Oral melanoma in dogs is an aggressive form of mouth cancer that, sadly, doesn’t typically carry a good long-term prognosis. To help dog parents process an oral melanoma diagnosis, integrative veterinarian Dr. Julie Buzby explains the symptoms, diagnosis, staging, treatment, and prognosis for oral melanoma in dogs.
Finding a mass in your dog’s mouth (or having your vet find one during an exam or dental procedure) can make your heart sink. It is easy to jump to the worst-case scenario…cancer.
Sometimes that isn’t the case because masses in the mouth can be benign. However, in other situations, you hear your vet say the dreaded words “oral melanoma,” and your fears are confirmed.
What is oral melanoma in dogs?
Oral melanoma is a tumor that develops in the mouth due to the abnormal replication of melanocytes (cells that produce the pigment melanin, which gives color to the skin, eyes, toenails, and fur). The majority of oral melanomas are malignant (cancerous) and highly aggressive. They often invade the jawbone and metastasize (spread) to lymph nodes and other organs. Unfortunately, melanomas are the most common oral tumor in dogs.
What causes oral melanoma in dogs?
Veterinary researchers have not identified a specific cause for oral melanoma in dogs. However, age and breed do play a role. While cancer can develop at any age, oral melanomas typically affect senior dogs who are at least 10 years old. There are also breeds that are more susceptible to developing oral malignant melanomas, such as:
- Boston Terriers
- Boxers
- Chow Chows
- Cocker Spaniels
- Dachshunds
- German Shepherds
- German Shorthaired Pointers
- Golden Retrievers
- Gordon Setters
- Labrador Retrievers
- Poodles (miniature)
- Scottish Terriers
Clinical studies indicate these breeds may be at a higher risk of oral melanoma because they normally have darker pigmentation of the oral cavity (gums, tongue, and hard palate).
What are the symptoms of oral melanoma in dogs?
Early on, growth of an oral melanoma may not initially cause any symptoms. Veterinarians often discover small masses incidentally during routine physical exams or dental cleanings. However, oral melanomas can cause significant pain as they grow larger, invading the soft tissues or moving into the jawbone. Then you might notice symptoms such as:
Black or pink mass in the mouth
Your dog may have visible abnormal tissue growth in the mouth. Melanomas on the gums, tongue, or inner cheek are usually raised and round. But on the hard palate, melanomas are more likely to be flat plaques. There also might be areas of ulcerated or necrotic tissue on or around the mass, and the mass tends to bleed easily.
Since melanocytes produce the dark brown to black pigment melanin, most malignant melanomas are dark or black in color. However, certain tumors, called amelanotic melanomas, arise from melanocytes but do not contain dark pigment granules. This results in a pink or white tumor.
Normal variations in a dog’s mucous membrane color, coupled with a poorly pigmented growth, can make a diagnosis of oral melanoma challenging.
Excessive or increased drooling
Dogs may drool if they are unable to close their mouths properly due to the tumor. Melanomas that grow on the gums or the inner cheek can interfere with normal tooth alignment and mouth closure.
Bad breath
Bad breath in dogs (halitosis) can occur secondary to infections or necrotic (dead) tissue associated with an oral tumor.
Bleeding from the mouth
The dog may be bleeding from the gums due to inflammation or infection below the gumline. Or the tumor itself may be bleeding. You might see bloody drool or blood on your dog’s toys, food, and water dishes.
Loose or missing teeth
Tumor invasion or gum disease can damage the tooth roots, leading to wiggly teeth and the dog losing teeth. The teeth may also be crooked or shifted from their normal location.
Difficulty eating and/or swallowing
Dogs may have trouble eating if their mouths hurt or the melanoma gets in the way of normal chewing. Also, tumors located toward the back of the mouth can make swallowing difficult.
Lack of appetite
Nausea, pain, and/or a tumor located somewhere that makes it difficult to chew and swallow may lead to a poor appetite or even complete refusal to eat. As a result, the dog may lose weight.
Coughing
If a malignant oral melanoma spreads to the lungs, the dog may start coughing. This is usually a late-stage symptom.
Swelling of the face, jaw, or neck
The dog might have a swollen face, jaw, or neck due to enlargement of the local lymph nodes or invasion of the jawbone by tumor cells.
If you see these symptoms, head to the vet
Various types of mouth cancer in dogs and non-cancerous growths, plus dental disease in dogs, dog tooth abscesses, and other dental problems, can cause many of the symptoms above. The best thing you can do in that situation is to promptly make an appointment with your vet.
How will the vet diagnose your dog with oral melanoma?
If you suspect that your dog has an abnormal growth in his or her mouth, scheduling a visit with your veterinarian is the first step in getting an accurate diagnosis. During the appointment, your vet will thoroughly examine your dog. Then he or she will give recommendations about which diagnostic tests will be most helpful in identifying the growth.
It’s important to note that oral melanomas are not the only type of tumor that can grow in a dog’s mouth. Other common oral tumors seen in dogs include squamous cell carcinomas (SCC) and fibrosarcomas. Additionally, dogs may develop benign growths such as gingival hyperplasia (an overgrowth of gum tissue) and epulis, also known as a peripheral odontogenic fibroma.
The vet will need to determine if your dog has an oral melanoma or one of these other mouth tumors. If your dog has a mass in his or her mouth, some of the most common tests to expect include:
Fine needle aspirate (FNA)
To perform a fine needle aspirate, the vet will use a small needle and syringe to try to pull cells directly from the mass. Unfortunately, FNAs are not always helpful because melanomas tend not to shed cells easily. This may make it difficult to collect enough cells to reach a diagnosis.
Sometimes the vet will also perform an FNA of lymph nodes in the area to look for tumor spread. This information helps the vet or veterinary pathologist determine the stage of melanoma the dog has.
Biopsy
Especially when it comes to oral melanomas, a biopsy is the diagnostic test of choice. In some cases, the vet may biopsy a portion of the mass first. This helps him or her know what kind of mass it is and the best way to approach it. For this type of biopsy, the vet will anesthetize your dog and collect a slice of the mass.
The other place a biopsy comes into play is after the surgeon has removed the mass completely. Typically, the vet will submit the whole mass and surrounding tissue to the diagnostic lab for microscopic analysis. This confirms the mass identity and determines if it was removed completely.
Recognizing a classic melanoma under the microscope is usually fairly straightforward due to the presence of melanin granules. However, sometimes the veterinary pathologist will need to use special stains (immunohistochemistry) to accurately identify amelanotic melanoma cells.
Imaging
The vet may also recommend imaging studies to look for evidence of tumor spread to the bone, local lymph nodes, or distant organs like the lungs. X-rays of the skull and chest are helpful for identifying bony involvement of the jaw and metastasis to the lungs. When looking for metastasis to the lymph nodes and internal organs, CT scans and abdominal ultrasound are usually the best options.
Bloodwork and urinalysis
Blood tests for dogs and a urinalysis can’t tell you if your dog has cancer. But they do give an overview of your dog’s general health. Since dogs often need sedation or anesthesia for diagnostic testing or treatment, having accurate information about organ function and blood cell numbers is essential.
What are the stages of oral melanoma in dogs?
Tumor staging has long been a crucial part of cancer treatment in humans, and now it is in dogs, too. The World Health Organization established tumor staging guidelines for oral melanoma in humans, which crossed over to veterinary medicine in 2016.
Based on your dog’s clinical history, diagnostic results, and biopsy findings, the veterinary pathologist will categorize your dog’s oral melanoma into one of four stages.
- Stage 1: Tumor size <2cm with no lymph node involvement and no metastasis
- Stage 2: Tumor size 2-4cm with no lymph node involvement and no metastasis
- Stage 3: Tumor size >4cm with or without lymph node involvement and no metastasis, OR any size tumor with lymph node metastasis
- Stage 4: Tumor of any size with evidence of lymph node involvement AND metastasis to other organs
What is the treatment for oral melanoma in dogs?
The veterinarian will use your dog’s tumor stage, location, and size to create a treatment plan. It may involve:
Surgical removal of the mass
Surgical removal of the mass with wide tissue margins is the preferred treatment of canine oral melanomas. The goal is to remove the visible tumor as well as enough tissue around it so that no cancer cells remain in the area. This is referred to as having “clean margins” and it may offer a better prognosis.
Sometimes your family veterinarian will perform the surgery. However, if the tumor is large or has significantly invaded the jawbone, the dog may need more radical surgical intervention. In this situation, your veterinarian will refer you to a veterinary specialist (surgeon, dentist, and/or oncologist) for evaluation and treatment.
Removal of part of the tongue or jawbone
In some cases, the specialist may end up removing part of the tongue or lower jaw (mandibulectomy) or upper jaw (maxillectomy). While it may seem extreme, this approach is sometimes necessary to relieve pain and give the best chance for complete excision of the tumor.
Dogs who lose part of the jaw or tongue have a slower recovery time because they often require a feeding tube until they re-learn how to pick up food, chew, and swallow again. Pain management and lots of TLC are key to keeping your dog as comfortable as possible during the recovery period.
Lymph node biopsies or removal
During surgery, your veterinarian may sometimes also need to biopsy and/or remove local lymph nodes. The submandibular (under the jaw), retropharyngeal (back of the throat), and prescapular lymph nodes (just above the shoulder joint) are typically the first sites for metastasis, as they are the closest sites to the primary tumor. Thus, they are the ones the surgeon most commonly ends up removing or biopsying.
Radiation therapy
Aggressive surgical resection is not always possible due to the size or location of the tumor. In these cases, radiation therapy is an option for tumors that are not amenable to surgery. It may also be helpful for shrinking larger tumors before surgery.
Oncept (melanoma vaccine)
An exciting immunotherapy option for dogs diagnosed with melanoma is the melanoma vaccine for dogs (Oncept® Canine Melanoma Vaccine). It is not a preventative vaccine, meaning it will not stop melanomas from developing.
Instead, it is a valuable tool for dogs who have already had a tumor surgically resected. The vaccine helps target microscopic disease that may still be present at the surgical site and reduces the risk of local recurrence. Additionally, some vets may use the melanoma vaccine in cases where the tumor cannot be removed surgically.
Dogs who are good candidates for the melanoma vaccine receive an initial series of four vaccines, given two weeks apart, with booster vaccinations at six months and one year.
Chemotherapy
Traditional chemotherapy is not an effective treatment for many cases of oral melanoma. And adding chemotherapy to surgical treatment or radiation therapy does not lead to a significant increase in survival time, regardless of the drug used. Veterinary oncologists have tried several chemotherapy agents like carboplatin, cisplatin, and piroxicam, with documented response rates only averaging between 18% and 30%.
Palliative care
Some dog parents may choose palliative care rather than pursuing surgery, the melanoma vaccine, or other treatments. And even for dogs who do undergo treatment initially, the focus may switch to palliative care near the end of their lives. There are veterinarians who specialize in hospice care for dogs. Your dog’s oncologist or family veterinarian can also walk you through the ways to help keep your dog comfortable.
You know your dog better than anyone, and it’s valid at any point to choose comfort-focused, palliative care if that feels like the kindest path for the time you have left together.
As the oral melanoma progresses, it will become more and more important to monitor your dog’s quality of life. Sometimes, using a quality of life scale for dogs on a weekly basis can be helpful. Other dog parents may choose to mark good days with green, okay days with yellow, and bad days with red on the calendar as a visual representation of their dog’s quality of life. The key is to find a method that works for you and your family.
What is the prognosis for dogs with oral melanoma?
The prognosis for oral melanoma depends on the size and location of the tumor, the stage, and the dog’s overall health at the time of diagnosis. As a general rule, tumors that are smaller and closer to the front of the mouth carry a better overall prognosis. Unfortunately, though, in many scenarios, survival times are less than 12 months.
Numbers in the veterinary literature vary significantly when it comes to survival times, so the goal here is to give you a general idea of what to expect.
A 2022 Veterinary Sciences article, Treatment of Canine Oral Melanomas: A Critical Review of the Literature, compiles the information from 81 studies on oral melanoma. However, if your dog has been diagnosed with oral melanoma, your best option is to talk with your veterinarian or the specialists you are working with. They can let you know how the specifics of your dog’s case may influence his or her predicted life expectancy.
Prognosis with surgery alone
Dogs that only undergo surgery reportedly have a median survival time (time after which half are still alive) between 5 and 18 months, with an average of approximately 12 months. The one-year survival rate for these dogs is 21-27%. Sadly, this means only about one-fourth of dogs whose tumors are removed surgically will still be alive one year after treatment.
When divided based on the stage, average survival times with surgery alone are:
- Dogs with stage 1: 12 to 17 months
- Dogs with stage 2: 6 to 12 months
- Dogs with stage 3: 3 to 12 months
- Dogs with stage 4: 1 month
Prognosis for radiation therapy
Dogs treated with radiation therapy have average survival times of 7 to 12 months. The overall response rate for radiation therapy is generally excellent, ranging from 83% to 100%. Studies have shown that the remission rate for dogs treated with radiation therapy is about 70%. However, in the event these dogs relapse, their survival time from that point is often only another 5 to 7 months.
Prognosis with Oncept melanoma vaccine
Interestingly, treatment with the Oncept vaccine alone has an average survival time of 7 to 13 months. However, when used in conjunction with surgery or radiation, clinicians have documented survival times of up to about 20 months.
Prognosis without treatment
Without any treatment, oral melanoma in dogs has a median survival time of about 65 days. This means that within two months of diagnosis, half of the dogs with oral melanoma will have succumbed to their disease if no treatment is pursued.
Comfort for the hard times ahead
Learning that your dog has oral melanoma can feel overwhelming. And it’s completely normal to have questions about what to expect. Your veterinary team can help you better understand the available treatment options and determine which ones will be most effective for your dog.
Ultimately, choosing whether to pursue treatment is a deeply personal decision. It’s okay to feel uncertain. If you’re having a hard time deciding, leaning on trusted family members, friends, clergy, or a counselor can help you sort through your thoughts and emotions.
They can also be a great source of comfort as you prepare for your dog’s euthanasia and grieve his or her loss. Know too that there are a variety of pet loss support resources (and ways to help a child through the loss of a pet). You don’t have to face this journey alone.
Did your dog have an oral melanoma?
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