Ocular Oncology · Patient Series
“You have a freckle
at the back of your eye.”
Here is what that means.
A choroidal nevus is one of the most common things an eye doctor finds on a routine dilated exam, and almost all of them stay harmless for life. A very small number turn into choroidal melanoma, the most common primary eye cancer in adults. This guide covers how specialists tell the two apart, the six features that make them look more closely, and how melanoma is treated today, often without removing the eye.
malignant (estimate)
million adults/yr (US)
(TFSOM-DIM)
Section 01 — Nevus or Melanoma
A mole you
can’t see in a mirror.
Behind the retina sits the choroid, a thin, dark layer packed with blood vessels that feeds the outer retina. Like skin, it contains pigment cells called melanocytes. When a cluster of them forms a flat, slate-grey patch, it is a choroidal nevus: an eye freckle. Population studies in white adults find one in several percent of people. They are seen less often in people of Asian or African ancestry.
The choroid is one part of the uvea. The other two parts are the iris, the coloured ring at the front, and the ciliary body behind it. Melanoma can start in any of the three. Choroidal tumours make up the large majority, roughly nine in ten. Uveal melanoma is uncommon. US registry data put it at around 5 new cases per million adults per year, and it is rarer still in darker-skinned populations. Even so, it is the most common cancer that starts inside the adult eye.
A choroidal nevus is a benign pigmented spot under the retina, found on a routine dilated exam and usually causing no symptoms. Most never change. A widely cited estimate puts the risk of a nevus becoming melanoma at about 1 in 8,800 per year. Doctors decide how closely to watch one by checking six features: thickness over 2 mm, subretinal fluid, symptoms, orange pigment, hollowness on ultrasound, and diameter over 5 mm. Lesions with several of these need specialist review. Choroidal melanoma is usually treated with plaque or proton radiation, and that often saves the eye. Removing the eye is reserved for selected cases. Lifelong monitoring matters because the cancer can spread to the liver.
Section 02 — Interactive
Six features that
make a specialist
look closer.
In 2019 the Wills Eye Hospital ocular oncology group published risk factors from more than 2,000 nevi followed over time. They summarised them as TFSOM-DIM, short for “To Find Small Ocular Melanoma Doing IMaging”. Adjust the lesion and toggle the features below to see how they add up.
In that series, a nevus with none of the features had a very low chance of growing over five years. Each added feature raised the risk, and lesions with three or more grew in a large share of cases. The features are not a score to work out at home. Each one needs a specific test. Thickness and hollowness are measured with B-scan ultrasound, fluid with OCT, orange pigment with autofluorescence photography, and diameter on wide-field photographs.
Section 03 — Symptoms & Diagnosis
Silent at first,
then shadows and flashes.
Many choroidal melanomas cause no symptoms and are found on a routine exam. When symptoms do appear, they depend on where the tumour is and whether it is leaking fluid under the retina. They include blurred or distorted vision, flashes of light, new floaters, or a shadow in part of the visual field. These same symptoms are far more often caused by harmless vitreous changes or by retinal tears, but any new flashes or shadow should be checked promptly.
| Test | What it shows |
|---|---|
| Dilated exam & wide-field photos | Colour, diameter, margins and surface features; the baseline for comparing future visits |
| B-scan ultrasound | Thickness, internal “hollowness” (low reflectivity), and the collar-button or mushroom shape typical of melanoma |
| OCT | Subretinal fluid and changes in the retina over the lesion, even when very subtle |
| Autofluorescence | Orange pigment (lipofuscin) glows brightly, a known risk feature |
| Biopsy (selected cases) | Rarely needed for diagnosis. Increasingly used to obtain tumour genetics for prognosis. |
Diagnosis is usually clinical. In the large Collaborative Ocular Melanoma Study (COMS), the clinical diagnosis was confirmed by pathology in more than 99 percent of eyes that were removed. Specialists also have to rule out look-alikes: a choroidal haemangioma, a metastasis from cancer elsewhere, bleeding under the retina from macular degeneration, and congenital hypertrophy of the retinal pigment epithelium (CHRPE).
Section 04 — Treatment
Saving the eye
without trading away survival.
For much of the twentieth century, removing the eye (enucleation) was the standard treatment. The COMS randomised trial asked whether radiation could do as well for medium-sized tumours. It randomised patients to iodine-125 plaque brachytherapy, in which a small radioactive disc is stitched to the outside of the eye for a few days, or to enucleation.
Rounded figures from COMS report no. 28 (Arch Ophthalmol 2006). The difference was not statistically significant. All-cause mortality includes deaths unrelated to melanoma in an older population. See References.
The answer was clear: no meaningful survival difference. A companion COMS trial in large tumours found that radiation given before enucleation did not improve survival either. Today, the choice depends mainly on tumour size, location and how much vision the eye can keep.
Section 05 — Genetics & Prognosis
Why the eye
is only half the story.
The most serious risk with uveal melanoma is spread through the bloodstream, mainly to the liver. It can happen even after the eye tumour is fully controlled, because tiny deposits may already have spread before treatment. In a Finnish cohort followed for up to 35 years, around half of patients eventually died of metastatic melanoma.
Tumour genetics now help separate patients by risk. Nearly all uveal melanomas carry an early mutation in GNAQ or GNA11, which is different from the BRAF-driven pattern common in skin melanoma. Loss of one copy of chromosome 3 (monosomy 3), and inactivation of the BAP1 gene that sits on it, mark the tumours most likely to spread. Gene-expression tests sort tumours into a lower-risk class 1 and a higher-risk class 2. People at higher risk usually have liver imaging at regular intervals.
Phase 3 trial in previously untreated HLA-A*02:01-positive patients (Nathan et al., NEJM 2021). The US FDA approved tebentafusp for this group in January 2022.
For decades, metastatic uveal melanoma had no therapy proven to extend life. Tebentafusp, a bispecific protein that directs T cells to the tumour, changed that for patients with the HLA-A*02:01 tissue type, which a blood test can identify. Liver-directed treatments and clinical trials are options for others. The progress is real, but this is still a serious disease, and that is why early detection of growing lesions matters.
start in the choroid (approx.)
confirmed by pathology
for metastatic disease
Section 06 — Who Is at Risk & What to Do
If you’ve been told
you have a nevus.
Uveal melanoma is most often diagnosed around age 60. Risk factors include fair skin, light-coloured eyes, ocular melanocytosis (a congenital excess of pigment in and around the eye), and, rarely, an inherited BAP1 tumour predisposition syndrome. Most people with a nevus have none of these, and most will never have a problem.
| Situation | Typical approach |
|---|---|
| Flat, small nevus, no risk features | Baseline photographs, then a recheck, often at 6 to 12 months and yearly after that if stable |
| One or two risk features | Closer imaging follow-up, often with ultrasound and OCT; referral to an ocular oncologist is common |
| Several features, or documented growth | Specialist assessment; may be managed as a small melanoma |
| New flashes, floaters, shadow or blur | Prompt eye examination, whether or not a nevus is known |
A 58-year-old woman with blue eyes has a retinal photo during a routine eye test. It shows a grey patch beside the macula. She has no symptoms. Ultrasound measures it at 2.4 mm thick and 6 mm across, and OCT shows a thin rim of fluid. That gives three features: thickness, diameter and fluid. She is referred to an ocular oncologist, who documents growth at a short-interval recheck and diagnoses a small choroidal melanoma. She is treated with plaque brachytherapy. A biopsy taken at surgery shows a lower-risk genetic profile, and she continues with periodic eye and liver checks.
The practical message is simple. A nevus is not a diagnosis to worry about, but it is one to keep track of. Go to your follow-up appointments, keep copies of your retinal photos if you can, and report new visual symptoms rather than waiting for the next scheduled visit.
Section 07 — FAQ
Frequently asked questions
about eye freckles and melanoma.
No. A choroidal nevus is a benign collection of pigment cells in the choroid, the blood-vessel layer under the retina, much like a freckle or mole on the skin. Most never change and never affect vision. A small number can grow into choroidal melanoma, which is why an eye doctor will usually photograph a nevus and check it again over time rather than ignore it.
Rarely. A widely cited estimate from US population data put the risk at roughly 1 in 8,800 nevi per year. The risk is not the same for every nevus, though. Lesions that are thicker, wider, leaking fluid, carrying orange pigment or causing symptoms are much more likely to grow, and those are the ones that get closer follow-up.
Ocular oncologists use the mnemonic TFSOM-DIM, from a large Wills Eye Hospital series: Thickness over 2 mm, subretinal Fluid, Symptoms such as blurred vision, Orange pigment, Melanoma-like hollowness on ultrasound, and DIaMeter over 5 mm. The more of these features a lesion has, the higher the chance it will grow. Imaging such as photographs, ultrasound and OCT is used to check each one.
Often, yes. Most small and medium tumours are treated with radiation, either a small radioactive plaque stitched to the outside of the eye for a few days or proton beam therapy. In the Collaborative Ocular Melanoma Study, survival after plaque radiation for medium tumours was similar to survival after removal of the eye. Removal (enucleation) is still the right choice for some large tumours or eyes that have already lost useful vision.
It can. The liver is by far the most common site. Over long follow-up, close to half of patients in some series eventually develop metastases, sometimes many years after the eye was treated. Genetic testing of the tumour helps estimate individual risk, and people at higher risk usually have regular liver scans. Tebentafusp, approved by the US FDA in 2022, was the first drug shown in a randomised trial to improve survival in metastatic uveal melanoma for patients with a specific tissue type (HLA-A*02:01).
The link with sunlight is much weaker and less consistent than it is for skin melanoma, and the main genetic changes in uveal melanoma are different from those in sun-related skin cancers. Fair skin, light eye colour and a congenital pigment condition called ocular melanocytosis are better-established risk factors. Sunglasses are sensible for other eye reasons, but the most useful protective step is a regular dilated eye examination, especially if you have been told you have a nevus.
References & Evidence Base
Peer-reviewed
citations.
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