Choroidal melanoma is a rare but serious form of eye cancer that develops in the choroid, a thin layer of blood vessels located between the retina and the outer wall of the eye. Though uncommon, affecting only about 5 to 7 people per million each year, it stands as the most common primary cancer that forms inside the adult eye. Early detection through regular eye examinations can make a significant difference in treatment outcomes and vision preservation.

Who Should Undergo Diagnostic Testing

Most people with choroidal melanoma do not experience symptoms in the early stages, which makes routine eye examinations particularly important. The tumor can remain completely silent for prolonged periods, growing slowly without causing any noticeable changes in vision or comfort. This is why eye care professionals emphasize the value of regular dilated eye exams, especially for people who fall into higher risk groups.^[1]

Certain individuals should be especially vigilant about seeking comprehensive eye evaluations. People with fair skin, light-colored eyes such as blue or green, and those who burn easily in the sun face an increased risk of developing this type of cancer. The incidence is notably higher among Caucasians, with the disease being more common in males than females. Age also plays a significant role, as most cases occur in people around 55 years old, with the peak diagnosis range falling between 70 and 79 years of age.^[1][8]

It is advisable to seek diagnostic testing if you notice any changes in your vision or eye appearance. Symptoms that warrant immediate attention include blurred vision, seeing flashes of light known as photopsias, perceiving floating spots or specks in your vision called floaters, progressive loss of peripheral vision, or distorted vision where straight lines appear wavy. Some people may observe a dark spot growing on the colored part of the eye or notice changes in the shape of the pupil. While eye pain is uncommon in early stages, it can occur if the tumor causes pressure or inflammation within the eye.^[3][4]

Many choroidal melanomas are actually discovered during routine eye examinations before any symptoms appear. This incidental finding during a standard checkup underscores the importance of maintaining regular eye care appointments, even when everything seems normal. The more anterior, or forward, the tumor’s location in the eye, the longer it may take for symptoms to develop, which means some tumors grow considerably before being noticed by the patient.^[3]

Classic Diagnostic Methods

The diagnosis of choroidal melanoma typically begins with a comprehensive eye examination performed by an eye care specialist. This examination involves looking into the eye through a dilated pupil, which allows the doctor to see the back portion of the eye where the choroid is located. During this examination, the specialist uses special equipment such as binocular indirect ophthalmoscopy, which involves lenses and a bright light mounted on the doctor’s forehead, or slit-lamp biomicroscopy, which uses a microscope with an intense beam of light to illuminate the inside of the eye.^[3]

Small choroidal melanomas typically appear as nodular, dome-shaped masses that are well-defined and sit under the retinal pigment epithelium, which is a layer of cells at the back of the retina. As these tumors grow larger, they may adopt more irregular shapes, including bilobular, multilobular, or mushroom-like configurations. The coloration of choroidal melanomas varies widely, ranging from completely colorless tumors called amelanotic melanomas to darkly pigmented ones. Some show partial pigmentation. When a tumor is light in color, doctors can often see abnormal blood vessels feeding it during the examination.^[3][14]

Eye care specialists have developed helpful tools to distinguish choroidal melanomas from benign lesions. One such tool is the mnemonic device “MOST,” which helps doctors identify key features of malignant tumors. The “M” stands for melanoma itself, “O” represents orange pigment called lipofuscin, which is a metabolic byproduct of cell death that appears over or within the tumor. The “S” indicates subretinal fluid, which accumulates when poorly formed blood vessels within the tumor leak. Finally, “T” refers to tumor thickness, with tumors greater than 2.0 millimeters being more likely to be cancerous.^[2]

Ultrasonography stands as the most valued diagnostic test for choroidal melanoma. This technique uses high-frequency sound waves to create images of the eye’s internal structures. There are two types commonly used: A-scan and B-scan ultrasound. A-scan ultrasonography is particularly useful for tumors thicker than 2 to 3 millimeters. Choroidal melanomas show a characteristic pattern on A-scan, beginning with a prominent spike followed by low-to-medium internal reflectivity with decreasing amplitude. Vascular pulsations within the tumor can be seen as fine oscillations in the internal spiking pattern. B-scan ultrasonography provides a two-dimensional view and is routinely used to evaluate any mass at the back of the eye.^[1][3]

Specialized photography plays an important role in diagnosis and monitoring. Fundus photography creates color pictures of the inside surface of the eye, which can show the tumor and any changes over time. Fundus autofluorescence imaging is particularly useful for detecting lipofuscin, the orange pigment that indicates tumor activity. Fluorescein angiography involves injecting a colored dye into a vein in the arm, which then travels to the blood vessels in the eye. A camera with special filters captures images every few seconds, revealing the circulation pattern within the tumor and helping to distinguish melanomas from other conditions.^[2][13]

Optical coherence tomography, or OCT, is a three-dimensional imaging technique that can detect small amounts of subretinal fluid that may not be visible during a standard eye examination or on ultrasound. This high-resolution imaging provides detailed cross-sectional views of the retina and underlying structures, helping doctors assess how the tumor affects surrounding tissues.^[2]

In the landmark Collaborative Ocular Melanoma Study, eye cancer specialists correctly diagnosed choroidal melanoma in over 99.6% of cases without performing a biopsy. This high accuracy rate means that most patients do not need to undergo an invasive tissue sampling procedure to confirm the diagnosis. However, biopsies may be performed in certain situations, such as when the tumor has an atypical appearance, when there is a possibility of metastatic cancer from another part of the body, or when the patient specifically requests pathological confirmation. More recently, biopsies are increasingly performed for genetic testing of the tumor, which can provide information about prognosis and guide treatment decisions.^[2]

Once choroidal melanoma is suspected or confirmed, additional tests are performed to check whether the cancer has spread beyond the eye. The liver is the most common site for choroidal melanoma metastasis, so liver function tests are routinely ordered. These blood tests measure levels of specific enzymes including alkaline phosphatase, glutamic-oxaloacetic transaminase, lactate dehydrogenase, and gamma-glutamyl transpeptidase. Elevated levels of these enzymes may indicate liver involvement.^[3][14]

Imaging studies of the liver and other organs may also be performed. These can include abdominal ultrasound, computed tomography scans, or magnetic resonance imaging to look for any signs that the cancer has spread. A complete general medical checkup is typically recommended as part of the comprehensive evaluation following a choroidal melanoma diagnosis.^[2]

Diagnostics for Clinical Trial Qualification

When patients with choroidal melanoma consider participating in clinical trials, they must undergo specific diagnostic evaluations to determine their eligibility. Clinical trials have strict criteria regarding tumor characteristics, overall health status, and previous treatment history to ensure the study results are valid and that participants are suitable for the experimental intervention being tested.

Accurate measurement of tumor dimensions is essential for clinical trial enrollment. Researchers need precise information about tumor thickness and basal diameter, which is the width of the tumor base. These measurements are typically obtained through ultrasound examination and help classify the tumor as small, medium, or large. Different clinical trials may focus on specific tumor size categories, making these measurements critical for determining eligibility.^[1]

Visual acuity testing is another standard requirement for clinical trial qualification. This involves measuring how well the patient can see using standardized eye charts. The level of vision in both the affected eye and the fellow eye often influences trial eligibility, particularly for studies evaluating vision-preserving treatments. Researchers need baseline visual function data to later assess whether the treatment being studied maintains or improves vision.^[3]

Documentation of the tumor’s location within the eye is necessary for many clinical trials. Whether the tumor arises from the iris, ciliary body, or choroid affects treatment options and prognosis. Detailed fundus photography and ultrasound imaging provide this anatomical information. Some trials specifically target tumors in particular locations or exclude certain sites based on the intervention being tested.

Evidence regarding whether the tumor has spread beyond the eye is critically important for trial eligibility. Most clinical trials for primary choroidal melanoma exclude patients who already have distant metastases, particularly liver involvement. Therefore, comprehensive imaging of the liver and other organs, along with liver function blood tests, must be performed and documented before trial enrollment. Some trials specifically focus on metastatic disease and require proof of spread for participation.^[1]

Genetic testing of the tumor tissue has become increasingly relevant for clinical trial qualification. Researchers have discovered that certain genetic mutations within choroidal melanomas affect how the disease behaves and how likely it is to spread. Trials testing targeted therapies often require specific genetic profiles for enrollment. A biopsy of the tumor may be performed to obtain tissue for genetic analysis, which can identify mutations in genes associated with disease progression.^[2]

General health status assessment is standard for clinical trial screening. This includes a complete medical history, physical examination, and laboratory tests to evaluate kidney function, liver function, blood cell counts, and other vital parameters. These tests ensure that participants are healthy enough to receive the treatment being studied and can safely tolerate potential side effects. Documentation of any other medical conditions or medications is also required, as certain comorbidities may exclude patients from participation or require special monitoring during the trial.

Previous treatment history must be thoroughly documented for clinical trial qualification. Many trials require that patients have not received any prior treatment for their choroidal melanoma, while others specifically enroll patients whose tumors have recurred or progressed after initial therapy. Detailed records of any previous surgeries, radiation therapy, or other interventions must be provided during the screening process.

Confirmation of diagnosis through standardized criteria is essential for clinical trial participation. While biopsies are not always required for routine clinical care, some research studies mandate histological confirmation of the tumor type. This ensures that all participants truly have the disease being studied and reduces variability in trial outcomes. The specific diagnostic criteria used must align with the trial protocol requirements.