Choroidal Melanoma : Causes, Risk Factors, Symptoms, Staging and Treatment

Choroidal melanoma is a cancer of the eye affecting the choroid, the part of the Uvea which is the middle layer of the eye. Melanomas are the cancer of pigment-producing cells known as melanocytes. Cancer occurring in the melanocytes of the eye is known as ocular melanoma.

The eye consists of three layers:⁽¹⁾

• The outer layer includes the white of the eye, the sclera, and the cornea.
• Middle layer or the uvea which contains the iris, ciliary body, and choroid.
• Inner layer or the retina

Choroidal melanoma affects the choroid in a person. It is observed that choroidal melanoma is larger than the melanoma of the iris and spreads more.⁽¹⁾

Despite being the most common uveal melanoma, choroidal melanoma is very rare. Research shows that 5-6 in 1 million people develop uveal melanoma every year.⁽²⁾

According to the American Cancer Society, 90% of uveal melanoma are choroidal or ciliary body melanoma.⁽³⁾

The exact cause of choroidal melanoma is unknown. Genetic and environmental factors are believed to be the cause of choroidal melanoma.

There are certain risk factors that may increase the chance of a person developing ocular cancer, including:

• Having light skin tone
• Having light-colored eyes
• Having freckles
• Being an older adult
• Being unable to get tan
• Having atypical moles

Initially, a person with choroidal melanoma may not show any symptoms. In an article, it was stated that 30% of people with choroidal melanoma do not have any symptoms.⁽⁴⁾

If the people with choroidal melanoma show symptoms, they may include:

• Visible tumors
• Blurry vision
• Flashes of light in the vision
• Pain
• Retinal detachment
• Loss of vision in a particular area in the visual field

Metamorphopsia, a condition in which straight lines appear to be curved.

Spread and metastasis of any type of cancer are determined by TNM classification, which is based on:

• T: Size and extent of tumor
• N: Spread to nearby lymph nodes
• M: Spread to distant areas

After the TNM classification is done, staging and grouping for specific cancer are done. Stage groupings for choroidal melanoma include:⁽¹⁾

• Small: A tumor with 1-3 mm in height and 5-16 mm across
• Medium: Tumor with 3-18 mm height and not larger than 16 mm across
• Large: Tumor with 8 mm height and larger than 16 mm across

Ocular melanomas are detected during a routine dilated eye examination. Further testing may be needed to diagnose choroidal melanoma.

A biopsy involves taking a sample or fluid from the potential cancer site. During the procedure, a thin needle is inserted into the eye. A person may be given local or general anesthesia during the procedure.

Mostly biopsy is not recommended to test choroidal melanoma as it can cause cancer to spread.

The imaging tests done to detect choroidal melanomas include:

• Ultrasound: In it, sound waves are used to build images of the inside of the body.
• Optical coherence tomography: It is a scan in which light waves produce a cross-section of a person’s eye. It can be helpful in detecting the location and features of choroidal melanoma.
• MTI scan: It uses strong magnetic and radio waves to produce an image of the inside of a person’s body.

In fluorescein angiography, a dye is injected into a person’s arm, which travels to the blood vessels of the eye. A special camera is used to take images of the eyes. This can help in revealing any damage or tumor.

The treatment of choroidal melanoma depends on its size.

In the case of small and medium-sized choroidal melanoma, the treatment options may include:

• Radiation Therapy: In this, radiation is used to destroy or shrink the tumors. There is a type of radiation therapy known as brachytherapy, in which radioactive material is inserted into the eye and is removed after a few days. Proton therapy is another option in which proton beams are directed into the eyes to destroy tumors.
• Laser Therapy: It involves delivering focused light to the eyes to destroy tumors.
• Surgery: In this, an area affected with choroidal tumor is removed.  If a lot of eye damage has occurred, the surgeon might need to remove the eye completely.

For large choroidal tumors, the treatment options include radiation therapy or surgery.

People with choroidal melanoma do not have a positive outlook.⁽²⁾ According to research, the disease-free survival time for a person with choroidal melanoma is 26 months.⁽⁵⁾

The outlook also depends on the person’s age, the spread of cancer, and the size of the tumor.

Early detection is important for choroidal melanoma. A person experiencing symptoms should see the doctor immediately. It is also important for people to go for a regular eye health check as choroidal melanoma does not always produce symptoms.