Uveal melanoma is a form of cancer that originates from melanocytes, the pigment-producing cells located in the eye. This cancer develops within the uvea, the middle layer of the eye wall. The uvea itself has three distinct parts: the iris, which is the colored part of the eye; the ciliary body, a structure that produces eye fluid and helps with focus; and the choroid, a layer of blood vessels that nourishes the retina. While it is the most common primary eye cancer in adults, it remains a rare disease overall.
Symptoms and Risk Factors
A significant number of uveal melanomas are discovered during routine eye examinations because they often do not produce any symptoms in their early stages. When symptoms do occur, they can manifest as a sudden increase in “floaters,” which are spots drifting in the field of vision, or flashes of light. Other signs may include blurred vision, a noticeable dark spot on the iris, or a change in the shape of the pupil. These symptoms can also be associated with other, less serious eye conditions.
Individuals with light-colored eyes, such as blue or green, and fair skin have a higher risk. The risk also increases with age. Certain inherited conditions, like having a mutation in the BAP1 gene, can predispose individuals to this cancer at a younger age. The presence of numerous moles on the skin or specific types of freckles within the eye, known as nevi, are also considered risk factors that warrant regular monitoring.
Diagnosis Process
Diagnosing uveal melanoma begins with a thorough eye exam where the pupil is dilated, allowing an ophthalmologist to view the back of the eye with an ophthalmoscope. This initial examination can reveal suspicious pigmented lesions. If a potential tumor is identified, specialized imaging tests are used to confirm the diagnosis and gather detailed information about the growth.
Ocular ultrasound is a primary diagnostic tool. This non-invasive test uses sound waves to create an image of the inside of the eye, allowing doctors to measure the tumor’s exact size and thickness. Other imaging techniques, such as optical coherence tomography (OCT) and fluorescein angiography, provide additional details about the tumor and its impact on surrounding structures. Unlike many other cancers, a biopsy is often not required for diagnosis, as the combination of clinical examination and imaging is highly accurate.
Treatment Approaches
The primary goal of treatment is to destroy cancer cells while preserving the patient’s vision and the eye itself when possible. Radiation therapy is the most common treatment for the primary tumor. Plaque brachytherapy is a frequent form of this treatment, involving the surgical placement of a small, radioactive disc, or plaque, on the outside of the eye directly over the tumor. The plaque delivers a concentrated dose of radiation to the melanoma over several days before being removed.
Another radiation option is proton beam therapy, which uses high-energy protons to target the tumor with precision, minimizing damage to surrounding healthy tissues. Surgical intervention is also a possibility, with the approach depending on the tumor’s size and location. For smaller tumors, a resection may be performed to remove only the tumor and a small margin of healthy tissue around it.
In cases involving very large tumors, or when the tumor has caused significant vision loss or high pressure within the eye, removal of the entire eye, a procedure known as enucleation, may be necessary. Following enucleation, a patient is typically fitted for a custom-made artificial eye that matches the appearance of the remaining eye.
Metastasis and Prognosis
The long-term outlook for uveal melanoma is influenced by factors like the tumor’s size, its location within the uvea, and its genetic makeup. For instance, tumors located in the iris tend to be slower-growing and less likely to spread than those in the choroid or ciliary body. Genetic testing of tumor cells, sometimes obtained through a fine-needle biopsy, can identify specific mutations that indicate a higher risk of the cancer spreading.
Uveal melanoma has a known tendency to spread to other parts of the body, a process called metastasis. The most common site for this metastasis is the liver. Because of this risk, patients undergo regular surveillance imaging, such as liver ultrasounds or other scans, for many years after the initial eye tumor has been treated.