Iris Melanoma: When a Spot on the Iris Needs Attention

Noticing a brown spot on the colored part of your eye — or being told about one at an eye check — understandably raises the question of melanoma. The reassuring news is that most iris spots are harmless freckles, nevi or cysts. Iris melanoma does occur, but it is uncommon, often found while still small, and has the most favorable outlook of all melanomas inside the eye.

This page explains how specialists tell an iris nevus from iris melanoma and from an iris cyst, which features raise concern, and how iris melanoma is treated. Melanomas behind the iris are covered on the main uveal melanoma page.

What is a spot on the iris: freckle, nevus, cyst or melanoma?

Several quite different lesions can appear on or behind the iris, the front part of the uvea:

Other look-alikes include Lisch nodules (small iris spots seen in neurofibromatosis type 1), a melanocytoma (a very dark benign nevus) and metastases from cancers elsewhere, most often breast cancer, lung cancer or skin melanoma; about 8% of metastases to the uvea involve the iris.

How common are iris nevi and iris melanoma?

Iris nevi are found in fewer than 5% of people and make up about 61% of pigmented (melanocytic) iris tumors in published series. Iris melanoma is much rarer: it accounts for only about 2–5% of uveal melanomas, is most often diagnosed in the fifth decade of life (people in their 40s) and is more common in people with light-colored irises. Unlike melanomas at the back of the eye, iris melanomas carry a genetic signature of ultraviolet light damage.

Can an iris nevus turn into melanoma?

Rarely. In a study of 1,611 eyes with iris nevi seen at a specialist referral center, transformation into melanoma occurred in fewer than 1% at 1 year, 3–4% at 5 years, 8% at 15 years and 10–11% at 20 years. The risk for an ordinary nevus found at a routine eye test is likely to be lower.

Specialists use the mnemonic ABCDEF to identify nevi at higher risk of becoming melanoma:

Suspicious nevi are usually re-examined every 3–6 months at first and yearly once stable — an approach similar to that for a choroidal nevus at the back of the eye.

What are iris cysts, and can they look like melanoma?

Iris cysts are small fluid-filled sacs. The most common type, the pigment epithelial cyst, arises from the pigmented back surface of the iris and occurs mainly in adults; it looks brown-black and velvety and, from behind, can push the iris forward and mimic a solid tumor. Stromal cysts form within the front layer of the iris, are clear, are seen more often in children and can enlarge. Cysts can also follow eye surgery or injury.

Most cysts need no treatment. Occasionally they raise eye pressure or touch the cornea or lens; these can be treated with laser, by draining and sealing the cyst, or by surgical removal. The key test is ultrasound biomicroscopy: a cyst shows a thin bright wall around a dark, fluid-filled center, whereas a melanoma is solid.

What are the signs of iris melanoma?

Iris melanoma is often noticed as a new or enlarging spot, or found at a routine examination. In a series of 317 eyes, the most common findings were:

• a distorted or displaced pupil (corectopia) — 45%;
• raised eye pressure (glaucoma) — 35%;
• tumor cells seeded into the drainage angle — 28%;
• pigment turned outward at the pupil edge (ectropion uveae) — 24%;
• bleeding in the front chamber of the eye (hyphema) — 3%;
• growth outside the eye — 3%.

Iris melanomas take several forms: circumscribed (a discrete nodule, often in the lower iris), diffuse (spreading flat across the iris), ring-shaped around the drainage angle, and a rare "tapioca" form.

How is iris melanoma diagnosed?

Diagnosis rests on careful examination and on documenting change over time:

• Slit-lamp examination and standardized photographs record size, color, margins and vessels, so that growth can be measured later.
• Gonioscopy, an examination of the drainage angle through a special contact lens, shows whether the tumor has spread into the angle.
• Ultrasound biomicroscopy (UBM) measures thickness, shows whether the tumor extends into the ciliary body behind the iris, and distinguishes solid tumors from cysts.
• Anterior segment OCT gives detailed cross-sections of the iris and angle, although heavy pigment can limit how deep it sees.
• Fine-needle aspiration or incisional biopsy is used in selected cases when the diagnosis remains uncertain.

Iris melanoma has its own AJCC stage categories, based on how much of the iris is involved, whether glaucoma is present and whether the tumor extends beyond the iris — see eye cancer stages and how eye tumors are diagnosed.

How is iris melanoma treated?

Treatment is recommended once growth is documented or melanoma is clearly present; the choice depends on the tumor's size, its spread across the iris and angle, and eye pressure:

Surgery changes the shape of the pupil, and radiation near the front of the eye can cause cataract and affect the eye surface. Details are on the plaque brachytherapy and radiotherapy options pages.

What is the outlook for iris melanoma?

Iris melanoma has the most favorable prognosis of all uveal melanomas. Spread to other organs occurs in about 3% of patients at 5 years, 5% at 10 years and 10% at 20 years, and 5-year survival exceeds 95%. Because late spread and local regrowth are possible, follow-up continues for many years; see also prognosis and survival.

Assessment of iris spots in Antalya

Prof. Türkoğlu examines the iris and drainage angle, reviews earlier photographs and imaging, and explains whether a lesion looks like a freckle, nevus, cyst or possible melanoma, with a follow-up plan. Surgical removal of iris tumors is part of her ocular oncology practice; radiation treatments are planned and delivered together with radiation oncology teams. Patients abroad can send slit-lamp photographs and any UBM or OCT images for a remote second opinion.