Tumor of the eye originating from the pigmented cells of the choroid in dogs (choroidal melanoma, uveal or choroidal melanoma)

  • Occurrence: rarer
  • Location of disease: Head/Neck
Author: Dr. med. vet. Gisa Löwe | Last modified: 10.08.2026
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When to visit the vet?

Non-urgent see a veterinarian within 2–3 days

?

If the condition worsens / symptoms persist, consult a veterinarian.

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Definition

A choroidal melanoma, also known as uveal or choroidal melanoma, is a rare but potentially malignant tumor that occurs in dogs and develops from the pigmented cells of the eye’s choroid.

The most important facts at a glance

Uveal or choroidal melanoma is a rare tumor in dogs that arises from the pigmented cells of the choroid in the eye. These cells contain melanin, which gives the eye color and protects against harmful light. The exact causes are not fully understood; however, genetic and environmental factors, including sun exposure, could play a role. Symptoms can include changes in iris color, distorted pupils, inflammatory conditions, increased intraocular pressure, and vision impairment. For diagnosis, thorough examinations by a veterinarian are necessary, often using ophthalmoscopy, ultrasound, biopsy, and imaging techniques such as MRI or CT.

Treatment depends on tumor size and stage and may include surgical removal, radiation therapy, or laser therapy. In advanced cases, chemotherapy may be necessary. The prognosis varies depending on the tumor stage and whether metastases are present. With early diagnosis and treatment, the prognosis is more favorable. Regular follow-up examinations are important to monitor for recurrence or spread of the tumor.

Prevention measures are limited as the causes are not fully understood. Regular veterinary check-ups and, if necessary, protection from UV radiation could help. Owners should watch for symptoms to be able to act early.

Causes

The choroid is part of the middle layer of the eye, known as the uvea. It consists of pigmented cells that contain melanin, which gives the eye its color and protects the inside of the eye from harmful light. However, these cells can become abnormal, similar to skin cells, and develop into a melanoma. In dogs, melanoma in the choroid is rare, but the condition can have serious consequences.

The exact causes of uveal melanoma are not yet fully understood. Genetic factors are thought to play a role, as certain dog breeds are affected more often. Environmental factors, such as excessive sun exposure, may also play a role, although this is less clear in dogs than in humans.

Mutations in cells play a crucial role in the development of melanoma. These genetic changes can occur spontaneously or be caused by external influences. Research is investigating whether certain genes or genetic markers are associated with an increased risk of this type of tumor in dogs.

Symptoms

Rare symptoms:

An early sign of choroidal melanoma can be a change in eye color or the appearance of dark spots on the iris. These changes are often subtle and can be easily overlooked.

Advanced symptoms may include swelling of the eye, redness, pain, or irritation. The dog might start rubbing the affected eye or squinting. In some cases, vision loss or displacement of the eyeball may occur.

Because these symptoms can also occur with other eye diseases, it’s important to seek a veterinary examination if choroidal melanoma is suspected.

Therapy

Treatment for choroidal melanoma depends on the size and stage of the tumor. In some cases, surgical removal of the tumor may be necessary. This may include enucleation (removal of the eye), especially if the tumor is very large or vision has already been irreversibly damaged.

Radiation therapy can be used for smaller tumors to destroy the cancer cells without having to remove the eye. A newer option is laser therapy, which targets the tumor while sparing the surrounding healthy tissue.

In some cases, chemotherapy may be considered, especially if the tumor has metastasized. The choice of treatment depends on many factors, including the dog’s overall health and the owner’s preferences.

Prognosis and follow-up care

The prognosis for a dog with choroidal melanoma depends on various factors, including the size and location of the tumor, whether it has spread, and how early it was diagnosed. With early diagnosis and treatment, the prognosis can be positive, especially if the tumor has not yet metastasized.

However, if the tumor has spread to other parts of the body, the prognosis worsens significantly. Regular follow-up examinations are important to detect a recurrence of the tumor or its spread.

The dog’s quality of life is an important factor to consider when deciding on treatment. Some treatments can have significant side effects that affect the animal’s well-being.

Prevention

Since the exact causes of choroidal melanoma are not fully understood, there are no specific prevention measures. However, general health care and regular veterinary check-ups can help detect changes at an early stage.

For dogs that spend a lot of time outdoors, protecting the eyes from excessive UV radiation may be useful, although the prevention of eye tumors in dogs is less researched. Dog sunglasses or avoiding intense sunlight could theoretically reduce the risk.

Educating owners about possible signs of choroidal melanoma is also important so they can act quickly at the first sign of changes.

Outlook on current research

Choroidal melanoma belongs to the uveal melanomas and is the most common primary malignant tumor of the eye in adults. The main problem today is less about local control in the eye than the risk of later metastases, especially in the liver. This is precisely why current research focuses heavily on which tumors are biologically particularly dangerous, even if they initially appear small. (eyewiki.org, pubmed.ncbi.nlm.nih.gov)

A central field of research is molecular risk classification. Certain genetic changes, such as in BAP1, SF3B1, or EIF1AX, help to more accurately estimate the risk of metastasis. In addition, gene expression profiles and increasingly liquid biopsies—tumor information from blood samples—are being investigated. The goal is to identify high-risk patients earlier and to manage follow-up care more specifically. (pubmed.ncbi.nlm.nih.gov, nature.com)

Therapeutically, the outlook is, cautiously speaking, better than just a few years ago. For locally limited tumors, radiation therapy and other eye-preserving procedures are established; for metastatic disease, progress was minimal for a long time. In the meantime, Tebentafusp has brought important progress for some patients with metastatic uveal melanoma. At the same time, studies are underway on combination therapies, new immunotherapies, and targeted approaches against central signaling pathways of the tumor. (fda.gov, nature.com)

Overall, research is clearly moving toward personalized ocular oncology with better prognosis assessment and more targeted systemic therapy.

Frequently Asked Questions (FAQs)

1. What is a choroidal melanoma in dogs?
Choroidal melanoma (uveal melanoma) is a tumor that originates from the pigmented cells of the choroid, the iris, or the ciliary body. It is the most common primary eye tumor in dogs. The tumor usually grows slowly and, unlike in humans, often has a benign character in dogs.
2. What symptoms are noticeable?
Typical signs are dark spots or nodules on the iris that grow larger over weeks to months. Other signs can include an irregular pupil shape, changes in eye color, secondary glaucoma, uveitis, or a protrusion of the eyeball. Occasionally, owners also notice lens displacement or bleeding in the eye.
3. Which dogs are more commonly affected?
Middle-aged to older dogs are predisposed, especially Labrador Retrievers, Golden Retrievers, and German Shepherds. There is no clear gender preference. The tumor is rare in younger dogs, but it does occur.
4. How is the diagnosis made?
Ophthalmological examination with a slit lamp and ophthalmoscopy often shows the tumor directly. To assess the extent, eye ultrasound (B-scan) and, if necessary, MRI or CT are used. A definitive diagnosis is ultimately achieved through histology, usually after enucleation of the eye.
5. Is uveal melanoma malignant?
In dogs, the majority of uveal melanomas are benign or low-grade malignant. Metastases are rare and most commonly affect the liver. Crucial for the prognosis are the mitotic rate, location (ciliary body is more aggressive than the iris), and spread beyond the ocular tunics.
6. How is the disease treated?
Small, superficial iris tumors can be treated using laser photocoagulation or local resection without sacrificing the eye. For advanced tumors, secondary glaucoma, or rapid growth, enucleation (removal of the eyeball) is the treatment of choice. Adjuvant chemotherapy is only necessary for rare aggressive forms.
7. Does the dog lose much quality of life after enucleation?
Dogs usually compensate for the loss of an eye very well and only need a few weeks to adjust. Their vision on the remaining side and their other senses are very well developed for this. Quality of life is generally maintained.
8. How high is the risk of metastasis?
In studies, around 5% of uveal melanomas in dogs metastasize, especially those with a higher mitotic rate or extraocular spread. Regular follow-up with abdominal ultrasound and X-ray of the thorax every six months for two years is recommended.
9. Can a choroidal melanoma spontaneously stop growing?
Very small iris melanomas occasionally do not grow further for years. As long as they remain small, cause no pain, and do not impair vision, close observation with regular checks is justifiable. As soon as they grow, intervention is indicated.
10. How does choroidal melanoma differ from eyelid melanoma?
Choroidal melanomas originate from structures inside the eye and are predominantly benign in dogs. Eyelid melanomas are located on the eyelid skin and are also usually benign. Oral and digital melanomas in dogs, on the other hand, are highly malignant and frequently metastasize; their prognosis is significantly worse.

Literature

  • Badanes, Z., Espinheira Gomes, F., & Ledbetter, E. C. (2020). Choroidal melanocytic tumors in dogs: A retrospective study. Veterinary Ophthalmology, 23(6), 987–993. https://doi.org/10.1111/vop.12839
  • Moreira, M. V. L., Langohr, I. M., Campos, M. R. de A., Ferreira, E., Carvalho, B., Blume, G. R., Montiani-Ferreira, F., & Ecco, R. (2022). Canine and feline uveal melanocytic tumours: Histologic and immunohistochemical characteristics of 32 cases. Veterinary Medicine and Science, 8(3), 1036–1048. https://doi.org/10.1002/vms3.752
  • Guerra Guimarães, T., Menezes Cardoso, K., Tralhão, P., Marto, C. M., Alexandre, N., Botelho, M. F., & Laranjo, M. (2021). Current therapeutics and future perspectives to ocular melanocytic neoplasms in dogs and cats. Bioengineering, 8(12), Article 225. https://doi.org/10.3390/bioengineering8120225
  • Giuliano, E. A., Chappell, R., Fischer, B., & Dubielzig, R. R. (1999). A matched observational study of canine survival with primary intraocular melanocytic neoplasia. Veterinary Ophthalmology, 2(3), 185–190. https://doi.org/10.1046/j.1463-5224.1999.00080.x
  • Dubielzig, R. R., Aguirre, G. D., Gross, S. L., & Diters, R. W. (1985). Choroidal melanomas in dogs. Veterinary Pathology, 22(6), 582–585. https://doi.org/10.1177/030098588502200612
  • Wilcock, B. P., & Peiffer, R. L. (1986). Morphology and behavior of primary ocular melanomas in 91 dogs. Veterinary Pathology, 23(4), 418–424. https://doi.org/10.1177/030098588602300411
  • Polton, G., Borrego, J. F., Clemente-Vicario, F., Clifford, C. A., Jagielski, D., Kessler, M., Kobayashi, T., Lanore, D., Queiroga, F. L., Rowe, A. T., Vajdovich, P., & Bergman, P. J. (2024). Melanoma of the dog and cat: Consensus and guidelines. Frontiers in Veterinary Science, 11, Article 1359426. https://doi.org/10.3389/fvets.2024.1359426