When I found a seemingly innocent-looking lump on my Cocker Spaniel’s shoulder blade, I was shocked to receive a mast cell tumor diagnosis. If you are reading this post, your dog has likely been diagnosed with a mast cell tumor or you want to learn more about mast cells and what causes these tumors.
Often dubbed the “great imposters,” canine mast cell tumors can look like an ordinary lump, wart, or growth on a dog’s skin, but they must be addressed as soon as possible. If you have a dog with mast cell tumor (MCT) as a confirmed diagnosis, there are several options. When MCTs appear on a dog’s skin, they vary immensely in appearance. They can be raised on top of the skin or be red, ulcerated, and swollen.
Prognosis and treatment of mast cell tumors include surgery, radiation therapy, chemotherapy, drug therapy, and/or a new form of treatment called Stelfonta, an intratumoral treatment for this very common form of skin cancer in dogs. Lumps and bumps on dogs are very common, and no one, including veterinarians, can diagnose a dog lump without aspiration or biopsy.
Cancer is a scary six-letter word, and millions of dogs are diagnosed every single year. Since mast cell tumors vary widely in their size, shape, appearance, texture, and location, it is important to be the aggressor and not let cancer take hold of your dog.
In this article, I’ll share my dog’s journey with a mast cell tumor along with survival tips, what the experts say, how mast cell tumors are diagnosed, and the latest innovations and treatments to help your dog.
My Dog’s Journey With A Mast Cell Tumor
“Come home quick, Brandy’s lump is bleeding,” my wife called me at work to flip my day upside down.
Cancer. I will never forget my Cocker’s Spaniel’s veterinarian calling me to tell me my dog had a mast cell tumor and we needed to get aggressive about treatment. It all started with a small wart-like lump on her right shoulder blade, which appeared within two weeks after then-yearly vaccinations.
My dog’s veterinarian at the time tried to “squeeze” the lump and said it was probably nothing more than a pimple or sebaceous cyst. He was dead wrong. The C Word. You could have knocked me over with a feather.
An emergency veterinarian (and a second opinion) were summoned to examine Brandy’s “bleeding lump.” After laser excising it, initial reports showed cancer, with an outside laboratory confirming a stage II mast cell tumor.
Brandy was my first Cocker Spaniel and her mast cell journey included:
- Laser surgery showed clean margins so a second procedure was not needed.
- Abdominal ultrasounds to check for metastases every three months for one year and then every six months in year two at Cornell University’s Oncology Department. Our vet and oncologist wanted to be sure the mast cells did not spread to the liver or spleen, and an abdominal ultrasound would show this.
- Buffy coat bloodwork
- Regular measurement and aspiration or biopsy of all new lumps and bumps
What Is A Canine Mast Cell Tumor?
Mast cells develop from cells within the immune system. They are found in connective tissue and carry histamine and heparin in small granules. Humans have mast cells, too.
If a dog has an allergic reaction, mast cells get to work. Think of when a foreign invader comes at the body: Histamines flare up and the mast cells serve to modify the immune reaction. Just like other cells in the body, mast cells can divide rapidly and form a tumor. Mast cell tumors are one of the most common types of skin cancer in dogs.
According to the Michigan State University Veterinary Diagnostic Laboratory, it is not yet known why MCTs are more prevalent and malignant in dogs versus other animal species.
Sometimes MCTs will bigger and smaller due to the histamine getting released into local tissues and getting reabsorbed. Since heparin can get released as well, MCTs can bruise since heparin is a blood thinner. So if a growth appears on your dog’s skin, be sure not to wait and see the veterinarian. MCTs can be tricky!
What Do Mast Cell Tumors Look Like?
Mast cell tumors look like anything and everything. Dr. Sue Ettinger, the “Cancer Vet” says MCTs account for 15 to 20 percent of all skin cancers in dogs. Some MCTs are very benign despite their malignant nature and others are much more aggressive. Dr. Sue calls them “treatable tumors,” and this is something to remember as your dog faces treatment.
MCTs can have a variety of appearances. Washington State University’s Oncology Service says MCTs can look like just about anything from a benign-appearing lipoma to an angry-looking mass with thickness.
What To Do If You Find A Lump On Your Dog
An oncologist at Cornell gave me a rudimentary diagram of a dog and told me to chart Brandy’s lumps. After a few years, I could have connected the dots.
Here’s what to do if your dog has a new lump or bump:
- If a lump occurs, see your vet. When Brandy had a few lipomas (warty growths), I had them all removed when she was under anesthesia for something else. Cockers tend to have more sebaceous oil in their skin than other breeds, so lumps are somewhat expectant.
- Photograph each new lump and keep the image safe and secure. Be sure to note EXACTLY where it is located on the dog’s body. When you write “ear,” that might not make a lot of sense if more lumps develop.
- Invest in calipers. I got mine at a hardware supply store back in the 1990s. These days, you can get calipers on Amazon or digital calipers from Dr. Sue Cancer Vet’s website. Calipers minutely measure the width of a lump. Document it. Monitor the lump for any sign of growth or physical change. See the veterinarian.
- Document any changes, new lumps, and locations on the body in our DogMinder Canine Health & Wellness Journal.
- DON’T squeeze any lump or bump on a dog’s skin, as this can lead to infection and is a generally bad idea.
- DON’T panic. Out of over 25 aspirations in her lifetime, ONE turned out to be cancer. One too many, but we caught it.
- Print copies of skin maps and document each new growth and location.
- Know the warning signs of canine cancer.
How Are Mast Cell Tumors Diagnosed In Dogs?
A true diagnosis can never be confirmed without diagnostic evaluation through a fine-needle aspiration or a biopsy of the suspicious mass. Even after many benign aspirations, any new mass can be malignant. Early detection is crucial.
Some vets will rush and want to remove a mass right away, which is not always a viable option. Many veterinary oncologists agree that aspiration is generally advised before a mass is removed. If the mass is not an MCT and turns out to be something even more aggressive, you’ll have a baseline diagnosis and can proceed with a plan.
Dr. Sue Ettinger is a practicing veterinary cancer specialist and says, “No, not even the most experienced veterinarian can look at or feel a mass and know if it is cancer or not. Your veterinarian must perform an aspirate or biopsy to make an accurate diagnosis.”
Pros of Fine Needle Aspiration
- Performed in office
- Quick test
- No need for sedation or hospitalization
- Helpful in diagnosing the type of growth (i.e. mast cell, lipoma, cyst)
Drawbacks of Fine Needle Aspiration
- FNA cannot ascertain if cancer has spread to other areas of the body
- Very occasional inconclusive or incorrect diagnosis with fine needle aspiration
How Serious Are Mast Cell Tumors?
Mast cell tumors are divided into three grades. with grade I being the least aggressive and least likely to spread to other organs. Grade III is considered a highly aggressive MCT with a high likelihood of metastasizing to other organs.
Grade II MCTs tend not to metastasize, although they can. My Cocker Spaniel’s grade II mast cell tumor never spread to her other organs. In the event of spread, MCTs tend to affect the liver, spleen, bone marrow, and regional lymph nodes.
MCTs are a form of cancer, so they are serious and should be examined and treated as deemed necessary according to the grade, prognosis, and overall health and well-being of the dog.
A new two-tiered histologic grading system has been established in recent years. According to the two-tiered system, high-grade mast cell tumors are significantly associated with shorter time to metastasis or new tumor development and with shorter survival time. It’s called the high-low grading system and has improved the way mast cell tumors are graded.
What Are The Symptoms Of A Mast Cell Tumor?
Many times a dog will have no symptoms of mast cell tumor, but symptoms can be dependent on the grade and location of the tumor. Some symptoms include but are not limited to:
- Tumor on or under the skin which may or may not appear to change in size
- Possible lymph node enlargement
- Loss of appetite
- May be a single growth or multiple masses throughout the body
- May resemble an insect bite, wart, allergic reaction, or innocent-looking growth
- May appear red and angry with fluid build-up
- Tends to occur in middle-aged and older dogs (per Dr. Sue Ettinger)
Causes and Prevention Of MCTs In Dogs
What causes MCTs in dogs?
Like most tumors, the exact cause is not known. About one-third of dogs have a genetic mutation in a protein called the c-kit oncogene. Unlike skin cancer in humans, which is often associated with sun exposure, studies have found no link between sun exposure and MCT in dogs. But chronic inflammation of the skin may predispose dogs to develop MCT, as can the repeated application of skin irritants.Dr. Sue Ettinger
My Cocker Spaniel’s mast cell tumor appeared at the site of her vaccinations. She received her then-yearly vaccines, and the vet gave her multiple vaccines in one spot (not the rabies vaccine). There is something called vaccine-associated sarcoma.
Brandy was firmly diagnosed with a mast cell tumor, grade II, at the site of her vaccine injections.
Certain breeds of dogs are more highly represented than others, and the University of Penn cites Boston Terriers, Boxers, Pugs, Bulldogs, and Retriever breeds. However, any dog whether purebred or mixed breed can develop MCTs.
One of the best ways to ensure your dog remains a loving, loyal part of the family for a long time is to touch him or her. 10 touches, 10 minutes, once a week will keep a dog healthy, happy, and rewarding you with love. Learn more about 10 touches to keep a dog healthy.
Dedicated dog mom Nancy B. of Maryland regularly runs her fingers through her Cocker Spaniel’s coat on a regular basis. She touches Mayor’s skin and examines his body, armpits, belly, and gives him a thorough “once-over.”
Thanks to Nancy’s due diligence, twice she found small lumps on her dog and twice they have been removed. Mast cell tumor was the diagnosis both times, and surgery was curative for his stage II tumors.
Can Lipomas Become Mast Cell Tumors?
“In general things like lipomas don’t morph into mast cell tumors,” according to Dr. Ettinger.
Some lipomas, she says, should be removed. For example, if a lipoma hinders mobility, is located in an armpit and becomes ulcerated, or if the dog licks at it. Once a lipoma grows larger, it can become challenging.
She says if a veterinarian aspirates a lump and confirms it is a lipoma at 3-cm, but perhaps six weeks later the lump doubled in size, it’s time for a return visit. She recommends having the vet biopsy the lipoma, as cytology isn’t always perfect.
How Are Mast Cell Tumors Treated?
Once a fine-needle aspiration or biopsy has confirmed the diagnosis, treatment for MCTs includes surgery, radiation, chemotherapy, drug therapy, or Stelfonta, a new FDA-approved intra-tumoral injection for the treatment of non-metastatic cutaneous mast cell tumors and non-metastatic subcutaneous mast cell tumors located at or distal to the elbow or the hock in dogs.
Wide margins of normal tissue must be excised around the to increase the likelihood that the tumor is completely removed. Surgical removal is a staple treatment for many canine mast cell tumors. Periodic monitoring is key for dogs with low-grade to intermediate MCTs for which surgery is curative.
If mast cell tumors are unable to be completely resected, could not be removed, or are not amenable to treatment with Stelfonta, radiation therapy is often performed. Sometimes a second surgical procedure is performed.
Radiation or Chemotherapy
Dogs with more aggressive tumors, such as grade III, may undergo chemotherapy. The Washington State Veterinary Teaching Hospital’s Oncology Service says mast cell tumors are unpredictable with their reaction to chemotherapy.
If the pathologist or veterinary oncologist chooses to have an MCT prognostic panel performed, results will show if there is a mutation in a gene called c-Kit. Dogs may be eligible for targeted drug therapy with Palladia (toceranib phosphate) and Kinavet-CA1 (masitinib mesylate).
According to Dr. Ettinger, Stelfonta is injected directly into the mast cell tumor. Although this treatment won’t fully replace surgery to remove MCTs, Dr. Sue loves having Stelfonta as one of the tools in her MCT toolbox.
The success rate thus far has been promising, with a 75-percent response at day 28 after one injection. If a second injection is needed, the response rate goes up to 85 percent. At one year, 88 percent of treated dogs are disease-free. This is an exciting treatment that you can learn more about here:
What About Antihistamines To Treat Mast Cell Tumors?
I asked Dr. Patrick Mahaney, a University of Pennsylvania-trained veterinarian and Certified Veterinary Acupuncturist (CVA), if he knows of any pet parents who use antihistamines as a preventative option for MCTs.
“I’ve had patients take antihistamines once they’ve been diagnosed, but not before as a potential MCT preventative,” Mahaney says. “Antihistamines and steroids can be used to control inflammation associated with MCTs and potentially keep them from degranulating.”
When an MCT degranulates (loses granules as part of an immune reaction), a variety of chemicals having effect to dilate blood vessels, reduce blood pressure, the movement of white blood cells, and have other effects are released into tissues adjacent to the MCT and into the blood stream. Effects of MCT degranulation can be mild to life-threatening.
Additionally, taking nutraceuticals (supplements) containing natural anti-inflammatory substances, like Omega Fatty Acids (Omega 3 and 9), turmeric, ginger, phycocyanin (blue-green algae extract), and others can help to reduce the overall level of inflammation.
He says putting a dog on antihistamines during allergy season is typically fine provided the dog isn’t having any side effects and if the use of antihistamines helps in some capacity.
Dr. Ettinger says since histamine is in the mast cell tumors, the growths may appear red and inflamed as they grow on a dog’s skin.
“If a dog has a really big mast cell tumor, before surgery we will recommend that they go on an antihistamine,” she says.
For dogs with an MCT that cannot be removed, if radiation or chemo are used, she will keep them on an antihistamine. The reason she does this and may include an antacid like famotidine or omeprazole is the histamine causes increased stomach acidity and stomach upset.
She does not use antihistamines and antacids as a preventative, as there is no literature to her knowledge that using them will help prevent mast cell tumors.
What Is My Dog’s Prognosis?
Dr. Ettinger says mast cell tumors are treatable. Each requires different intensities of treatment depending on the grade. If the MCT is low grade and treatment is successful, she will usually see the patient once every three months for a while and then once every four to six months for life for screening.
If the tumor is a grade III and has spread to internal organs, she often sees the patients doing well after a year. She equates the one-year anniversary to a human cancer patient who is given a five- to seven-year survival prognosis. Like people, each dog is different.
We raise our sparkling water dish in a wish that your dog lives a life free of lumps and bumps. If your dog faces cancer at any point, be diligent and don’t panic. As your dog’s advocate and best friend, be the person your dog knows you are.