Canine Melanoma (Common in Oral and Nail Areas): Symptoms and Treatment

ImmunityDiseasesMeongsiljang Veterinary Advisory Board

Canine melanoma is a type of skin cancer caused by malignant transformation of melanocytes, most commonly occurring in the mouth and under the nails. Early detection and surgical treatment are critical factors in determining survival rates.

What is Canine Melanoma?

A veterinarian examining a puppy's mouth.

Canine melanoma is a tumor that arises from melanocytes, the cells responsible for producing pigment, and can develop not only on the skin but also on oral mucous membranes and under the nails. While many skin melanomas are benign and slow-growing, those occurring on mucous membranes or at the junction of mucous and keratinized tissues—such as in the mouth, on the lips, or on the toes—are known to be aggressive and frequently metastasize to the lymph nodes and lungs. Therefore, if you notice any new, firm, irregular lumps or bumps in your dog’s mouth or on the gums (which may be dark or light in color), do not delay; have them examined by a veterinarian. Sudden nail loss or swelling of the toes are also critical signs that should not be overlooked.

Causes and Pathogenesis: Why Does It Occur?

Melanoma is a tumor that originates from melanocytes, the pigment-producing cells found in the skin and mucous membranes. Melanocytic tumors can develop not only on the skin but also on the oral mucosa, anal sacs, and other areas. According to veterinary textbooks, the tumor's location is a critical factor in determining its nature and malignancy. Tumors arising at the junction of mucous membranes and skin, such as on the toes, lips, or eyelids, tend to be more aggressive and are more likely to metastasize to the lymph nodes, lungs, and other organs. While the exact causes are not yet fully understood, melanoma is not limited to specific breeds and can occur in any breed or mixed-breed dog. Therefore, it is important to regularly monitor your pet's mouth and toes for any changes.

Suspect Melanoma If You Notice These Symptoms

Malignant melanoma symptoms vary depending on where the tumor develops. If you notice any of the following signs, seek veterinary care immediately. - Oral melanoma: Dark or reddish masses on the gums, tongue, or roof of the mouth; bad breath; drooling; tooth loss - Nail (digital) melanoma: Sudden loss or curling of the nail; swelling of the toe; limping - Cutaneous melanoma: Dark, irregularly shaped nodules; bleeding; ulceration - Ocular melanoma: Changes in iris color; black spots inside the eye; changes in pupil shape

When to Seek Immediate Veterinary Care

Oral melanoma is an aggressive cancer with a short average survival time after diagnosis. If you notice any of the following signs, please visit a veterinary clinic within 24 hours. - Black masses or blood-tinged saliva in the mouth - Nails falling out for no apparent reason, along with swelling or discharge from the toes - Skin spots that have rapidly grown or changed in color or shape over the past 2–4 weeks - Lymph nodes (under the jaw, neck, or armpits) that feel hard and swollen

How Is Diagnosis Performed?

Diagnosing melanoma is a step-by-step process. According to veterinary textbooks, confirming the diagnosis, assessing for metastasis, and accurately staging the disease are key to developing a treatment plan. - Fine Needle Aspiration (FNA): A primary test where cells are extracted with a needle and examined under a microscope. - Biopsy: A definitive diagnosis is made through histopathological examination of representative tissue samples, which also allows for grading malignancy based on factors like mitotic count. - Imaging (X-rays, CT): Three-view thoracic radiographs are used to check for lymph node and lung metastasis, while CT and MRI scans assist in pre-surgical planning. - Blood Tests (CBC, Serum Chemistry) and Abdominal Ultrasound: These evaluate the patient's overall health and check for metastasis in organs such as the liver and spleen. Melanomas occurring at mucocutaneous junctions, such as in the mouth or on the toes, carry a higher risk of metastasis. Therefore, comprehensive staging—including fine needle aspiration of lymph nodes and thoracic radiographs—is essential.

Treatment Options — Surgery, Radiation, and Immunotherapy

Treatment is tailored to the tumor’s location, size, and whether it has metastasized. - Surgical excision: Wide surgical removal is the primary treatment. For oral melanomas, partial mandibulectomy (removal of part of the jawbone) is common, while for digital melanomas, amputation of the affected toe is typically performed. - Radiation therapy: External beam radiation (electron beam) is used as an adjunctive treatment when the tumor is in a location that makes surgery difficult or when complete surgical excision is not possible. - Chemotherapy: Chemotherapy is used as an adjunctive treatment in cases with metastasis or high-risk profiles. Metronomic chemotherapy, which combines NSAIDs with alkylating agents, may also be employed. - Immunotherapy (melanoma vaccine): Immunotherapy using a vaccine is being explored, but its efficacy has not yet been sufficiently validated. Your veterinarian will determine the specific treatment plan and dosages based on the stage of the tumor.

A veterinarian and a pet owner discussing a treatment plan for melanoma.

Home Care Points to Monitor

Daily care during treatment or post-surgical recovery significantly impacts the prognosis. - Oral care: Switch to soft wet food after surgery, and pause tooth brushing until instructed by your veterinarian. - Wound protection: After toe amputation, an Elizabethan collar and non-slip floor mats are essential. - Nutrition: Maintain weight and muscle mass with a high-protein, high-calorie diet. - Documentation: Regularly photograph any new lumps or color changes with your smartphone. - Regular follow-ups: During the first year post-treatment, check for metastasis with CT scans and chest X-rays every two to three months.

Breeds That Require Particular Caution

Melanoma can develop in any breed or mixed-breed dog, so no breed is entirely safe. That’s why regular oral and nail examinations are helpful for early detection in every dog. More thorough checks are especially recommended in the following situations: - New lumps or color changes in the mouth or on the toes - Repeated nail loss or swelling of the toes - A history of diagnosed and surgically removed tumors Since tumors are more commonly reported in middle-aged and senior dogs, be sure to request oral and toe palpation during senior wellness exams.

Reviewed by a veterinarian

Dr. Tony — Punnawat Phongkittirak

Veterinarian

A veterinarian who majored in veterinary medicine at Khon Kaen University, Thailand, and completed the IVSA program at North Carolina State University in the United States. Drawing on clinical experience at animal hospitals, he works in the pet healthcare field and is dedicated to building a digital care environment that connects pet parents with veterinarians.

Frequently Asked Questions

My dog has always had black spots in its mouth. Are they all melanomas?

Not necessarily. Pigmented spots, known as melanoplakia, are quite common on a dog's gums, lips, and tongue. The concerning signs are new, firm lumps or spots that change in shape or size rapidly. If you've noticed such changes recently, please have them evaluated with tests like a fine-needle aspiration.

If my pet’s nail fell off, should I always suspect melanoma?

Trauma or infection can also cause a nail to fall out. However, if only one toe repeatedly loses its nail, or if the toe itself becomes swollen and changes color, it could be a tumor (such as melanoma) on the toe. Toe tumors can be aggressive, so it’s best to confirm with an X-ray and a biopsy.

What is the recurrence rate after surgery?

Oral melanoma has a high risk of metastasis and recurrence, even with wide surgical excision. Therefore, adjuvant therapies such as radiation or immunotherapy (vaccines) are often considered postoperatively, but the efficacy of vaccine-based immunotherapy remains insufficiently validated. The prognosis varies significantly depending on the stage and location of the tumor.

What kind of treatment is the melanoma vaccine (Oncept)?

This is a vaccine being studied as an immunotherapy to stimulate a dog’s immune system to attack melanoma cells. It is sometimes used as an adjuvant treatment after surgery, but its efficacy has not yet been fully evaluated. Your veterinarian will determine whether it is appropriate for your dog and establish the vaccination schedule.

Is there a way to prevent it?

The exact cause of melanoma remains unknown, so there is no definitive way to prevent it. However, the most important step is early detection: look for any new lumps or changes in pigmentation in the mouth or on the toes, especially during regular oral check-ups. Since melanoma can occur in any breed, developing a habit of regularly feeling and observing your pet’s body can be very helpful.

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References

[1] Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition, Chapter on Melanoma

[2] BSAVA Manual of Canine and Feline Oncology, 3rd Edition

[3] Bergman PJ et al., Long-term survival of dogs with advanced malignant melanoma after DNA vaccination with xenogeneic human tyrosinase, Clin Cancer Res, 2003