Iris melanoma is a rare form of cancer that originates in the iris, the colored part of the eye. It accounts for approximately 3% to 5% of uveal melanomas, which are the most common primary intraocular malignant tumors in adults. This eye cancer is significantly less common than cutaneous melanoma, or skin cancer. Early detection is important.
Identifying Iris Melanoma
Recognizing iris melanoma often begins with noticing a visual change within the eye. A common sign is the appearance of a dark or brown spot on the iris, which may grow larger or change in its shape or pigmentation over time. The lesion can vary in color from off-white to dark brown, and may appear flat, elevated, or dome-shaped. Other indicators can include a distortion of the pupil’s shape, a noticeable difference in color between the two irises (heterochromia), or the development of glaucoma in one eye. Some individuals might also experience chronic inflammation within the eye or a spontaneous bleeding into the anterior chamber, known as hyphema.
It is important to distinguish between a benign iris nevus, commonly referred to as an eye freckle, and a potentially cancerous melanoma. Iris nevi are generally harmless pigmented spots, often appearing as small, flat smudges, whereas melanomas tend to be more solid, thicker, and may show growth. While most pigmented spots on the iris are benign nevi, any changes in their size, shape, color, or the development of associated symptoms like changes in vision or eye discomfort, warrant immediate professional examination by an eye care specialist.
Causes and Risk Factors
Several factors can increase an individual’s likelihood of developing iris melanoma. People with lighter eye colors, such as blue, green, or hazel, tend to have a higher incidence of this condition. Individuals with fair skin, red hair, or blond hair also face an elevated risk. These characteristics are associated with a lower concentration of melanin pigment, which may play a role in susceptibility.
While excessive exposure to ultraviolet (UV) light is a well-documented risk factor for skin melanoma, its link to iris melanoma is less definitively established. Nevertheless, UV exposure is still considered a potential contributing factor for eye melanomas. Genetic predispositions also play a role, with conditions like dysplastic nevus syndrome, which involves atypical moles, increasing the risk. A family history of specific genetic conditions, such as BAP1 tumor predisposition syndrome, can also elevate an individual’s susceptibility to developing iris melanoma.
The Diagnostic Process
Confirming a diagnosis of iris melanoma involves a thorough examination by an ophthalmologist or an ocular oncologist. The initial step includes a comprehensive eye exam using a slit-lamp biomicroscope, which provides a magnified view of the iris and the anterior segment. This allows the specialist to closely inspect the lesion’s characteristics, including its size, shape, and pigmentation.
Specialized diagnostic tools are then employed to gather more detailed information about the tumor. Gonioscopy is used to examine the eye’s drainage angle, helping determine if the tumor extends into this area. Ultrasound biomicroscopy (UBM), a high-frequency ultrasound imaging technique, provides detailed images of the iris and anterior segment, allowing for precise measurement of the tumor’s thickness and internal structure.
High-resolution photography is also used to create a baseline image of the lesion. Serial photography, taken over months or even years, is important as it allows doctors to document any subtle growth or changes, a significant indicator of malignancy. Due to the high accuracy of these non-invasive imaging methods and the potential risks associated with invasive procedures, an initial biopsy of an iris lesion is rarely performed.
Treatment and Management Approaches
The approach to treating iris melanoma depends on several factors, including the tumor’s size, location, and observed growth. For small, stable, or low-risk lesions, the most common strategy is observation, also known as “watchful waiting.” This involves regular monitoring with periodic photography and ultrasound examinations to detect any changes that might indicate progression.
When treatment becomes necessary, radiation therapy is a common choice. Plaque brachytherapy is a targeted radiation treatment where a small, radioactive disc, or plaque, is temporarily placed directly onto the outer surface of the eye, precisely over the tumor. This delivers a high dose of radiation to destroy cancer cells while aiming to minimize damage to surrounding healthy eye tissues, often preserving vision.
Surgical removal is another option, particularly for smaller tumors. An iridectomy involves excising a piece of the iris containing the tumor. For tumors that extend deeper or involve adjacent structures, an iridocyclectomy may be performed, which removes a portion of both the iris and the ciliary body. While effective, surgical removal of iris tissue can sometimes lead to issues like glare or astigmatism.
In rare instances, when tumors are large, have caused extensive damage to the eye, or carry a high risk of spreading, removal of the entire eye, known as enucleation, may be considered. This procedure is reserved as a last resort to prevent further complications and potential metastasis. Regardless of the initial treatment, lifelong follow-up appointments are important to monitor for any local recurrence of the melanoma within the eye or its spread to other parts of the body, most commonly the liver.