Mouth tumors in dogs (melanoma, epulis, carcinoma)
A mouth tumor is a growth that develops on the gums, palate, tongue, or inside of the cheek. There are several types. Melanoma is the most common malignant mouth tumor in dogs: it is often black, but can also be pink. Epulis, which grows on...
What is it?
A mouth tumor is a growth that develops on the gums, palate, tongue, or inside of the cheek.
There are several types. Melanoma is the most common malignant mouth tumor in dogs: it is often black, but can also be pink. Epulis, which grows on the gums, is often benign. Carcinoma and fibrosarcoma are other malignant tumors that can invade the jawbone.
Because a dog's mouth is rarely examined closely, these growths are often discovered late. Only a tissue sample from the growth, analyzed in a laboratory, can determine what type of tumor it is.
Commonly observed signs
These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.
Related signs — each one links to its page:
A visible growth in the mouth that is black, pink, or red, sometimes damaged on the surface, which may bleed.
Unusual bad breath.
Excessive drooling, sometimes tinged with blood.
Bleeding from the mouth: traces of blood on toys or in the food bowl.
Difficulty chewing: the dog drops food or chews on one side only.
Loose or missing teeth in one specific area.
Swelling of the face, jaw, or under the eye.
Pain: the dog resists touching around the mouth, eats less, and may lose weight.
Redness or bleeding limited to one area of the mouth should suggest a tumor rather than gum disease, which typically affects multiple teeth.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
The exact cause of these tumors is not known.
Certain breeds are affected more often by oral melanoma, suggesting a hereditary component.
Certain breeds appear to be at higher risk for oral melanoma, particularly Chow Chows, Cocker Spaniels, Dachshunds, Golden Retrievers, Gordon Setters, and Miniature Poodles.
These tumors mainly affect middle-aged and older dogs.
However, all dogs can be affected regardless of breed.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
The veterinarian examines the entire mouth, sometimes under sedation to see hidden areas clearly.
The lymph nodes under the jaw are felt to check whether the tumor has spread there.
A tissue sample from the lump is analyzed in a laboratory to determine whether the tumor is benign or malignant and which type it is.
X-rays or a head scan show whether the jawbone is affected.
Chest X-rays or a chest scan look for spread to the lungs.
This workup guides the choice of treatment.
Treatment
Surgery is the main treatment: it removes the lump with a margin of healthy tissue around it.
When the tumor involves the bone, the surgeon may need to remove part of the jawbone. While this may sound dramatic, dogs usually adapt well and resume eating afterward.
Depending on the tumor type and extent, radiotherapy, chemotherapy, or immunotherapy may be recommended, often at a specialized center.
Pain is managed by the veterinarian, and diet is adjusted to include soft food if the dog has difficulty chewing.
Never attempt to pull out, cut, or burn a lump in the mouth yourself.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
There is no known way to prevent these tumors.
Early detection is the best strategy: examine your dog's mouth regularly—the gums, palate, and underside of the tongue—such as when brushing teeth.
Have any lump checked, even if small and painless: the sooner it is removed, the simpler the surgery.
The annual veterinary visit includes an oral examination.
Possible complications
Spread to the lymph nodes and lungs, especially with melanoma.
Bone involvement of the jawbone, with tooth loss and pain.
Recurrent mouth bleeding.
Difficulty eating and weight loss.
Tumor recurrence at the surgical site if the tumor could not be fully removed.
When to see a veterinarian
Your dog's mouth is bleeding and the bleeding does not stop: seek care the same day.
It cannot eat or drink: seek care the same day.
You notice a lump on the gum, palate, tongue, or inside of the cheek, regardless of color.
One side of the face or jaw is swollen.
It has new bad breath, is drooling more than usual, or is dropping food.
A tooth is loose or has fallen out while the other teeth appear healthy.
Prognosis
The prognosis depends on the tumor type, size, location, and extent at the time of diagnosis.
A benign epulis completely removed generally has a good prognosis.
Malignant tumors, particularly melanoma, are more serious because they can spread; when discovered early, small, and completely removed, they offer the best outlook.
The veterinarian can provide a more precise estimate once the tumor type is identified.
Frequently asked questions
Lump in the Mouth or Gum Disease: How to Tell the Difference?
Gum disease generally affects several teeth, with tartar and red gums in various areas. A tumor, on the other hand, typically forms as an isolated lump in just one spot, which grows and may bleed or cause neighboring teeth to loosen. If in doubt, have your veterinarian examine the mouth.
A black spot on the gum, is it necessarily a melanoma?
No. Many dogs naturally have black, flat areas on their gums or palate. What should raise concern is a raised lump, or a patch that changes, grows, or bleeds.
Is a pink lump more reassuring?
Not necessarily. Melanoma is often black, but it can also be pink. Only analysis of a biopsy can determine the nature of a growth.
My dog has been drooling and rubbing his mouth since this morning: could it be a tumor?
Such a sudden onset suggests more of a foreign object stuck in place, like a stick or bone lodged across the palate. If you can do so safely, look inside its mouth and consult a veterinarian promptly. A tumor, by contrast, develops gradually over weeks.
References
Content reviewed by the TunisieVet editorial team · Updated 10 October 2026
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