Causes of lumps or bumps in the mouth in dogs

Whenever we find a lump on a much-loved pet, it is not uncommon for our minds to leap straight to the worst-case scenario. While there are cancers that can produce malignant tumours in the mouth area, there are also non-cancerous causes. Your vet can test the lump if needed by taking a biopsy, which is another reason to make that vet visit promptly.

Benign lumps

Epulis, also known as gum boils, are the most common benign lump found in the mouth. The same colour as the gum and smooth in appearance, they are typically found between the canine or incisor teeth. They can be either low and rounded or at the end of a stalk, standing up from the lower jaw or hanging from the upper jaw. Older dogs are more likely to have epulis, over the age of six years, and they are common in flat-faced, brachycephalic breeds such as boxers, bulldogs and pugs. Although benign, as these boils grow in size they can begin to cause problems with eating, drooling, bad breath and making the teeth crooked by pushing them out of place. The vet can confirm that the lump is a boil and remove if it has become a problem.

Viral papillomas. While boils appear in older dogs, oral papillomatosis, caused by the canine papillomavirus, usually occurs in dogs under two years old. Their immune systems remain not fully developed enough at this age to be able to fight off viral conditions. These lumps are contagious between dogs and spread through direct contact between dogs. They appear as typically small cauliflower-shaped growths with a jagged surface, usually on the lips and muzzle. Most cases resolve naturally, disappearing on their own within a period of five to six months. Although rare, some papilloma growths can become malignant and so, on the discovery of the lumps, your vet should check them out.

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Mouth injuries. An injury that has gone unseen, like a foreign object such as a stick poking into the gum and leaving splinters when the dog was out of sight, a cracked tooth or undiagnosed and untreated tooth problems can result in infections in the mouth. If these occur within the gums, they could form an abscess, resulting in painful red swelling, with possible pus leakage and bad breath.

Malignant mouth tumours

A number of cancerous tumours can be found in the mouth of dogs, although three, in particular, are the most common.

Malignant melanomas are the most common form of mouth cancer in dogs. The melanoma forms due to an abnormality in the way that the cells that produce pigment in the body grow and divide. Malignant melanomas usually appear on the lips, gums and soft palate although can grow on the tongue. Dogs with pigmented mouths like the Chow Chow seem to be particularly prone. Other predisposed breeds include poodles, dachshunds and golden retrievers. Dogs with this type of tumour are usually older, having reached maturity. These tumours grow quickly and aggressively, causing facial swelling in the area of the growth, difficulty eating, bad breath and bleeding from the tumour itself, and can spread to other areas of the body such as the lungs and lymph nodes.

Squamous cell carcinoma more commonly associated with cats; this growth can also occur in dogs. The typical place to see this type of lump is the gingiva, the gum surrounding the teeth, causing bad breath, drooling and difficulty eating. This cancer is very aggressive and can, later in the disease’s development, spread through other parts of the body. If discovered near the front of the mouth, it may be possible to remove the mass surgically, and recovery is often good if this is the case.

Fibrosarcoma, aggressive and invasive within localised areas, this type of growth can also invade other areas in the body as the disease advances. Typically, they present as a red boil or ulcer on the mouth’s fibrous tissues and have a tendency to ulcerate and bleed. This kind does not tend to grow as fast as other types of oral tumour and may be able to be treated.

Other less common malignant tumours can occur in a dog’s mouth, and it is very important that a vet examines and diagnoses the cause of the lump as soon as possible, so appropriate treatment can begin.