Ocular melanoma arises from cells called melanocytes, which are the cells of the body that produce pigment. Ocular melanoma is a cancerous (malignant) tumor that can potentially spread (metastasize) to other parts of the body, most often to the liver. The exact cause of this disorder is unknown, but several risk factors have been identified.
Although these choroidal melanocytes are similar to those cells found in the skin that produce skin pigment, when choroidal melanocytes transform into cancerous cells it is called choroidal (or uveal) melanoma. However, cutaneous (skin) melanoma and uveal (ocular) melanoma are distinct conditions which share the same name but are biologically and genetically very different diseases. It is extremely rare for skin melanoma to spread into the eye and nearly unheard of for ocular melanoma to spread to the skin.Signs & Symptoms
Ocular melanoma may or may not cause symptoms. This generally depends on the exact location, size of the tumor within the eye, and if the tumor is causing secondary effects to the retina. An ocular melanoma may not cause any symptoms (clinically silent) for many years before symptoms begin. When symptoms develop they can include:
- blurred vision,
- double vision (diplopia),
- a perception of flashes of light in the eye (photopsia),
- a reduction in the total field of vision, and loss of vision.
Additional symptoms that have been reported include
- a sensation of a foreign body like a speck of dust in the field of vision (floaters),
- bulging or displacement of the eye (proptosis),
- a change in the shape of the pupil,
- pressure within the eye.
Some individuals may develop metamorphopsia, a distortion of vision where, when a person looks at a grid of straight lines, the lines appear wavy and parts of the grid appears blank.
When an ocular melanoma occurs in the choroid, this can lead to detachment of the retina, the nerve-rich membrane lining the back of the eyes. When an ocular melanoma occurs in the ciliary body, it can displace the lens of the eye causing blurry vision from cataract or a rapid change in eyeglass prescription (astigmatism).
An ocular melanoma has the potential to spread (metastasize) to other areas of the body. The liver is the most common organ in the body affected by metastasis of an ocular melanoma (80% of cases) but less often may involve the lungs, skin or soft tissue, and bone. Some estimates suggest that in 40-50% of individuals, an ocular melanoma will metastasize. Based on the aggressiveness of the particular tumor, as defined by clinical and genetic features, metastasis may be detected as early as 2-3 years after diagnosis and rarely as late as decades after treatment. Symptoms will depend upon what part of the body is affected and how long the metastasis has been present. Metastasis is a severe complication of the disease that has a high mortality rare due to lack of definitive treatments to eradicate all metastasis, though recent advances have shown success in certain instances.
There are some differences in metastatic risk based on where in the uveal tract the ocular melanoma develops. For example, iris melanomas have a very low rate of metastasis compared to ciliary body and choroidal melanomas. Advances in genetic testing of individual ocular melanoma tumors has helped to better customize a patient’s risk of developing metastasis independent of the tumor location or tumor size.