What is Mouth Cancer in Dogs?

what is mouth cancer in dogs

A mouth cancer in dogs is a cancer that develops due to abnormal growth of the cells in the mouth. 

The dog’s mouth has different types of cells (skin, bone, fibrous) and tissues (hard and soft tissues) and they can all start proliferating without control, grow into cancer cells, and invade the surrounding tissue. 

Some types of cancer in the mouth (oral cancers) grow slowly and without spreading (benign tumors), while others have rapid growth and ability to spread to other parts of the body (malignant tumors).   

The most common types of oral cancer in dogs are oral melanoma, squamous cell carcinoma, ameloblastoma, and oral sarcoma. Out of these, the most common oral tumor in dogs is melanoma. 

Mouth cancer in dogs is relatively common type of cancer. According to MedVet, mouth tumors account for 6% of all canine cancer in dogs. 

What does Cancer Look Like in a Dog’s Mouth?

Mouth tumors in dogs look like large and often bleeding masses. They can grow at all areas of the mouth, but the most common site is the gingiva (gums). The mass or lump can be pigmented or non-pigmented and either smooth or with a cauliflower-like texture. 

Is Oral Cancer in Dogs Painful?

Yes, mouth cancer in dogs is painful. Dogs with oral tumors show obvious signs of oral pain – reluctance to eat, yelping when chewing, trouble swallowing, excess drooling. In general. dogs are good at hiding pain. However, the healthy appetite combined with inability to eat  is a telltale sign. 

How Fast Does Oral Cancer Spread in Dogs?

Oral cancer in dogs has the ability to spread really quickly, both within the pet’s mouth and to distant parts of the body (regional lymph nodes, lungs, abdominal organs). More often than not, a small lump can turn into a big mass within a matter of weeks. 

What Causes Mouth Cancer in Dogs?


The exact cause of mouth cancer in dogs is unknown. Usually the abnormal growth of cells in the pets’ mouths is a result of several carcinogenic factors working together. Here are the risk factors contributing to mouth cancer in dogs:

  • Environmental risk factors. Exposure to carcinogen chemicals (pesticides, asbestos, volatile organic compounds, tobacco smoke) increase the dog’s risk for developing oral cancer. 
  • Genetic risk factors. The incidence of mouth cancer in dogs is higher in breeds like Weimaraners, Chow Chows, German Shepherds, Boxers, Miniature poodles, and Cocker Spaniels. 
  • Individual risk factors. Oral tumors can occur in dogs of any age, but the most common age of affected dogs is 11 years. Also, male dogs have a higher risk of developing mouth cancer. 

What are the Symptoms of Mouth Cancer in Dogs?

From particularly bad breath to inability to eat kibble – many signs and symptoms indicate mouth cancer in dogs. Here are some clinical signs of oral cancer in dogs:

  • Bad breath (halitosis)
  • Excessive drooling
  • Bleeding gums
  • Difficult time chewing food
  • Trouble swallowing 
  • Reluctance to eat 
  • Signs of oral pain 
  • Growths in the upper or lower jaw 
  • Weakened teeth or teeth loss 
  • Lumps in the oral cavity 
  • Periodontal disease 
  • Facial swelling 
  • Weight loss  
  • Enlarged local lymph nodes.

These common signs of oral cancer may not be present simultaneously and sometimes depend on the exact location of the tumor. However, they will show up at some point. 

The signs of this disease are relatively easy to spot – as a dog owner, one becomes aware of the problem early on and does not have to wait for regular vet exams to find out something is wrong. 

Diagnosing Mouth Cancer in Dogs


To establish a mouth cancer in dogs diagnosis veterinarians perform a thorough physical examination and order certain diagnostic tests and procedures. Here is a short review of the diagnostic process for mouth cancer in dogs. 

Physical Examination. Your family veterinarian would usually examine the inside of your dogs’ mouth for any signs of swelling, visible mass, or any other abnormalities. Since most dogs would not allow their mouths to be probed like that, they are usually sedated for a thorough check. The aim here is to determine the size of the tumor. 

Lab Tests. A member of the veterinary team will take blood for blood work (complete blood count and biochemistry panels), and urine samples for urianlysis. The next step depends on the results from these analysis and it involves either additional scans or biopsy of the tumor. 

Different Scans. An X-ray for your dog’s chest is ordered to see if the tumor has spread to the lungs. Sometimes, a dental radiographs, an abdominal ultrasound, CT scan and an MRI scan are also recommended to see how invasive the cancer is and the available treatment options.

Biopsy. Once it is confirmed that your dog has oral cancer, a tissue biopsy (small piece of the tumor) is removed and examined under a microscope to determine the type of cancer. Alterantively, the vet may use fine needle aspiration (FNI) for the same purpose. Sadly, in most cases the FNI or biopsy of the tumor shows a malignant melanoma. 

After performing these tests, the primary care veterinarian may refer the dog to a veterinary oncologist for a definitive diagnosis or specialized treatment. 

How do You Treat Oral Cancer in Dogs?

The cancer in dogs treatment is complex and often includes using various approaches together. The best treatment depends on the type and location of your dog oral tumor, time of diagnosis,  and the dog’s age and overall health. Here are the available treatments for mouth cancer in dogs.  

Surgical Removal. Surgical excision is the most effective treatment. If affected, the vet will remove the regional lymph nodes in the and some of the pet’s teeth. In case, the tumor has spread to the bone, a portion of the upper jaw or lower jaw will also be removed. This is a more aggressive surgery. Before performing the surgical removal, the owner must be informed about the general anesthesia risk.  

Radiation Therapy. Radiation is often combined with surgery. The radiation treatment is particularly successful in dogs with ameloblastomas. However, the procedure works well for other types of mouth cancer in dogs too. 

Chemotherapy. Chemotherapy is rarely recommended for dogs with oral cancer. However, it can be considered an option in cases when the primary tumor has spread from the dog’s mouth and formed distant metastasis. It should be noted that dogs may experience certain side effects of chemotherapy. 

Oral Melanoma Vaccine. The oral melanoma vaccine is a novel form of immunotherapy recommended for dogs with stage II and stage III tumors. The vaccine is called ONCEPT and represents an innovative approach that supports other treatment options and prolongs the dog’s survival time. 

Cannabidiol (CBD) Products. CBD is not a cure for canine tumors of the mouth. However, as a safe and effective holistic remedy, CBD may help mitigate the cancer symptoms. We recommend the Honest Paws CBD Collection for dogs. The brand offers a variety of CBD products that are premium quality and easy to use. 

What can I do to Prevent Mouth Cancer in Dogs?


How to prevent cancer in dogs is a difficult question. The reason for this is that the root of mouth cancer development in dogs is unknown. 

The best chance of decreasing your dog’s risk of developing mouth cancer is ensuring good lifestyle (proper exercise and high-quality diet) and practice regular veterinary checkups. Early detection and early diagnosis improve the prognosis. 

Since oral cancer tumors are so uncertain, having pet insurance could help you financially and make sure you give the best possible care for your dog. We suggest the OneVet pet insurance offers to ensure your dog’s health and safety. 

How Long Can Dogs Live with Mouth Cancer?

Since there are different kinds of cancer of the mouth, the prognosis depends on the type and stage. Depending on the success of the surgical treatment, a dog diagnosed in the early stages can live a long and happy life. 

However, the prognosis is poor for dogs with malignant oral tumors. The average survival time for later stages of cancer is only 65 days. With management, these dogs have between 6 months and 1 year to live. 

How Long can a dog Live with Oral Melanoma?


On average, the median survival times for patients with oral melanoma is17 to 18 months for stage I, 5 to 6 months for stage II, and 3 months for the advanced stage III. These numbers are devastating considering that oral melanoma is the most common type of tumor in the dog’s mouth. 

If the canine oral melanoma tumor is unmanageable or in a too advanced stage, or for example, the dog’s quality of life is severely compromised, the medical advice for pet owners is euthanasia. Oral malignancies can be painful and proper pain management is not always possible.