Mast cell tumors in dogs are the No. 1 most common skin tumor in dogs, according to the American College of Veterinary Surgeons. But what exactly is a mast cell tumor, what are the signs of mast cell tumors in dogs and how are these tumors treated?
Causes of Mast Cell Tumors in Dogs
Mast cells themselves aren't cancer cells. As the National Cancer Institute explains, they're a type of white blood cell, though they aren't normally found in the blood. They originate in the bone marrow and are found throughout the body's various tissues. Mast cells are normally involved in a number of functions in your dog. They play a role in inflammation, allergic responses, parasite presence responses, and even necrosis and the breakdown of dead tissues.
Unfortunately, sometimes things go awry. For reasons veterinary scientists don't yet understand, mast cells sometimes mutate and multiply in masses, going against the normal cell life cycle that keeps their numbers in check. This unregulated growth results in a mast cell tumor. These tumors can occur in dogs of all breeds and ages.
Clinical Signs of Mast Cell Tumor in Dogs
Mast cell tumors in dogs can vary in appearance, but they're usually in the form of a lump. These lumps can occur on the skin, muzzle, mouth, genitals or even inside the body on the organs.
When you're petting or examining your dog, you may notice a firm lump tightly adhered to the skin or a squishy and movable lump under the skin. You may see one or multiple lumps, and they might be ulcerated, oozing or bleeding. The lump may remain the same size, grow rapidly or even recede, but that doesn't make it any less dangerous.
Diagnosing Mast Cell Tumors in Dogs
Lumpy, bumpy, raised, flat, loose, squishy, firm, big or small — each and every lump on your dog should be evaluated by a veterinarian.
Your vet will need to perform a diagnostic test called a fine needle aspiration to collect a small sampling of cells from the tumor. Luckily, this test is fast and minimally invasive, and it can usually be done following the initial examination. However, some tumors don't shed many cells during this test, or the sample may not be representative of the whole lesion. So, though this test is a great starting point, your vet may recommend a punch biopsy, as it allows a more comprehensive examination of the mass's architecture. With a biopsy, a microscopic examination of the tissue (histopathology) is sent out to a specialized laboratory for a veterinary pathologist to prepare and evaluate.
After a mast cell tumor diagnosis, your vet may recommend additional diagnostics such as bloodwork, chest radiographs (X-rays) and an abdominal ultrasound to determine whether the tumor has spread to other locations (known as metastasis). A fine needle aspirate of a local lymph node may also be recommended.
Tasty Tips
Mast Cell Tumor Treatment
To determine the best treatment for a mast cell tumor, an expert reading from a board-certified veterinary pathologist is necessary. All recommendations for cancer treatment in dogs require a pathologist to determine the stage, or extent, of the cancer. Mast cell tumors are graded from I to III, with I being the least aggressive and III being the most advanced. The other diagnostics (X-rays, lymph node aspiration, bloodwork and imaging as needed) allow the pathologist to formulate a top-notch treatment plan.
Depending upon the report, the pathologist may recommend surgery, with or without chemotherapy. After surgery, the mass should be sent in for a report again to ensure that all the cancerous cells were removed and clean margins (meaning there aren't cancer cells at the outer edge of the tissue) were obtained, which isn't always possible. Note that while surgery and chemotherapy are often recommended for tumors in grades II and III, you can also discuss less aggressive approaches aimed more at comfort care at any stage with your vet and/or veterinary oncologist.
Life Expectancy for Dogs With Mast Cell Tumors
It is difficult to predict a single life expectancy for dogs who develop mast cell tumors, as it varies depending on many factors. If the tumor is limited to the skin with no evidence of metastasis and surgical removal achieved clean margins, the prognosis can be quite good. For tumors that are scored a grade II or III, the prognosis may not be as good. Furthermore, tumors in locations such as the mouth or genitals often lead to a more guarded prognosis.
The good news is that early diagnosis and treatment improve the prognosis of mast cell tumors, making it important to regularly examine your dog at home. This can be done simply with observational petting and intentional at-home exams. Remember to schedule a veterinary visit should you discover any new masses on your dog.
Related products
Hill's Science Diet Adult 7+ Small Bites Chicken Meal, Barley & Rice Recipe Dog Food
Supports energy level & beautiful coat. Helps keep immune system, heart & kidneys healthy
Hill's Science Diet Adult 7+ Small & Mini Chicken & Brown Rice Recipe Dog Food
Supports energy level & luxurious coat in Small & Mini dogs. Helps keep immune system, heart & kidneys healthy.
Hill's Science Diet Adult Small & Mini Chicken & Barley Entrée Dog Food
Chicken & Barley recipe with precisely balanced nutrition to keep adult dogs active and healthy.
Hill's Science Diet Adult Light with Liver Dog Food
Low calories & L-Carnitine help promote ideal body weight, support healthy mobility & maintain heart function
Hill's Science Diet Adult Small & Mini Savory Stew with Beef & Vegetables Dog Food
A delicious complement to the nutrition of Science Diet Small Paws dry dog food
Hill's Science Diet Adult Small & Mini Beef & Barley Entrée Dog Food
Beef & Barley recipe with precisely balanced nutrition to keep adult dogs active and healthy.
Hill's Science Diet Adult Large Breed Lamb Meal & Brown Rice Recipe Dog Food
Supports healthy joints, lean muscle, and beautiful coat for large breed dogs
Hill's Science Diet Adult 7+ Healthy Cuisine Roasted Chicken, Carrots & Spinach Stew Dog Food
Delicious roasted chicken paired with tender vegetables in a succulent stew
Hill's Science Diet Puppy Large Breed Lamb Meal & Brown Rice Recipe
Vital nutrients to support 5 essential building blocks for lifelong health
Hill's Science Diet Adult Oral Care Chicken, Rice & Barley Recipe Dog Food
Clinically proven kibble technology to reduce plaque & tartar build-up
Hill's Science Diet Adult 6+ Large Breed Chicken Meal, Barley & Rice Recipe Dog Food
Supports energy & beautiful coat. Helps keep immune system, joints, heart & kidneys healthy
Hill's Science Diet Adult Perfect Digestion Salmon, Whole Oats, and Brown Rice Recipe Dog Food
Science Diet's breakthrough nutrition supports ultimate digestive well-being & healthy microbiome
Hill's Science Diet Adult Sensitive Stomach & Skin Chicken & Vegetable Entrée dog food
Supports digestive health, nourishes skin and promotes a lustrous coat
Hill's Science Diet Adult Perfect Weight Chicken & Vegetable Entrée Dog Food
Over 70% of dogs lost weight within 10 weeks when fed this nutrition
Hill's Science Diet Adult Salmon & Brown Rice Recipe Dog Food
Supports healthy immune system, digestion, lean muscle & beautiful coat
Hill's Science Diet Adult Sensitive Stomach & Skin Small Bites
Hill's Science Diet Sensitive Stomach & Skin dry dog food is gentle on stomachs while nourishing skin & promoting a lustrous coat. In a delicious small bite size
Hill's Science Diet Adult Small Bites No Corn, Wheat, Soy Chicken & Brown Rice Recipe dog food
Supports healthy immune system, digestion, lean muscle & beautiful coat
Hill's Science Diet Adult No Corn, Wheat, Soy Savory Stew with Beef & Zucchini dog food
Hill's Science Diet Adult 7+ Healthy Cuisine Hearty Beef, Carrots & Peas Stew Dog Food
Delicious braised beef paired with tender vegetables in a succulent stew
Hill's Science Diet Adult Salmon & Barley Entrée Dog Food
Supports healthy immune system, digestion, lean muscle & beautiful coat
Related articles
Does My Dog Have a Bruise?
If you've noticed an odd bump in your dog's skin, you may wonder if it's a bruise or something more serious. Learn what could be causing this type of issue.
Best Dog Breeds for Hot Weather
If you live in a warm area and are thinking of adopting a dog, you might be wondering "what are the best dog breeds for hot weather?"
Dog Tail Signs: What That Wagging Means
Learn how to tell what your dog is feeling from his tail wagging, including what mood he might be in based on the motions and speed of his tail.
Adopting Dogs for Seniors: Tips for Finding the Perfect Companion
Learn more about how dogs for seniors are loyal companions. They are pack animals who want nothing more than some attention, activity, and love.
Xylitol and Dogs: A Harmful Combination
The sweetener xylitol can be harmful to dogs. Discover which food products contain xylitol, signs your dog has consumed some, and what to do in that case.
Is My Dog Sick? How Can I Tell?
If your dog is behaving strangely and you suspect something is wrong, learn some common behaviors they may be exhibiting to show they're not feeling well.
Parvovirus: What You Need to Know
Parvovirus in dogs, especially puppies, is a devastating illness that can be fatal. Learn the facts about parvo & what to do if your dog has been exposed.
Chondrodystrophic Dog Breeds: All About Short-Legged Dogs
All About Chondrodystrophic (Short Legged) Dog Breeds
What Does Dog Pointing Mean?
Why do dogs point? Discover what your dog is telling you with his nose and which breeds are naturally suited for training to point.
Dog Eye Boogers, Goop & Gunk: When Should You Be Concerned?
Learn about dog eye boogers, goop, gunk & crustiness: when it's normal vs. when it could be a health concern and which breeds & sizes are most susceptible.
Service Dogs Helping Other Dogs: Two Real-Life Stories of Pups Helping One Another
While service dogs play a huge role in helping people, they can also help other dogs with special needs. Read two true stories of these remarkable dogs.
Helping Your Dog Cope With Thunder & Anxiety
Find out how to help your dog get over his fear of thunder by learning what to do and not do during thunderstorms.
Special Diet Needs for Large & Giant-Breed Puppies
Large and giant breed puppies have different nutritional needs than other dogs. Learn how to provide the special care they need to grow up big and strong.
Managing Your Dog's Seasonal Allergies
Seasonal allergies can affect dogs just like humans, but with a few preventative measures & testing or medicine, you can get these issues under control.
Why Is My Dog Eating Dirt?
Dogs eating dirt: it can be a random occurrence or a regular thing, so learn what to do if you notice this behavior and if you should visit the vet.
Dental Disease in Dogs: Symptoms & Treatment
Discover what dental disease means for dogs, and how you can be treating oral health issues by simply feeding your dog food with proper nutrition.
Health Hazards of Excessive Salt for Your Dog
Understand the importance of salt in your dog's diet, as well as the risks associated with excessive salt intake.
My Dog Was Sprayed By A Skunk: What Should I Do?
Learn what to do if your dog gets sprayed by a skunk, including determining where they were sprayed and tips for getting the skunk smell off of your dog.
Hill's Puppy Food: Quality Ingredients for Health & Nutrition
Learn about Hill's puppy food and the nutritional benefit & high quality ingredients that it contains for your pup.
How to Treat A Cut on A Dog (& What to Put on It)
Learn basic steps & precautions for treating a cut on your dog, including what you can put on the cut, and when you should take them to the vet.
Put your dog on a diet without them knowing
Our low calorie formula helps you control your dog's weight. It's packed with high-quality protein for building lean muscles, and made with purposeful ingredients for a flavorful, nutritious meal. Clinically proven antioxidants, Vitamin C+E, help promote a healthy immune system.
Put your dog on a diet without them knowing
Our low calorie formula helps you control your dog's weight. It's packed with high-quality protein for building lean muscles, and made with purposeful ingredients for a flavorful, nutritious meal. Clinically proven antioxidants, Vitamin C+E, help promote a healthy immune system.