Mast cell tumors (MCTs) are the most common malignant skin tumor in dogs — and one of the most treatable when caught early. Knowing what to look for and understanding your dog’s risk can make a real difference in outcomes.
At Embark, we now offer a genetic risk estimate that identifies your dog’s risk for developing MCTs. It’s based on your dog’s genetic ancestry and markers associated with the condition, and it comes with expert advice on how to use that information proactively. Here’s what you should know.
What are mast cell tumors in dogs?
Mast cells are a type of white blood cell that plays a normal role in your dog’s immune response — they’re part of the body’s defense against infection. Sometimes, though, these cells cluster together and form masses in or under the skin. These tumors account for roughly 11–21% of all skin tumors diagnosed in dogs.
MCTs are typically palpable, meaning you can feel them with your hand. They’re most commonly found on the head, neck, limbs, or trunk, though they can occasionally affect internal organs — in which case they typically can’t be felt from the outside.
The encouraging news: if caught early, mast cell tumors are treatable. More than 80% of mast cell tumors are curable by surgery alone.
What are the signs and symptoms of mast cell tumors in dogs?
Dogs with mast cell tumors may show any combination of the following signs:
- A new mass under, on, or within the skin
- An existing mass that has changed (in size, color, or hair cover)
- Bleeding, swelling, redness, and/or itching of an existing mass
- A mass that gets bigger, then smaller, over 24 hours
- Facial swelling or hives
- Unexplained appetite loss, vomiting, and/or diarrhea
If you notice any of the above signs, schedule an appointment with your veterinarian.
How does Embark determine genetic risk for mast cell tumors in dogs?
Powered by data from millions of dogs, our research team developed a novel genetic model that estimates a dog’s relative risk for developing mast cell tumors. It combines genetics and Embark’s owner-reported research data to generate a risk estimate for both single-breed and mixed-breed dogs.
Our scientific model for MCT risk is unique, offering the first cancer-related risk assessment of its kind from a dog DNA company. To be clear, it’s not a diagnostic test, but rather a predictive tool that can inform how veterinarians and pet owners provide interventional care for dogs who may be at risk of developing MCT in the future.
Embark Breed + Health Test
$199
Embark DNA Test for Purebred Dogs
$199
How are mast cell tumors diagnosed?
In almost all cases, mast cell tumors can be diagnosed accurately with a fine needle aspirate (FNA), which uses a thin needle to take a sample of the tumor. If needed, analysis of a larger tissue biopsy is used to determine the grade of the tumor, which helps to inform prognosis and treatment options.
Depending on the situation, your veterinarian may recommend additional tests, including imaging and a needle aspirate of the lymph nodes and abdominal organs, to determine if the tumor cells have spread. Other tests, like bloodwork and urinalysis, may also be used to check for secondary effects of the tumor spreading or to determine which treatment options might be appropriate.
How are mast cell tumors treated?
For tumors found under, in, or on the skin, surgical removal is a common treatment. More recently, treatment with injectable medications has been approved to address the tumors. Your veterinarian can recommend the best course of action for your individual dog.
Mast cell tumors tend to invade the tissues around them, which means that the surgeon will remove a wide surgical margin (area of healthy tissue around the tumor) to make sure all the local cancerous cells are removed.
Before surgery, your veterinarian might recommend additional or alternative treatment to help manage the tumor and relieve the associated side effects.
If surgery is not an option, if the tumor is likely to spread, or if the skin tumor is small, your veterinarian may recommend treatments like chemotherapy, radiation therapy, or a drug injection directly into the tumor. Your veterinarian may also recommend a consultation with a veterinary specialist in oncology or surgery.
What to do if your dog is at increased risk for mast cell tumors
Whether your dog’s Embark results show elevated risk or you just want to be proactive, the single most important thing you can do is monitor. Make regular body checks a part of your dog’s routine — feel for new lumps and bumps and monitor old ones.
Make an appointment with your veterinarian if:
- You notice a new mass in, on, or under their skin
- An existing mass has changed in size, color, or hair cover
- A mass is painful or has started bleeding
- Your dog has signs consistent with an allergic reaction (such as hives)
- Your dog has undiagnosed gastrointestinal signs like vomiting or diarrhea, especially if they contain red or black (digested) blood
Learn more about the preventive steps you can take with Embark veterinarian Dr. Kari Cueva.
