Dog Mouth Cancer: Types, Symptoms, and Prognosis

There are a variety of different kinds of dog mouth cancer, as well as some masses or swellings in the mouth that are, thankfully, not cancerous. Integrative veterinarian Dr. Julie Buzby provides information about the most common types of masses in a dog’s mouth and discusses the symptoms, diagnosis, treatment, and prognosis for dog mouth cancer.

When you think about the various types of tumors that dogs can get, skin masses or splenic masses may come to mind first. But did you know that tumors in a dog’s mouth are the fourth most common tumor type in dogs and account for 6-7% of all dog tumors?

As such, it is important that dog parents are well informed about oral masses, including dog mouth cancer.

What is mouth cancer in dogs?

In dogs, mouth cancer occurs when there is uncontrolled growth of abnormal cells in the oral cavity (i.e. mouth). The end result is formation of a mass, which can damage the tissue in the area or spread to other places in the body.

Usually, oral cancer originates from gingival tissue (i.e. gums) and other structures in the mouth (e.g. palate, cheeks, lips, or tongue). However, the exact cause isn’t well understood. Some research suggests there may be environmental and genetic factors that come into play. For example, certain dog breeds may be at higher risk for developing oral cancers.

At-risk dog breeds include:

• Akitas
• Boxers
• German Shepherds
• Golden Retrievers
• Cocker Spaniels
• Collies
• Miniature Poodles
• Weimaraners
• Scottish Terriers

Generally, mouth cancer is most likely to occur in middle-aged to older dogs. But it is possible for younger dogs to develop oral cancer too.

What are the symptoms of dog mouth cancer?

The potentially good thing about mouth cancer is that you can see most of your dog’s mouth. This means that if you routinely examine your dog’s mouth as part of a weekly five-minute dog wellness scan, you may be able to catch a mass while it is small, and before it starts to cause any clinical signs.

Alternatively, the first thing you may notice is some of the symptoms of dog mouth cancer.

Growth in the mouth

In the early stages of dog mouth cancer, you may just see a small bump on the gums, palate, cheeks, lips, or tongue, or an area of red gums in dogs. But as the tumor continues to grow, it will usually become easier and easier to notice. Depending on the tumor type (which we will get to soon), the tumor may be smooth or bumpy, ulcerated or intact, and black or pink to red. And it might be almost anywhere in the dog’s mouth.

Excessive drooling

Especially when eating, your dog may drool excessively. This is the case because the mass can interfere with eating, swallowing, and other normal mouth movements.

Bloody saliva or bleeding from the mouth

If the mass is ulcerated, breaks open, or the dog accidentally bites the mass when chewing, it may begin to bleed. This may cause your dog to drip blood from his or her mouth or have blood-tinged drool.

Dropping food or chewing abnormally

Eventually, the tumor may make it hard for your dog to pick up or chew his or her food. As a result, you may notice your dog dropping food or moving his or her head around abnormally when chewing.

Difficulty swallowing

Especially if the tumor involves the back of the throat or is large, you may notice your dog coughing and gagging when attempting to swallow. Or the dog may make gulping sounds or toss his or her head around when swallowing.

Facial swelling or deformity

Depending on the type of tumor, you may also notice that one area of your dog’s face or jaw looks swollen or misshapen. This may be due to the effects of the mass on the bone and soft tissue in the region. Some types of cancer can be quite destructive and invasive.

Bad breath

Bad breath in dogs can also occur due to the effects of the tumor.

Loose teeth

Mouth cancer can destroy the tooth roots, as well as displacing the teeth. This means that the dog’s teeth may be crooked and/or loose around the mass. As a result, you might notice the dog losing teeth.

Swollen lymph nodes

Sometimes the dog’s lymph nodes (especially the submandibular lymph nodes under the chin) may become enlarged. This can happen if the mouth cancer spreads to the lymph nodes. But swollen lymph nodes can also simply be a reaction to the inflammation in the mouth due to the tumor.

Weight loss

If it goes on long enough, oral cancer in dogs can cause the dog to lose weight from an inability to eat and the toll that cancer takes on the body.

Pawing at the face

Due to pain, inflammation, or abnormal sensations, dogs with mouth cancer may paw at their mouth or rub their face against the ground.

What are the symptoms of oral masses that are not cancerous?

While we are mostly discussing cancer, it is important to know that there is some overlap between the symptoms of cancerous and non-cancerous masses, and some areas where they differ.

Dogs with benign masses will still have an obvious mass, and it may displace the teeth. But the teeth are usually firmly rooted, not loose like with cancerous masses. And unless the mass gets big enough that the dog is biting it, most dogs with benign masses don’t have oral bleeding or bloody saliva. They are also less likely to have bad breath, difficulty chewing or swallowing, weight loss, or some of the other more severe symptoms that accompany mouth cancer (but those symptoms can eventually occur if the mass gets big enough).

Now that you have an idea of what symptoms to watch for, let’s take a closer look at the types of oral masses, starting with the various mouth cancers.

What are the different types of oral cancer in dogs?

There are a number of different cells and tissues in a dog’s mouth the tumor can originate from, so there are several different types of mouth cancer in dogs. The three most common types of oral cancer in dogs are melanoma, squamous cell carcinoma, and fibrosarcoma.

Oral melanoma in dogs

The most common type of dog mouth cancer is oral melanoma, which almost always behaves malignantly (in other locations, melanoma sometimes has benign behavior). Also known as melanosarcoma, oral melanoma originates from pigment cells (melanocytes). Unfortunately, oral melanoma is the type of mouth cancer with the highest potential to spread to other areas, typically the lungs and lymph nodes.

Oral melanomas may look like round raised nodules with black pigment, but the amelanotic type can occur without pigment. Often the surface of the mass is ulcerated, and the tumor itself is friable (i.e. easily tears or starts bleeding). The mass may be on the dog’s gums, inner lips or cheeks, tongue, or palate.

Usually, oral melanoma occurs in dogs who are 10 years of age or older, but younger dogs can also be affected. And it tends to be more common in dogs with increased oral pigmentation.

Squamous cell carcinoma

The second most common type of oral cancer in dogs is squamous cell carcinoma (SCC). Most commonly, the tumor is found on the gingival tissue. However, it can occur on the tonsils or the tongue.

The tumor appearance can be variable. Some SCCs have lots of little bumps that look like cauliflower. But others may be an ulcerated mass or look like a non-healing ulcer within the mouth. Squamous cell carcinomas are commonly quite locally invasive. Tonsillar SCCs are much more likely to metastasize than SCCs on the gums, but all types have the potential to spread to the lungs or lymph nodes in the area.

SCC of the gingival is more common in middle aged dogs (7-9 years old). But tonsillar SCC occurs most frequently in older (10-12 year old) male dogs.

Fibrosarcoma

The third most common type of oral cancer in dogs is fibrosarcoma. These tumors come from the fibrous tissue in the gums, palate, inner cheek or lip, or bone around the teeth. Generally, fibrosarcomas are smooth, pinkish red oral masses. While they are locally aggressive, they can also spread to the lungs or lymph nodes.

Typically, fibrosarcomas tend to occur in middle-aged medium-to-large breed male dogs. However, they can occur in younger dogs, and tend to be more aggressive in that population.

Other cancers in a dog’s mouth

Additionally, dogs can develop the following types of malignant oral cancer:

• Osteosarcoma in dogs—Bone cancer in the mouth, which may cause a hard swelling of the upper or lower jaw plus a mass within the mouth
• Osteochondrosarcoma—Cancer that originates from cartilaginous structures and mostly affect large breeds
• Mast cell tumor in dogs—Usually originates from the skin but can sometimes occur in the mouth
• Hemangiosarcoma—Blood vessel cancer that many occur in or below the tongue

What are some non-cancerous masses in a dog’s mouth?

Up to this point, we have been talking about cancer. But thankfully, not all oral growths and swellings are malignant. There are also a variety of benign tumors, swellings, or cystic lesions that can occur in a dog’s mouth.

Some of the more common benign oral swellings or masses include:

Epulides (i.e. benign tumors from the periodontal ligament)

The term “epulis” (plural: epulides) has historically been used to refer to various benign tumors that come from the periodontal ligament (i.e. the ligament that anchors the teeth in place). However, these tumors may go by a variety of other names as well. The main types of epulides are:

• Peripheral odontogenic fibroma (fibromatous or ossifying epulides)—Pink, smooth non-ulcerated masses that appear on the gums. Dogs may have a single mass or multiple masses.
• Acanthomatous ameloblastoma (acanthomatous epulis)—Ulcerated mass with a rough surface that often occurs near the incisors or canines and can be confused with a squamous cell carcinoma.

Overall, epulides seem to be more common in brachycephalic dogs (e.g. Boxers or Bulldogs), Golden Retrievers, and Shetland Sheepdogs. Most affected dogs are middle-aged or older.

Other benign tumors

While less common than epulides, dogs can also develop the following benign oral tumors:

• Papilloma—Wart-like growths caused by a virus that typically affect dogs less than 2 years of age
• Osteoma—Slow-growing, bony oral masses that originate from the hard palate
• Plasmacytoma—Usually a gingival mass that looks like an epulis
• Hemangioma—Rare blood vessel tumor that can originate from any oral soft tissue structure (e.g., tongue, gums)

Gingival hyperplasia

Some dogs, especially Boxers and Bulldogs, can also develop an overgrowth of normal gum tissue around the teeth. This is known as gingival hyperplasia. While it isn’t a true tumor, the excessive amounts of gum tissue can still cause issues by trapping bacteria and debris. This predisposes the dog to dental disease in dogs.

Dentigerous cyst

Unerupted or impacted teeth have the potential to form a swelling known as a dentigerous cyst. These are fluid-filled cavities that develop around the tooth. Dentigerous cysts can expand, putting pressure on sensitive tissues and pushing neighboring teeth away from their normal location. Most dentigerous cysts occur in the jaw and, if left untreated, can cause jaw bones to fracture.

Oral abscess

Abscesses are cyst-like pockets of pus and fluid that develop as a result of trapped infection. When in a dog’s skin, these can stretch and become large swellings. But there isn’t a lot of stretchy tissue in a dog’s mouth. So in the case of a dog tooth root abscess, the swelling tends to move up and out toward facial skin. Many tooth root abscesses affect teeth in the upper part of the mouth, causing noticeable swelling beneath the eye. These abscesses can sometimes break open and bleed.

How is mouth cancer diagnosed in dogs?

Should you notice anything abnormal about your dog’s mouth or any potential symptoms of an oral tumor, the best thing you can do is schedule an appointment with your veterinarian.

Please do not assume that a lump in your dog’s mouth is no big deal just because it doesn’t quite match the description of the common types of cancer or your dog doesn’t seem bothered by it. And likewise, it is important to take any symptoms seriously. Mouth cancer, dental disease, and other dental conditions can be painful and require veterinary attention.

Physical exam and oral exam

During the examination, the veterinarian will look your dog over from head to tail, paying special attention to your dog’s lips, cheeks, tongue, gums, teeth, and palate. Additionally, he or she may recommend an oral exam under anesthesia. This allows the vet to get a better look at the structures in the mouth, including some that are harder to assess in an awake dog such as the underside of the tongue or the tonsils.

Fine needle aspiration (FNA)

While your dog is anesthetized, the veterinarian can also perform a fine needle aspiration (FNA) of the mass. As the name indicates, an FNA involves using a small needle to obtain cells from the mass and then examining them under the microscope. Sometimes this can provide a diagnosis. But in other cases, the mass may be too firm or the cells may not come out of the mass and into the needle very easily, making the FNA non-diagnostic.

Biopsy

Alternatively, the vet may decide to do an incisional biopsy of the mass. This involves taking a small section of tissue from the tumor and submitting it to a veterinary pathologist. Additionally, the vet may submit the entire mass to the pathologist after removing it. Biopsy (i.e. histopathology) is the gold standard diagnostic for mouth cancer since it provides the most definitive answers as to the tumor type.

X-rays

Finally, the veterinarian may also obtain X-rays of the teeth and jaw while the dog is under anesthesia. This allows him or her to assess how the tumor is affecting the bone and teeth in the region.

Additionally, if the vet suspects the mass is cancerous, he or she may take X-rays of the dog’s chest to look for metastasis to the lungs.

Advanced imaging

In some situations, the vet may also refer your dog for a CT scan. This can be a good way to further evaluate the tumor and look for evidence of spread to other locations.

Lymph node aspirates

Since mouth cancer sometimes spreads to the lymph nodes, the vet may recommend performing an FNA of the lymph nodes around the head and neck. This can provide valuable information for staging mouth cancer.

How is mouth cancer staged?

Based on the results of the diagnostics, the veterinarian can classify the dog’s mouth cancer into one of four stages:

• Stage I: Mass is less than 20 mm and does not involve the bone
• Stage II: Mass is 20-40 mm and does not involve the bone
• Stage III: Mass is over 40 mm, does not involve the bone, and has not metastasized OR a mass of any size that does involve the bone or has spread to the lymph node(s) on the side of the tumor
• Stage IV: Mass of any size that has spread to the lungs (or other distant sites) or has spread to lymph node(s) on both side of the body

The stage of mouth cancer will help guide the treatment, as well as influence the prognosis.

What is the treatment for dog mouth cancer?

Treatment will depend on the type of mass or swelling present. For non-cancerous swellings like dentigerous cysts, the entire affected tooth must be extracted, and then the lining of the cyst must be removed. This type of surgery is curative, and no further action is required other than to follow up with dental X-rays in about six months. And similarly, extracting the offending tooth will resolve a dog tooth root abscess.

Surgery

However, true oral masses may require surgical excision, even if they are benign. Sometimes the veterinarian, veterinary dentist, or veterinary surgeon can simply remove the mass. But in other situations, especially with aggressive oral cancer, the surgeon may need to remove a portion of the upper or lower jaw or tongue in order have the best chances of getting all of the cancer cells. While your vet may be comfortable with a simple benign oral mass removal, more complicated procedures often involve finding a veterinary specialist near you, usually a dentist or surgeon.

Radiation therapy

If it isn’t possible to remove the whole tumor, the vet or veterinary oncologist may recommend radiation therapy to kill the remaining cancer cells. Or in some cases, the oncologist may use radiation to shrink the tumor prior to surgery. Additionally, radiation is an option for some types of tumors that are unresectable (i.e. cannot be surgically removed). Some tumors are more responsive to radiation than others, so your veterinary oncologist will let you know what is right for your dog.

Chemotherapy

Most of the time, oral tumors in dogs don’t respond well to chemotherapy, so it isn’t a first choice for treatment. However, there may occasionally be situations where the veterinary oncologist recommends it as an adjunctive therapy.

Immunotherapy for oral melanoma

If your dog has oral melanoma, another potential treatment option is the oral melanoma vaccine for dogs (ONCEPT®). The vaccination causes the immune system to target and kill the cancerous melanoma cells. Typically, vets use the melanoma vaccine to address any remaining melanoma cells after surgically removing the visible tumor.

Natural treatments

While there are no natural treatments for oral cancer in dogs, natural anti-inflammatories and antioxidants like omega-3 fatty acids for dogs and vitamin A can provide some health benefits to cancer patients. Another supplement, turmeric, has been shown to have anti-cancer properties in lab settings, and it can reduce inflammation in dogs.

Supportive care

Dogs with mouth cancer may have trouble eating, so some may require a feeding tube for nutrition. Additionally, since oral tumors can be very painful, it is important to provide good pain control in the form of pain medication and alternative therapies such as acupuncture for dogs.

If you feel like your dog is painful or isn’t eating enough, please don’t hesitate to reach out to your vet. While comfort measures don’t treat the cancer itself, they are essential for maintaining your dog’s quality of life.

What is the prognosis for dogs with mouth tumors?

As you can imagine, the outlook varies significantly depending on what type of oral mass the dog has, the size and location of the mass, the stage of the cancer (if it is cancer), and the treatment plan.

Dogs with dentigerous cysts or abscesses tend to have a great prognosis with treatment. And dogs with benign growths also have good surgical prognoses. However, without surgery, they may only live for a few years before the cancer makes eating impossible.

On the other hand, oral cancer tends to carry a poorer prognosis. Since melanoma, squamous cell carcinoma, and fibrosarcoma are the most common types of mouth cancer, we will take a look at those.

Life expectancy for oral melanoma

Overall the prognosis for dogs with melanoma is poor, but the published survival times can vary significantly. One study reported that without treatment, dogs with oral melanoma only survive for an average of 65 days.

However, with aggressive surgical removal and sometimes adjunctive therapy, a Journal of the American Veterinary Medical Association article reported an average progression-free interval of 508 days and an average survival time of 723 days for dogs with oral melanoma. Yet a different study reported a median survival time of 206 days with surgery.

Life expectancy for oral squamous cell carcinoma in dogs

For SCC, the survival times and prognosis for dogs vary based on the location.

• Mandibular (lower jaw) SCC—Average survival time of 19-43 months with 1-year survival rate of 88-100%, 2-year survival rate of 79%, and 3-year survival rate of 58% with surgery alone.
• Maxillary (upper jaw) SCC—Average of 10-39 months survival time with maxillectomy (i.e. removal of a portion of the upper jaw).
• Tonsillar SCC—Average survival time of 243 days with 1-year survival rate of 40% and 2-year survival rate of 20%.

Life expectancy for oral fibrosarcoma in dogs

According to one study, when treated with surgery, the average survival time for dogs with fibrosarcoma was 743 days. Depending on the study, the chances of the tumor recurring varied between 24.1% and 54.2%.

Ask your vet what to expect for your dog

While it is possible to look at the survival times and recurrence rates in studies, each dog’s situation is unique. So the best way to get an idea of what to expect for your dog is to consult with your vet, veterinary dentist, or veterinary oncologist. Since they are familiar with your dog’s case and treatment plan, they are the best people to help you understand the outlook for your dog’s situation.

Additionally, as your dog enters the final stages of mouth cancer, your vet can help walk you through how best to keep your dog comfortable and give you advice about when to put down a dog with mouth cancer. Often the primary tumor, rather than metastasis tends to be what ultimately kills dogs with oral cancer. They will get to the point where they can’t eat, the tumor is bleeding frequently, or they are in significant pain and their quality of life is low. That’s when the kindest thing may be to set them free.

Partner with your vet and advocate for your dog

Facing a diagnosis of mouth cancer (or a mouth tumor in general) can be scary and overwhelming. Please remember to take it one day at a time and to work closely with your vet. He or she (as well as any specialists your vet may refer your dog to) are a wealth of information. They can help guide you through the diagnostic and treatment process and address any issues or questions that arise along the way.

Keep in mind too that you know your dog well, and you are his or her advocate. So if you feel like your dog is painful or isn’t doing well, please speak up. There may be things that the vet can do to help improve your dog’s quality of life. By sharing what you are seeing at home and any concerns you have, your vet can best help you and your dog.

Has your dog been diagnosed with mouth cancer?

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