Ocular Melanoma (Cancer of the Eye)
Ocular melanoma, a rare cancer, 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. If there is melanoma that starts in the iris, it may look like a dark spot on the iris. 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. Ocular melanoma is usually found during a routine eye examination, when a doctor looks inside the eye with special lights and instruments.
The chance of recovery (prognosis) depends on the size and cell type of the cancer, where the cancer is in the eye, and whether the cancer has spread.
Ocular Melanoma Locations
Ocular melanoma can occur in a variety of ocular tissue.
- Ocular melanomas of the iris occur in the front colored part of the eye. Iris melanomas usually grow slowly and do not usually spread to other parts of the body.
- Ciliary body/choroid (small size)
- Ocular melanomas of the ciliary body and/or choroid occur in the back part of the eye. They are grouped by the size of the tumor. Small size ciliary body or choroidal melanoma is 2 to 3 millimeters or less thick.
- Ciliary body/choroid (medium/large size)
- Ocular melanomas of the ciliary body and/or choroid occur in the back part of the eye. They are grouped by the size of the tumor. Medium/large size ciliary body or choroid melanoma is more than 2 to 3 millimeters thick.
- Extraocular extension
- The melanoma has spread outside the eye by extending through the wall of the eye, the sclera.
- Recurrent disease means that the cancer has come back (recurred) after it has been treated.
- Metastatic melanoma means that the tumor has spread far from the eye, usually to the liver.
Most melanomas of the iris, ciliary or choroid are initially completely asymptomatic. As the tumor enlarges, the tumor may cause distortion of the pupil (iris melanoma), blurred vision (ciliary body melanoma) or markedly decreased visual acuity from a secondary retinal detachment caused by a choroidal melanoma. 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 melanomas. Like most early cancers, an early melanoma is usually a silent cancer.
Determining that the Lesion is a Malignant Melanoma
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.
The symptoms described above may not necessarily mean that you have ocular melanoma. However, if you experience one or more of these symptoms, contact your eye doctor for a complete exam.
Once a definite diagnosis of malignant melanoma is made, possible therapies depend on the location and size of the tumor. Metastatic melanoma can be difficult to treat. In this situation, the ocular melanoma has spread far from the eye and typically has spread to the liver.
Small melanomas of the iris or ciliary body can sometimes be successfully treated with surgery. An iridectomy refers to removal of part of the iris where the tumor is present. An iridocyclectomy refers to removal of part of the iris as well as the adjacent ciliary body where the tumor is present. With very large tumors, the only possible option is removal of the eye, which is called enucleation. Following removal of the eye, an artificial eye is placed in the socket. With today's techniques, it can be extremely difficult to differentiate the artificial eye from the adjacent normal eye.
A special form of radiation therapy has shown to be very effective in treating malignant melanomas of the ciliary body or choroid. This special form of radiation therapy is called plaque therapy which consists of suturing a small metallic object, containing radioisotopes, to the wall of the eye adjacent to the base of the tumor. Once the tumor has received sufficient radiation to destroy the tumor, the plaque is again removed surgically.
The Collaborative Ocular Melanoma Study
The Collaborative Ocular Melanoma Study (COMS) is the largest study of the treatment therapies of ocular melanoma. The COMS initially addressed the question whether additive therapy (radiation therapy) would be of benefit to patients with large choroidal malignant melanoma. In patients with large melanomas, the only reasonable option is removal of the eye, which is called enucleation. Despite removal of the eye, these patients have an increased risk of subsequently developing metastatic disease and dying from their ocular melanoma. In COMS, with full patient agreement, patients were randomized to enucleation of the eye or preoperative radiation followed by enucleation of the eye. Unfortunately, both groups had essentially identical outcomes. The preoperative radiation did not reduce subsequent metastatic disease.
Patients with medium tumors can be treated with either enucleation or a special form of radiation therapy, called plaque therapy. 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.
The COMS evaluated whether enucleation or plaque therapy would be more effective in preventing subsequent metastatic disease. With full patient agreement, patients were randomized to either enucleation or plaque therapy and followed for 10 years to determine which therapy would reduce metastatic disease and death. The study showed that plaque therapy is equally effective as removal of the eye in preventing metastatic disease and death. Thus plaque therapy has become the standard of care for most patients with ocular melanoma.
For more information, see the Ocular Oncology Service at the U-M Kellogg Eye Center.