Choroidal Melanoma, Uveal, or Choroidal Melanoma (Tumor on the Eye Originating from the Pigmented Cells of the Choroid) in Dogs

  • Occurrence: rarer
  • Location of illness: Head/Neck
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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 choroid of the eye.

The most important facts at a glance

Uveal or choroidal melanoma is a rare tumor in dogs that originates from the pigmented cells of the choroid in the eye. These cells contain melanin, which gives the eye color and protects it from harmful light. The exact causes are not fully understood, but genetic factors and possibly environmental factors such as sun exposure may play a role. Symptoms can include changes in iris color, distorted pupils, inflammatory conditions, increased intraocular pressure, and visual impairments. Thorough examinations by a veterinarian are necessary for diagnosis, often with the help of ophthalmoscopy, ultrasound, biopsy, and imaging procedures such as MRI or CT scans.

Treatment depends on the 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.

Preventive measures are limited as the causes are not fully understood. Regular veterinary examinations and possibly protection from UV radiation may help. Owners should pay attention to symptoms in order to act early.

Causes

The choroid is a 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, similar to skin cells, can degenerate and become a melanoma. In dogs, the occurrence of melanoma in the choroid is rare, but the disease can have serious consequences.

The exact causes for the development of uveal melanoma are not yet fully understood. It is believed that genetic factors may play a role, as certain dog breeds are more frequently affected. Environmental factors, such as excessive sun exposure, could also play a role, although this is less clear in dogs than in humans.

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

Symptoms

An early sign of choroidal melanoma may 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.

More advanced symptoms may include swelling of the eye, redness, pain, or irritation. The dog may start to rub or blink the affected eye. In some cases, there may be vision loss or displacement of the eyeball.

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

Diagnosis

The diagnosis of uveal melanoma requires a thorough examination by a veterinarian, ideally one who specializes in eye diseases. An ophthalmoscope can be used to inspect the inside of the eye and look for signs of a tumor.

Additional diagnostic tests may include ultrasound examinations of the eye to determine the size and exact location of the tumor. A biopsy can also be performed, in which a small sample of the tumor tissue is taken and examined microscopically to confirm the diagnosis.

Imaging procedures such as MRI or CT scans can be used to determine whether the melanoma has spread to other parts of the body.

Therapy

The treatment of choroidal melanoma depends on the size and stage of the tumor. In some cases, surgical removal of the tumor may be necessary. This may involve 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 the use of laser therapy, which specifically targets the tumor and spares 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 general 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 the tumor 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 monitor for recurrence of the tumor or its spread.

The dog’s quality of life is an important factor that must be considered when deciding on treatment. Some treatments can have significant side effects that could impair the animal’s well-being.

Prevention

Since the exact causes of choroidal melanoma are not fully understood, there are no specific preventive measures. However, general health care and regular veterinary examinations can help to detect changes in the eye early.

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

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

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