a protein found on melanoma cells and simultaneously grabs onto immune T cells, effectively redirecting the immune system to attack the cancer.
Tebentafusp is available to patients who carry a specific immune marker (HLA-A*02:01), which is present in roughly half of people of European descent. In a clinical trial published in the New England Journal of Medicine, patients treated with tebentafusp had a median overall survival of 21.6 months compared to 16.9 months with standard treatment. At three years, 27% of tebentafusp patients were still alive compared to 18% in the control group. Side effects are generally related to immune activation and skin reactions, consistent with how the drug works. While these results represent meaningful progress, the overall survival numbers underscore how serious metastatic choroidal melanoma remains.