Melanoma in Dogs: A 2026 Guide to Treatment Options.

What is melanoma in dogs?

Melanoma is a cancer of melanocytes, the pigment-producing cells that give skin, hair, and mucous membranes their colour. When those cells turn cancerous, they form tumours that are often (but not always) darkly pigmented. In dogs, melanoma is fairly common, and unlike in people, sun exposure is not thought to be the main driver.

The most important thing to understand about canine melanoma is that its behaviour depends almost entirely on where it grows. The word "melanoma" alone tells you very little. A melanoma on the haired skin of the back is frequently benign and cured by surgery. A melanoma in the mouth is one of the more aggressive cancers in veterinary oncology, with a strong tendency to spread. Same cell type, completely different disease.

Certain breeds are over-represented, including Scottish Terriers, Cocker Spaniels, Miniature and Standard Poodles, Chow Chows, Golden Retrievers, Dachshunds, and other breeds with heavily pigmented skin and oral tissue. Most affected dogs are middle-aged or older.

Why location matters: oral, digital, skin, and eye

Veterinary oncologists group canine melanoma mainly by site, because site is the single best predictor of how it will behave.

Oral melanoma

The mouth is the most common location for malignant melanoma in dogs, and oral melanoma is the most common malignant oral tumour overall. It typically appears on the gums, lips, palate, or tongue as a pigmented (or sometimes non-pigmented) mass that may bleed, smell, or interfere with eating. Oral melanoma is locally invasive and metastasises readily, most often to the regional lymph nodes and the lungs. This is the form that demands aggressive, well-coordinated treatment.

Digital (nail bed) melanoma

Melanoma of the toe, also called subungual or digital melanoma, usually shows up as a swollen toe, a lost or deformed nail, or a non-healing sore that owners and even vets sometimes first mistake for an infection. Digital melanoma is generally malignant and carries an intermediate-to-guarded prognosis, with metastasis to lymph nodes and lungs possible.

Cutaneous (haired skin) melanoma

Melanomas arising on the haired skin are usually well-behaved. The majority are benign or low-grade, and complete surgical removal is often curative. The mitotic index, meaning how many tumour cells are actively dividing, is an important clue here: low-mitotic-index skin melanomas tend to behave benignly, while the minority with high mitotic activity can act more like their oral counterparts.

Ocular and mucocutaneous melanoma

Melanoma can also arise in the eye (often treated by removal of the eye when it threatens vision or comfort) and at mucocutaneous junctions such as the lips and eyelids. Behaviour varies, and your oncologist will weigh location, size, and biopsy findings together.

How vets diagnose melanoma

Diagnosis often begins with a fine needle aspirate (FNA), where a small needle samples cells from the mass for examination under a microscope. When the tumour is pigmented, the dark melanin granules can make the diagnosis relatively straightforward.

The complication is amelanotic melanoma, meaning tumours that produce little or no visible pigment. These can be very difficult to identify on cytology alone and are sometimes mistaken for other cancers. To confirm the diagnosis, a pathologist examines a tissue biopsy and, when needed, runs immunohistochemistry using melanocytic markers such as Melan-A, PNL2, and others. This confirms the cells are truly melanocytic even when pigment is absent.

Because oral and digital melanoma spread, staging is an important part of the work-up:

• Regional lymph node sampling: aspirating the nearby lymph nodes (mandibular nodes for oral tumours), since melanoma can spread to nodes that feel normal.
• Chest imaging: thoracic radiographs or, increasingly, a CT scan to look for spread to the lungs.
• Abdominal ultrasound in some cases, plus bloodwork and urinalysis before chemotherapy.

Staging and prognosis

For oral melanoma, oncologists commonly use a World Health Organization staging scheme based largely on tumour size: Stage I is a tumour under 2 cm, Stage II is 2 to 4 cm, Stage III is over 4 cm or with lymph node involvement, and Stage IV is distant metastasis. Larger tumours, lymph node spread, and a high mitotic index all worsen the outlook.

Prognosis tracks closely with stage and location. With surgery alone, reported median survival times for oral melanoma fall roughly with advancing stage: longer for small, completely removed Stage I tumours and considerably shorter for large or metastatic disease. Cutaneous melanomas with a low mitotic index, by contrast, are frequently cured by complete excision. These are population averages, not predictions for an individual dog. Your oncologist's estimate, based on your dog's specific tumour, is what matters.

The central challenge with oral and digital melanoma is the same one human melanoma oncologists face: local control is achievable, but distant spread is what limits survival. That is exactly why immune-based therapies have become such an active area for this cancer.

Treatment: surgery

Surgery is the foundation of treatment for most melanomas, and the goal is wide, complete removal. For cutaneous tumours this is often straightforward and may be curative on its own.

For oral melanoma, achieving clean margins frequently requires removing part of the jaw, either a mandibulectomy (lower jaw) or a maxillectomy (upper jaw). These operations sound daunting, but dogs generally tolerate them remarkably well and most eat and drink comfortably within days. For digital melanoma, the standard is amputation of the affected toe, which provides good local control with minimal effect on a dog's mobility.

Surgery controls the local tumour. What it does not do is address cancer cells that may already have travelled elsewhere, which is why oral and digital melanoma are usually treated with surgery plus something else.

Treatment: radiation

Melanoma is relatively radioresponsive, and radiation therapy plays a major role when surgery can't fully remove the tumour or when the location makes aggressive surgery impractical. Hypofractionated (coarsely fractionated) protocols, which use a handful of larger radiation doses rather than many small ones, are commonly used and can produce good local control with fewer anaesthetic events than definitive daily protocols.

Radiation is frequently combined with other treatments: it handles the local and regional disease while systemic therapy or immunotherapy targets the risk of spread. As with any radiation, it requires referral to a facility with the right equipment, and your oncologist will weigh the schedule, cost, and expected benefit for your dog.

Treatment: chemotherapy

Melanoma is, frustratingly, relatively resistant to conventional chemotherapy. There is no chemotherapy protocol that reliably extends survival in canine oral melanoma the way chemotherapy does for some other cancers.

Carboplatin is the agent most often reached for in cases of measurable or metastatic disease, and it does produce responses in a minority of dogs, but these responses tend not to be durable. Because of this limited benefit, the field has put much of its energy into immunotherapy instead, which is where melanoma has historically led veterinary oncology.

The ONCEPT melanoma vaccine

Here is a piece of history many owners don't know: the first therapeutic cancer vaccine licensed for use in any species, human or animal, was a canine melanoma vaccine. ONCEPT, originally developed by Merial (now Boehringer Ingelheim), received a USDA conditional licence in 2007 and full licensure in 2010.

ONCEPT is a xenogeneic DNA vaccine. It delivers the gene for human tyrosinase, an enzyme melanocytes use to make pigment. Because the human version is just different enough from the canine version, it nudges the dog's immune system into responding to tyrosinase, and that response can cross-react with the dog's own melanoma cells. It's given by a transdermal device as a series of injections, and it's indicated for dogs with stage II or III oral melanoma in which local disease has already been controlled by surgery or radiation.

ONCEPT was an important milestone, and many oncologists use it. It's worth being honest about the evidence, though: studies have produced mixed results. Some case series reported encouraging survival times compared with historical controls, while a later controlled study found no statistically significant survival benefit. The reasonable summary in 2026 is that ONCEPT is a reasonable, low-toxicity option whose magnitude of benefit remains debated.

What's new: personalized mRNA cancer vaccines

The most significant shift in cancer therapy this decade is the move toward personalized neoantigen vaccines, and melanoma is the disease where the human evidence is strongest. Moderna and Merck's mRNA-4157, given alongside the immunotherapy drug Keytruda, lowered the risk of melanoma recurrence or death by about 44 percent in a randomised phase 2b trial in people. BioNTech is running similar programmes. Melanoma, in other words, is the proving ground for this entire approach.

The idea is different from ONCEPT in a fundamental way. Every tumour accumulates mutations that produce neoantigens, fragments of protein that exist only on the cancer cells and nowhere in healthy tissue. Sequencing the tumour reveals those mutations; bioinformatics predicts which neoantigens the immune system can actually "see"; and an mRNA vaccine is designed to train the immune system against them. The result is genuinely personalised. A vaccine built from one patient's tumour is only useful for that patient.

The same pipeline works in dogs. The species reference is different (the canine genome), the immune-presentation molecules are different (DLA rather than human HLA), and the codon table is different, but the structure is identical. In 2025, Australian data analyst Paul Conyngham used this approach on his rescue dog Rosie, whose aggressive mast cell tumours had recurred after standard treatment. Her vaccine was synthesised at UNSW's RNA Institute and administered by a licensed veterinary oncologist, and her tumours shrank substantially in the months that followed.

Personalized mRNA cancer vaccines for dogs are an emerging modality, not a standard of care. They are not a replacement for surgery, radiation, or a vaccine like ONCEPT where those are indicated. Where they are most compelling today is as adjuvant therapy after the local tumour has been controlled. That is precisely the setting, and precisely the cancer, where the human melanoma data is most encouraging.

Questions to ask your veterinary oncologist

If your dog has been diagnosed with melanoma, these are good questions to bring to the appointment:

1. Where is the tumour, and what does that location mean for how it's likely to behave?
2. What did the biopsy show, and what is the mitotic index? Was immunohistochemistry needed to confirm it?
3. Did staging (lymph nodes, chest imaging) show any sign of spread?
4. What stage is it, and what's the realistic prognosis with versus without the treatment you're recommending?
5. Is wide surgical removal achievable here? If it means a mandibulectomy, maxillectomy, or toe amputation, what's recovery like?
6. Would radiation add meaningful local control in our case?
7. Is the ONCEPT vaccine appropriate for my dog, and how do you weigh its benefit given the mixed evidence?
8. Are there experimental options worth knowing about, such as clinical trials or personalized mRNA vaccines, and is our case a reasonable fit?
9. What does follow-up monitoring look like, and what are we watching for?

Where RosieVaccine fits in

RosieVaccine is a bioinformatics design service for veterinary oncologists. We take a tumour biopsy and a matched blood sample, identify the mutations that make your dog's specific cancer different from their healthy tissue, and design a codon-optimised mRNA vaccine targeting those mutations. The vaccine is manufactured by our CDMO partner and shipped back to your veterinary oncologist for administration.

We are in closed beta and accept a small number of pilot cases per quarter. Melanoma, with its strong human precedent for personalized vaccines and its real need for better control of distant spread, is one of our primary areas of interest. If you are a pet owner whose dog has been diagnosed with melanoma, the right way to learn whether a personalized mRNA vaccine could be part of their treatment is to discuss it with your veterinary oncologist, and have them request a pilot case through the form on our home page.