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Everything you need to know about dog's mouth cancer

Dog mouth open
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Mouth cancers make up 6% of all dog tumours. Learn about the causes, symptoms and treatments of dog mouth cancer. 

By Nick Whittle

Updated on the 08/02/2021, 13:44

They are the fourth most common cancer of male dogs in particular. Dogs are three times more likely to develop mouth cancer than cats. But not all mouth cancers come with a serious risk to a dog’s life. Of oral tumours especially there are both good and bad (benign and malignant), and depending on when they are discovered the prognosis can be promising.

Two types of mouth cancer

The first kind of oral tumour we will look at is the benign kind. These are tumours that are localised and usually with well-defined edges. They do not contain the sort of cell that spreads around the body. Because they are reasonably well-marked benign cancers are relatively easy to remove and, once removed, pose no further threat to the animal. The following is known to be a benign tumour:


of this type of cancer a tumour forms usually on the dog’s gum. They tend not to spread very quickly but they grow bigger, which can eventually make her eating and breathing difficult. Most instances of epulides are seen in Boxers and squashed-nose breeds.

A malignant cancer on the other hand is the kind that spreads. It also tends to be rooted deeply at its site, making removal complicated and dangerous. Malignant cancers require expert intervention since it is likely by the point of diagnosis that the cancer has already spread. The following are the most common kinds of malignancy of a dog’s mouth:

Squamous cell carcinoma

This is a slow growing cancer but is nevertheless aggressive. It is not known to spread as much as other cancers but it is difficult to eradicate completely. More dogs aged between 6 and 10 seem to suffer with this cancer, and the following breeds are more prone:


Again a slow-growing tumour, a fibrosarcoma is not known to spread to other parts of the body. It is known however to be deeply embedded at site which gives surgeons cause of concern when removing it from the skull. The usual age of canine patients seen with the disease is similar to the age of those with squamous cell carcinoma. Golden Retrievers seem particularly prone to fibrosarcomas.

Oral melanoma

This is a fast-growing and exceptionally aggressive form of cancer that spreads quickly throughout the body. A dog that is confirmed to have this kind of cancer has a life expectancy of between just five and eight months. Breeds that show a high instance of melanoma include:

Oral osteosarcoma

This kind of cancer is thought to not metastasize (spread to other parts of the body) but its removal is complex. Pre-operative tumours in the bones of the skull cause extreme pain and can lead to neurological damage. Their excision is often only be possible by removal of the entire upper or lower jaw, or both, and there may be lasting damage to facial nerves. Breeds that seem more prone to this cancer include:

Causes of mouth cancer in dogs

There is no census on the cause of mouth cancer in dogs, although some vets speculate that exposure to sunlight may in the case of squamous cell carcinoma be a contributory factor to its growth. Dogs exposed to the same environmental contaminants as their owners are also likely to contract cancer (from such things as tobacco smoke and asbestos).

Symptoms of mouth cancer in dogs

Mouth cancers can be mistaken for more innocuous diseases and conditions such as an inflammation or an ulcer due to plaque or bacteria. However, regular checks of your dog’s mouth prove valuable for the detection of new growths and swellings, both of which are symptoms of cancer. The following other symptoms may be observed in the mouth of a dog with oral cancer:

  • Growths and lumps in the mouth
  • Swollen gums
  • Bleeding from any part of the mouth
  • Visible lesions (often white)
  • Breaths smell worse than usual

Of behaviour an owner may observe:

  • Difficulty chewing
  • Loss of appetite
  • Excessive salivation
  • Weight loss

Most oral canine cancer is detected by accident by owners who have watched their dog lie on her back with her mouth open or while they are brushing her teeth.

Treating a dog's mouth cancer

Oral tumours are most often removed if it is deemed prudent. A good proportion of the tissue surrounding an aggressively metastatic cancer is removed too. Sometimes a tumour may be so deeply embedded in the dog’s skull that its removal would not be compatible with the animal's survival.

Most oral cancers are detected by chance. © Pixabay

The likelihood of the dog’s recovery from mouth cancer depends on where in the mouth the cancer is sited, how advanced the tumour is (what metastases have been discovered) and what size the tumour is. The life expectancy of a dog with an aggressive metastatic cancer is in most instances less than six months following surgery. Although there is no definitive cause of oral cancer regular checks of your dog’s mouth lead to early identification of a problem.

A swift diagnosis and the timely removal of the tumour is a dog’s best chance of survival. In the case of mouth cancer: time is of the essence. Aftercare is of the utmost importance following surgery, and although recovery from a malignancy is limited your dog’s quality of life can be improved by sympathetic care and attention.

Your vet will advise you on how best to manage your dog’s recovery and may also recommend foods specifically designed for dogs recovering from cancer.