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Informative Guide to Mouth Cancer in Dogs (2023)

Mouth cancer in dogs is a serious and complicated topic. If you believe there’s something going on in your dog’s mouth, it’s important to have it checked by a licensed veterinarian.

Unfortunately, oral growths in dogs may not be that obvious. And let’s face it; not every dog will eagerly let you poke around in his/her mouth.

You might not realize anything is wrong until you notice bloody drool, blood spots in their toys, pawing at the mouth, or you notice your dog is favoring one side of the mouth when trying to eat.

Of course, even if you see a lump, it’s impossible to tell whether it’s benign (non-cancerous) or malignant (cancerous). Only a trained veterinarian can make a definitive diagnosis.

This post will help you understand the most common types of oral cancer. Keep reading to learn more about dog mouth cancer, treatment options, and dog life expectancy.

Common Types of Mouth Cancer in Dogs

The three most common types of oral cancer in dogs are melanoma, squamous cell carcinoma, and fibrosarcoma. They all have very similar signs and it’s impossible to tell which type of cancer they represent without a veterinarian’s diagnosis.

Malignant Melanoma of the Oral Cavity in Dogs

Malignant melanoma is a common oral tumor. They can actually occur in different parts of the body including the skin, hair, and eyes. When they appear in the mouth, they tend to show up on the lips, gums, tongue, or hard palate on the roof of the mouth.

The veterinarian may refer to it as a “melanocyte tumor”.

These tumors consist of pigment-producing cells called melanocytes. Unfortunately, there’s no absolute explanation for why dogs develop these tumors. You might naturally think that it’s caused by too much sun, but that isn’t necessarily the case.

It’s thought that malignant melanoma in dogs could be brought on by a combination of genes and environmental factors.

Breeds more likely to develop oral melanoma include:

  • Cocker spaniels
  • Chow chows
  • Scottish terriers
  • Poodles
  • Golden retrievers
  • Dachshunds
  • Boston terrier
  • Springer spaniel
  • Doberman Pinscher

At the end of the day, any dog can develop malignant melanoma. Oral cancer is generally seen in older dogs. The average age of diagnosis is 11 years old. That said, it can occur in dogs of any age.

Not all oral tumors in dogs are cancerous

What Does Malignant Melanoma on a Dog Look Like?

Oral tumors of the mouth tend to be dark (brown or black). In some cases, they appear pink or tan. Oral cancer appears as swellings or lumps on the gums or on the roof of the mouth. They tend to break open and bleed, which can result in infection.

How Serious is Malignant Melanoma in Dogs?

Sadly, malignant melanoma can aggressively spread to the local lymph nodes and to other parts of your dog’s body. The life expectancy for a dog with this type of mouth cancer depends on three things:

1. How quickly the dog is diagnosed (the earlier the tumor is found, the better the outcome).

2. Whether the cancer has spread.

3. Types of treatment options chosen.

Unfortunately, the average survival time for dogs with malignant melanoma mouth tumors is

Clinical signs of oral cancer could include:

  • swelling under the jaw or around the neck
  • facial swelling
  • bad breath (halitosis)
  • bleeding from the mouth
  • trouble chewing
  • signs of oral pain
  • excessive salivation
  • loss of appetite
  • extreme fatigue

Diagnosing Malignant Melanoma in Dogs

A biopsy is typically required in order to obtain an accurate diagnosis.

This usually involves putting the dog under general anesthesia, taking a sample of the tissue and examining it under a microscope. If cancer is detected, the dog is further examined and the tumor is “staged”. 

A full physical exam, including blood work, is required to accurately stage malignant malignancy.

This typically includes a complete blood count, urinalysis, and x-rays of the chest to see if the cancer has spread. Ultrasound or radiography are also used to look for signs of disease in the abdomen.

The doctor may also want to check the lymph nodes to determine whether the cancer has spread.

Treating Malignant Melanoma in Dogs

Surgical excision is recommended for oral tumors. Unfortunately, malignant oral tumors tend to spread to the underlying jaw bone.

When that happens, the underlying bone and regional lymph nodes are removed. This allows them to be examined for signs of further spread within the body.

In some cases, especially when cancer is in advanced stages, surgery may not be recommended at all.


Radiation can be used to try and shrink tumors in preparation for surgery. Shrinking the tumor(s) may provide a better chance of completely removing them.

Radiation isn’t an effective treatment for oral cancer on its own. It involves putting the dog under general anesthesia and may require several rounds of treatment.

If radiation is chosen as a way to improve a dog’s comfort level (for example, pain control), it is given less frequently.

A licensed veterinarian will discuss the side-effects of radiation. It can cause irritation to the skin, nausea, vomiting, diarrhea, and loss of appetite.

Although there’s no current medical data to say that chemotherapy will improve a dog’s prognosis, it’s still recommended for nearly all cases of oral melanoma. 

Unfortunately, melanoma tends to be resistant to chemotherapy.

Canine Cancer Staging for Oral Malignant Melanoma

If the veterinarian suspects your dog has malignant cancer, he/she may refer you to a veterinary oncologist for staging. 

The oncologist will be well-versed in malignant tumors and will be able to give you an approximate life expectancy based on staging.

The following stages represent average survival times for dogs. Remember that these can vary depending on the dog.

If we assume that surgical removal of the tumor occurs (with no other treatment options), you might expect the following:


The approximate survival time is one year. At this stage, the tumor is less than 2 cm.


The approximate survival time is 6 months. At this point, the tumor is between 2 cm and 4 cm.


The approximate survival time is 3 months. Here, the tumor is larger than 4 cm and has spread to the lymph nodes.


The approximate survival time is 1 month. This means there is advanced cancer spread to other organs with a low survival rate.

Some studies suggest that remission rates with radiation alone could be as high as 70%. That said, there is always the possibility of recurrence or more distant spread within the body. 

Life Expectancy of a Dog with Malignant Melanoma

Every dog is unique, and it’s difficult to predict how each one will react to treatment. You may read specific time-frames for life expectancy, but even that is really just an educated guess.

The veterinarian may be able to make an educated guess on your dog’s life expectancy. However, it’s important to take that with a grain of salt and remain hopeful. Your dog may respond differently to treatment than other dogs, for example.

Things like your dog’s age, the involvement of underlying conditions, other medications, and the strength of your dog’s immune system are just a few things to take into consideration when estimating life expectancy.

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Dog Skin Cancer Facts

Oral Squamous Cell Carcinoma in Dogs

Squamous cell carcinoma in dogs is the second most common oral cancer in dogs and accounts for about 5% of all skin cancers.

Squamous cell carcinoma develops from the cells of the epidermis. The skin is made up of numerous layers of cells, with the squamous layer at the top.

This includes the nail bed, paw pads, abdomen, back, ears, or nose. 

malignant melanoma is a common oral tumor in older dogs

What Causes Squamous Cell Carcinoma in Dogs?

The cause of this type of skin cancer in dogs isn’t well understood. It’s thought there could be multiple reasons, including environmental, genetics, or a hereditary component.

Exposure to ultraviolet rays could explain SCC in some dogs.

It’s also thought that exposure to papilloma-like viruses (benign tumors of the mouth) appears to contribute to multicentric SCC in the mouth.

This type of cancer is more common in cats than in dogs. Dogs are usually 10 years of age or older at the time of diagnosis. It can, however, sometimes occur in younger dogs.

These tumors typically appear under the tongue or on the gums.

Unlike other types of tumors, squamous cell carcinoma doesn’t usually spread to other organs. They can, however, invade the jaw bone and surrounding tissue. Unfortunately, they grow very quickly. 

Signs of Oral Squamous Cell Carcinomas in Dogs

Clinical signs of squamous cell carcinoma in dogs include:

  • Lesions are usually found in light-skinned areas.
  • Variable appearance. May look like small area of irritated, red, or ulcerated skin.
  • There may be plaques or crusts that develop on the area.

Oral cancer of any kind can cause the following common symptoms:

  • bad breath (halitosis) 
  • excessive drooling in a dog that doesn’t normally drool
  • blood-tinged drool
  • swelling of the face
  • difficulty eating
  • growths in the mouth (including on the gums)
  • Dropping food
  • poor appetite
  • weight loss 
  • vomiting
  • swollen lymph nose.

As always, early detection is crucial. If you notice any unusual lumps or bumps on your dog, be sure to have a veterinarian assess what is going on. 

The signs noted above do not necessarily mean your dog has mouth cancer. Periodontal disease can cause some of the symptoms listed above.

Life Expectancy of a Dog with Oral Squamous Cell Carcinoma

Oral cancer is one of a variety of cancers that dogs can get. Melanoma is the most common form of oral cancer, but it’s not the only one. In addition to melanomas, there are also:

  • Sarcomas
  • Squamous Cell Carcinomas
  • Ameloblastomas

The prognosis given to your dog will depend on a few factors. These include how quickly the diagnosis is made, treatment options available, and how advanced the cancer is. 

Generally speaking, dogs without treatment for oral cancer can expect to live approximately 2 to 3 months. That can sometimes be extended to 6-12 months given adequate treatment. 

It’s nearly impossible to get an exact life expectancy from a blog post. There are many factors that contribute to life expectancy, which makes it important to have a heart-to-heart with the veterinarian. 

Early diagnosis is crucial to a positive outcome.

When to Euthanize a Dog with Oral Cancer

This is a decision that no dog parent wants to have to make. Through discussions with the veterinarian or oncologist, you should be able to make an education assessment of when to let go. 

Assessing your dog’s quality of life is a useful tool to help you in this difficult time. We don’t want to see our dogs suffer, so if your dog is showing dramatic signs of decline, it may be time. 

If your dog is listless, not enjoying life, is in chronic pain, and cannot eat anymore, it may be time to consider the difficult decision of euthanasia.

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Works Cited

NC State Veterinary Medicine., Accessed 1 June 2022.

Vca., Accessed 1 June 2022.

CriticalCareDVM. CriticalCareDVM., 27 Mar. 2017,

Pet Health., 1 Feb. 2017,

Jennifer72. Dog Discoveries., 13 June 2017,

DVM, Demian Dressler. Dog Cancer Blog., 20 Nov. 2008,

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