Choroidal melanoma is a form of eye cancer in which a tumor grows in the choroid layer of the eye. The choroid is a vascular layer of tissue sandwiched between the retina (inside layer of the eye) and the sclera (white outer layer of the eye). The tumor starts as a small nevus, similar to a small freckle or mole. This nevus slowly grows into a melanoma, which can spread to other parts of the body, sometimes leading to death.
According to the Eye Cancer Network website, approximately six out of every million people in North America will develop a choroidal melanoma each year.
How is it detected?
Usually, choroidal melanoma has no symptoms. It is most often detected during a routine eye exam. Occasionally, however, the tumor will seep fluid that forms a pool large enough to separate the retina from the choroid at that position. The patient may then see flashes of light, floating specks, or have blurry vision. These symptoms often lead the patient to get an eye exam.
When a nevus or tumor is discovered during an eye exam, the eye doctor will usually refer the patient to an eye cancer specialist for further examination and proper care. If the nevus is small, the eye cancer specialist may recommend that it be observed for a time to evaluate whether it is growing. If it is not, the nevus may simply be a harmless area of pigmentation, which doesn’t require treatment.
If, after some time, the nevus has gotten larger, the doctor may use a number of diagnostic technologies such as angiography and ultrasound to make a more confidant diagnosis of choroidal melanoma.
How is it treated?
In the past, the usual treatment has been removal of the eye, and that is still a method of treatment for large choroidal tumors. Since about the 1940s, however, radiation treatment has been used to treat choroidal melanomas of small to medium size.
In recent years, this method has been refined to be effective at eradicating tumor cells in small and medium sized tumors without destroying all of the vision of the eye. The main drawback to this method is that the radiation damages much of the vision in the affected eye.
Photocoagulation and transpupillary thermotreatment are also used at times to burn small choroidal tumors, and cryotherapy is used occasionally to freeze them. Regardless of the treatment method, the patient usually loses some vision in the treated eye.
What is the long-term prognosis for someone who is treated for choroidal melanoma?
According to a report from the U.S. National Instututes of Health's National Eye Institute, only about 5% of patients treated for small choroidal tumors will develop a secondary form of cancer in another part of the body within 5 years. For larger choroidal tumors, the odds are about 12% that they will acquire a secondary cancer from their eye tumor.
Because of the potential for this type of cancer to spread, patients who have been treated for a choroidal melanoma should have regular screenings for liver, bone, lung, and skin cancers.
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