What Is Uveal Melanoma (Ocular Melanoma)?
Ocular melanoma or, more specifically, uveal melanoma is a the most common primary intraocular (within the eye) cancer in adults. It is a disease in which cancer (malignant) cells are found in the part of the eye called the uvea. The uvea contains cells called melanocytes. When these cells become cancerous, the cancer is called a melanoma. The uvea includes the iris (the colored part of the eye), the ciliary body (a muscle in the eye), and the choroid (a layer of tissue in the back of the eye).
The iris opens and closes to change the amount of light entering the eye. The ciliary body changes the shape of the lens inside the eye so it can focus. The choroid layer is next to the retina, the part of the eye that makes a picture. Most uveal melanomas originate in the choroid, followed by the ciliary body, and the iris. Uveal melanoma is grouped as small, medium, and large based on tumor size.
Uveal melanoma involves 5 to 6 cases per million people per year and, for people over 50 years of age, the incidence rate increases to approximately 21 cases per million per year.
People with choroidal or ciliary body melanoma may not have any symptoms and the tumor might be detected during routine examination. Symptoms may include decreased or blurry vision. Patients with iris melanoma may notice a dark spot on the colored part of the eye or a distorted pupil. If melanoma is in the ciliary body or the choroid, a person may have blurry vision or may have no symptoms, and the cancer may grow before it is noticed. Uveal melanoma is usually found during a routine eye examination, when a doctor looks inside the eye with special lights and instruments.
The exact cause of uveal melanoma is unknown, but people with fair skin, blonde or red hair, and blue or green eyes have a higher incidence.
Uveal melanoma is more common in people who have atypical mole syndrome, dysplastic nevus syndrome, and ocular or oculodermal melanocytosis.
Tests and Diagnosis
Most melanomas are detected by routine ophthalmic examination, which should include dilation of the pupil and detailed examination of the posterior aspect of the eye to detect choroidal melanoma. Like most early cancers, an early melanoma is usually a silent cancer.
One of the difficulties in diagnosing small melanomas is that it can be very difficult to differentiate a small malignant melanoma from a benign pigmented tumor, such as an iris or choroidal nevus. At present there is no definitive test that clearly differentiates a nevus from a small malignant melanoma. Even with special biopsy techniques, such as fine needle aspiration of the lesion, it can be very difficult to differentiate a benign nevus from a malignant melanoma. A distinguishing feature of a small malignant melanoma from a nevus is that the malignant melanoma progressively grows and enlarges. Thus, small lesions may initially be observed to determine if the lesion remains static or shows evidence of progressive growth.
Treatment and Drugs
Surgical excision of tumor, also known as iridectomy or iridocyclectomy, can be used for small, circumscribed iris and ciliary body melanomas with removal of part of the iris as well as the adjacent ciliary body. Main treatment options for iris, ciliary body and choroid melanoma include radioactive plaque therapy and enucleation. Plaque therapy consists of a small gold carrier (something like a small bottle cap), which contain radioactive seeds that can destroy or inactivate tumors. The plaque is sutured to the wall of the eye (sclera) in the operating room and is left in place until the tumor is destroyed. Studies in the literature show that the rate of subsequent metastasis is similar for patients who had plaque radiotherapy and those who had enucleation for medium-sized choroidal melanoma.
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Reviewed by Hakan Demirci, M.D.