Melanomas In Dogs: Types, Treatment & Prognosis

Melanoma is the relatively most common oral malignancy in dogs that develops from melanocytes (pigment-producing cells). The unregulated proliferation of melanocytes can develop in many locations on the body and the biological behavior of this tumor can vary tremendously with the location.

Approximately, 75% of melanomas in dogs are diagnosed in the oral cavity. Oral melanomas are considered aggressive tumors and typically exhibit a high rate of metastasis to local lymph nodes and the lungs. On average, the majority of dogs with oral melanomas will go on to develop metastatic disease even with complete removal of the local oral tumor. Melanoma should be properly differentiated from other malignant tumors of the oral cavity (e.g., fibrosarcoma, squamous cell carcinoma).

They are usually seen in older dogs (of more than10 years) and small breeds.

Melanomas are typically single tumors, but they can be rather infiltrative and tend to spread readily to distant tissues (metastasis). Melanomas are pigmented and will exhibit dark pigmentation, mixed coloring, or pink. Moreover, melanoma comes in various sizes as some will look like a plaque, or flat lesion and some will present as a distinct mass.

There are different types of melanoma and symptoms depends on the site it affects.

1. Oral Melanoma:

• Increased salivation
• Facial swelling
• Dysphagia
• Weight loss
• Halitosis
• Bleeding from the oral cavity
• Pain
• Inability to eat/ Dropping food from the mouth
• Loose teeth

2. Cutaneous Melanoma:

• Firm, round, slightly lifted, and darker speckles.
• They occur most often on the head, back, or toes.
• Lesions= 1/4″ to 2″ in diameter.
• May be painful , itching.
• Coloration can vary from brown, black, red or gray.

3. Ocular (Eye) Melanomas:

• A dark-colored flashes or specks or floaters in the eye or eyelid.
• Eye redness
• Darkening of the iris.
• Cloudy/ hazy eyes
• Twitching muscles around the eyes.
• Swelling in or around your dog’s eye.

4. Subungual (Nail Bed) Melanoma:

• Brown or black streaks in the nail.
• Bruise on nail that doesn’t heal.
• Skin darkening next to nail.
• Bleeding, discharge or swelling of the affected toe.
• Limping
• Chewing or Licking at the affected area.

The symptoms that melanoma has metastasized other areas such as lungs or liver may include:

• Vomiting
• Coughing
• Swelling of the abdomen with fluid.
• Lethargy
• Weakness
• Decreased appetite

Treatment protocol for canine melanoma is directed towards controlling the local tumor and tackling the concern for metastasis.

When your dog is diagnosed with melanoma your vet may recommend surgery, chemotherapy, radiation or a combination of these treatments.

For local control, the most common options implemented are surgery and/or radiation therapy.

Melanomas are often resistant to chemotherapy, and there are typically no durable responses.

However, Chemotherapy is usually set aside as a rescue choice for tumors that have started to metastasize or recurred.

The full surgical removal of the tumor is typically not possible due to the location of some tumors.

Nevertheless, it's important for pet owners to understand that the tumour will relapse after some time.

Follow the appropriate monitoring schedule for your pet given by the medical oncologist, as recommendations may vary for each individual.

As with any disease, the prognosis is dependent on the extent of the disease, its location, and the treatment chosen.

Discuss home treatments with your vet to ensure they’re won’t mess with other medications.

Recently the canine melanoma vaccine developed by Merial (Oncept) is available. The vaccine works best locally-controlled oral malignant melanomas.

Vaccination Schedule: One dose /two weeks and a total of four doses.

Every six months - 1 booster dose.

The vaccine can be used alone or in combination with surgery or radiation for dogs with stage II or stage III canine oral melanoma.

Doberman Pinscher, Springer Spaniel, Cocker Spaniel, Airedale Terrier, Boston Terrier, Scottish Terrier, Miniature Poodle, Chow Chow, Golden Retriever, Senior Dogs

Types:

1. Oral Melanoma:

On average, 80% of melanomas we see in dogs will be diagnosed in the oral cavity (including gingiva, tongue, hard or soft palate, and lip).

2. Nail Bed Melanoma:

A nail bed or subungual crest is the second most common location of melanoma. They represent almost 25% of digital (toe) tumors in dogs and occur mostly as a solitary lesions.

3. Dermal Melanoma:

This subtype of melanoma is confined to the epidermis, dermis, and/or hypodermis (subcutaneous) fat. This is a newly described variant of melanoma and may be single or multiple.

4. Ocular Melanoma:

Melanocytic tumors are a rare form of tumor that affects the dog’s eye as conjunctival masses, eyelids, uveal tumors, and limbal melanocytomas.

Risk Factors:

• Excessive ultraviolet (UV) light exposure.
• History of sunburn.
• Dogs at a higher elevation or living closer to the equator.
• Comes from a susceptible breed of melanoma.
• Dogs with Weakened immune systems.

Morbidity:

Melanoma Stages:

• Stage 0: Melanoma in situ- Melanoma in the epidermis.
• Stage I: Initial, low-risk primary melanoma (<2 cm diameter) with no metastasis. Prognosis is good with surgery.
• Stage II: 2 to 4 cm diameter, higher risk of recurrence, no evidence of metastasis.
• Stage III: >4 cm diameter and/or positive nodes, spread to nearby lymph nodes or nearby skin.
• Stage IV: Any size, distant metastasis present, spread to the skin or distant lymph nodes, or has spread to internal organs.

Diagnosis:

• Blood tests
• CT scan lymphangiography
• MRI scan
• PET scan
• Sentinel lymph Node Biopsy

Mortality:

Oral melanoma stage III disease - dogs treated with surgery has a median survival time of not more than 15 months.

Prognosis:

Response and prognosis are in direct correlation to the extent of the spread. Melanoma's long-term prognosis is guarded as treatment depends on the location it is developed, but it is usually manageable.

Sadly, most dogs fail to respond to treatment. These are the cases of euthanasia if their quality of life is affected.

Remissions may occur and this is completely dependent on metastasis and the severity of the disease.

Emergency - Immediate Veterinary Assistance Needed:

• Sudden Collapse
• Difficulty Breathing
• Profuse Bleeding - Internal or external

Anti Melanoma Diet:

• Reduce the carb intake of your dog.
• Foods that are often high on their lists for cancer-fighting properties are Organic, high-protein, and cruciferous foods.
• Generally, all ingredients should be fresh, easily digested, highly palatable with a good smell, and should be highly bioavailable.

The ratio would be:

35 to 50 percent protein + less than 25 percent carbs + 25 to 35 percent fat (including omega-3 fatty acids and arginine).

Some of the most popular include:

• Dark-green vegetables like spinach.
• Cruciferous vegetables, such as broccoli, cauliflower, and kale.
• Fresh, organic meats, either raw or cooked, Eggs.
• Antioxidant berries.
• Omega 3 fatty acid foods (Sardines, Mackerel, Herring, etc).

For dogs with melanoma, the long-term prognosis is generally poor, regardless of treatment. Dogs can have an improved quality of life for a period of time with proper treatment.

Usually, dogs with melanoma may live 3 months without treatment, and the median survival time improves to 5-36 months with treatment (surgery).