All dogs develop odd lumps or small bumps at some point, whether due to an allergy or an injury, but not all lumps and bumps are harmless. Some types of masses may be cancerous, such as mast cell cancer.
Cancerous mast cell tumors, or MCTs, are sneaky invaders that spread quickly if left untreated. In addition to its growth, a mast cell tumor releases large amounts of histamine that are disruptive and can become life-threatening.
If your dog has mast cell cancer, I provide detailed guidelines based on the latest research to help you give your pet the best chance. This guide covers new treatments, such as intratumoral injections, along with the importance of a low-histamine diet and
Understanding Mast Cell Tumours (MCTs) in Dogs
Mast cells are actually immune cells that you’ll find in humans and animals. So how do mast cells become cancerous? When a mast cell becomes dysfunctional, is exposed to chronic inflammation, or encounters environmental triggers, it can develop into a cancerous mast cell tumor.
How Mast Cell Tumors are Graded
MCTs in dogs are graded according to the severity of the cancer. Your vet will perform a histopathology and grade the tumor based on a three-tier scale known as the Patnaik system:
Grade I
Tumors have a low chance of spreading.
Grade II
Abnormal cells require further investigation.
Grade III
Aggressive cancer cells with a significant risk of metastasis.
Low-grade tumors (I and II) have the best prognosis, with most of these MCTs successfully removed surgically. Grade III tumors have a poor prognosis. My dog Sasha was diagnosed with grade III mast cell tumors at 11 years old. The vet at the time told me that she had less than 3 months; if I was lucky, but miraculously, Sasha almost made it a year. Her leg was very swollen at the end, but with vitamin C therapy, supplements, and lots of love, she gave us more time than what was expected.
How to Identify MCT Symptoms and “Darier’s Sign”
These nasty tumors can be quite difficult to detect because they look like any regular lump or bump that appears on a dog’s skin. Often referred to as “imitators,” mast cell tumors can develop as solid bumps, soft lumps, small pimples, or hairless masses that become ulcerated over time.
It’s important to note that these tumors can change in size. The release of histamine causes swelling and shrinkage within 24 hours. Don’t ignore the nodules or bumps that seem to “come and go.”
In Sasha’s case, her mast cell tumors first appeared as small, solid lumps. The masses that developed thereafter became ulcerated, turning pink and not healing. Despite surgery to remove the tumors, our vet suspected that one had metastasized and was located deep in her hind leg muscle. This led to rapid, severe swelling and was inoperable.
What makes MCTs in dogs so tricky is their reactivity. When touched or scratched, these tumors become angry and release histamine, resulting in inflammation.
One way of telling that a lump or bump is a mast cell tumor is the development of swelling, redness, and itchiness when it’s manipulated. This is called Darier’s Sign. Your dog may constantly lick and bite the affected area. The swelling usually subsides after 24 hours, but it’s best to avoid manipulating these lumps. Don’t massage the mass, thinking it will give your fur friend relief, because it only leads to more irritation.
The Side Effects of Mast Cell Tumors in Dogs
Aggressive MCT’s will produce significant amounts of histamine when interfered with because of a process called degranulation. The tiny granules within the tumor burst when they’re disturbed, and that’s when histamine is unleashed.
Histamine causes chronic inflammation, increasing the risk of stomach ulcers. Many dogs with mast cell cancer pass from ruptured ulcers due to internal bleeding or severe anaphylaxis. It’s not something any of us wants to think about, but early detection could save your pet’s life.
While not all bumps or masses on your pooch mean cancer, it’s important to have a lump or nodule checked by your vet. If it doesn’t go away over a two to three-week period and you notice a fluctuation in size, the lump should be tested. Your vet can perform a quick skin scrape to detect cancer cells or send the sample to a lab for further testing.
Latest Veterinary Treatment Options
The latest veterinary treatments for mast cell cancer in dogs consist of surgery, chemotherapy, and holistic therapy. Let’s take a closer look at the pros and cons of each type of MCT treatment.
Surgery
The gold standard for treating mast cell tumors is surgery. When a mast cell tumor is cancerous and left to grow and metastasize, your options for treatment become very limited. For this reason, I stress the importance of monitoring your pet’s odd lump or nodule. In Sasha’s case, a small bump below her tail transformed in less than a month into an angry and ulcerated mass. Once it was removed, the vet informed us that degranulation had already occurred. Degranulation happens when the tumor becomes inflamed and releases large amounts of histamine. I also struggled to control the bleeding from the wound and had to apply ice packs to the area daily to support healing.
While there are many less invasive treatments, if you can afford it and your dog is healthy enough to undergo anaesthesia, I highly recommend surgical removal of a mast cell tumor. Your veterinarian will try to achieve clear margins, which means that there are no cancer cells in the surrounding tissue. In my opinion, achieving clear margins and placing dogs on a nutritious diet provides the best outcome.
Intratumoral Injection
Another treatment that has been gaining attention is the intratumoral injection, which is a type of immunotherapy. It involves the use of Tigilanol tiglate, otherwise called Stelfonta. This form of therapy relies on the body’s immune response to eliminate the tumor cells. This veterinary treatment only works for very small and non-metastatic or low-grade tumors. This means that the cancer remains within a localized area without spreading to the rest of the body.
The intratumoral injection destroys the cancer cells and offers the benefits of a quick treatment without the risks of anesthesia and surgery. However, when a mast cell tumor is manipulated or “angered,” it releases so much histamine that it places your fur baby at high risk of anaphylaxis.
Furthermore, pets will require a strict regimen of medication to control the histamine as the tumor is slowly destroyed by the injection. Some older and weaker dogs may not cope with the impact of histamine on their bodies. It can lead to significant inflammation, and if your dog picks up a secondary infection, they’ll need additional medical care, including hospitalization. In some instances, the side effects could become life-threatening.
Stelfonta for Dogs Costs
These injections reach up to $1000 per treatment. Be sure to discuss the pros and cons of the intratumoral injection with your veterinarian. Think of your dog’s age and general well-being before moving forward with this treatment. Should they experience an allergic reaction and require hospitalization, secondary treatment will significantly add to these costs.
Immunotherapy – Gilvetmab
Gilvetmab is the latest immunotherapy provided to dogs with mast cell cancer. It is administered intravenously and works by allowing the dog’s immune system to attack the cancer. All three stages or grades of tumors can benefit from this treatment. Because it can shrink tumors, Gilvetmab is most beneficial for inoperable tumors. So, when a tumor is located on the paw, where there is very little skin to cover the wound, this treatment can be very helpful.
Surprisingly, this immunotherapy has an efficacy rate of more than 70%. On the downside, it requires biweekly treatments of up to 10 treatments to manage the cancer. Unfortunately, Gilvetmab is not a cure, and you still have to monitor your pets for the reappearance of the tumor. One must also consider the costs of each treatment, along with traveling to the vet every second week. This immunotherapy will lead to side effects, such as lethargy, poor appetite, and can affect liver function.
Supportive Medications: Antihistamines and Antacids
Mast cell tumors are known to release histamine. The problem with histamine, particularly in high volumes, is that it increases inflammation, causes itchiness (Pruritus), and contributes to the formation of stomach ulcers. Some dogs are affected by heart problems, including drops in blood pressure and behavioral issues, from fatigue to aggression.
To prevent and minimize the effects of histamine, all dogs with mast cell cancer must be placed on antihistamines and antacids. Antihistamines like Benadryl will control the amount of histamine in the body and significantly reduce irritating and potentially life-threatening allergic reactions. Antacids relieve stomach pain, acidity, and reflux associated with ulcers. These medications should not be stopped while your dog is battling mast cell cancer. Many dogs with MCTs pass from a ruptured stomach ulcer, which is a terrible experience.
Essential At-Home Care and Lifestyle Adjustments
When your fur baby is first diagnosed with mast cell cancer, it can feel overwhelming and difficult to deal with. But making a few changes at home will make the biggest difference to your dog’s life in terms of their comfort and longevity. To make things a little easier, I’ve broken down a few simple care strategies for you and your pet.
Avoid Manipulating the Tumor
As previously mentioned, massaging or touching the tumor is a no-go! Don’t try to apply cream to it or bandage it. Simply avoid it, if you can, to prevent the release of histamine.
Dietary Strategies for Dogs with Mast Cell Cancer
Every dog living with mast cell cancer can benefit from a modified diet. The first step is to reduce their daily carbohydrate consumption. This means reducing or replacing kibble or dry food with meat, vegetables, and simple carbs like rice, quinoa, and millet. You can check out my page on the “Dog Cancer Diet” to learn how to prepare protein, along with a list of vegetables that are safe for your fur friend to eat.
In addition to a low-carb diet, dogs with mast cell tumors must be given low-histamine foods. Be sure to feed fresh foods without artificial colors, flavors, and preservatives that may trigger allergies. Incorporate eggs, turkey, chicken, and lamb in addition to veggies such as broccoli and carrots. Do not give your dog canned food or any type of fermented meat. You should also avoid yogurt, which is actually a high-histamine food.
Another important part of at-home care for mast cell tumors is providing your pets with supplements. Products such as omega-3 fatty acids, coconut oil, and vitamin C for dogs will strengthen the immune system, increase energy, and support healing. Vitamin C should only be given in a water-soluble form because dogs cannot digest regular vitamin C.
Consider immune-boosters like turkey tail mushrooms and full-spectrum CBD oil. I gave Sasha THC oil to help with pain and relaxation. The histamine released by the tumor increases restlessness, making it hard for your dog to sleep at night. Using a full-spectrum oil or THC oil will help them sleep and give them a bit of an appetite. If you’re unsure about full-spectrum CBD dosages, benefits, and risks, check out my post on CBD and THC for dogs.
Reduce Stress
A calm environment is always recommended for dogs with cancer. It supports their immune health, and in the case of MCTs, minimizes the possibility of injuring or agitating the tumor. If your dog is still mobile, you can play with them and continue to go on walks, but any strenuous or rough activities should be kept to a minimum to avoid irritating the tumor and releasing histamine.
Caring for Your Dog With Mast Cell Cancer
Just over 20% of all dogs are affected by skin cancer, with mast cell tumors being the most prominent. All I can ask is that once a month, you check your dog for any bumps or nodules by running your hands over their stomach, back, and legs. Check the insides of their ears, and if you spot something, pay close attention. A mast cell tumor can grow rapidly, so have it checked by your vet.
If you’ve noticed changes in the size of the lump, insist on getting it tested with a skin scrape. It’s better to know whether it’s cancerous than to regret not acting while the tumor is small.
It’s not easy caring for dogs with cancer, but I hope that Sasha’s story and the treatments discussed in this guide help you and your fur baby with comfort and supportive care.