Mastocytoma in Dogs


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If a dog has been diagnosed with mastocytoma, it means that they have a cancerous nodule or accumulation of mast cells. This is very similar to a tumor, but mast cells are cells that come from the body. An accumulation of these cells is usually the result of trauma, which then becomes cancerous. Mastocytoma is seen in many animal species, including humans. In this guide, we will cover everything you need to know about this canine cancer, including:

  • What is Mastocytoma in Dogs?
  • What Causes Mastocytoma?
  • How is Mastocytoma Diagnosed?
  • What Treatments Are Available for Mastocytoma?
  • How Can I Prevent Mastocytoma in My Dog?

By the end of this guide, you should have a thorough understanding of what mastocytoma is, and how to approach treatment if your dog has been diagnosed with this cancer.

What is Mastocytoma in Dogs?

In order to understand what mastocytoma is, let’s first talk about what mast cells are.

Mast cells are cells that come from the body’s connective tissue and bone marrow. Anything like blood vessel tissue, nerve tissue, and other types of connective tissue are all considered mast cells. Mast cells exist to help defend the body against outside infestations, to help repair tissues, and to help form new blood vessels.

When you have an allergic reaction to something, the mast cells are the cells that are usually responding by swelling or becoming itchy. That is because they are the cells that contain histamine, the chemical that causes allergic reactions.

Now, mastocytoma means that a dog’s mast cells have formed a cancerous tumor. This build-up of cells is graded from not very severe or even benign (Grade 1) to extremely serious (Grade 3). The more that the cancerous mast cell looks different from a normal mast cell, the lower the grade – that is because when it’s easy to identify the cancerous cells, it’s far easier to target and remove them. If the cancerous cells are harder to differentiate from normal mast cells, it will be harder to get rid of them, and the body won’t be as likely to attack them with the immune system.

Mastocytoma is typically seen in the spleen, liver, or the lymph nodes, although it can be found anywhere on or in the body. It can grow and spread very quickly, or it can be a very slow process. In other cases, mastocytoma can simply seem to spring up overnight.

What Causes Mastocytoma?

The short answer is that we don’t know what causes mastocytoma. There are theories, but like most cancers, it seems to be a combination of uncontrollable things, like genetics, rather than any one specific behavior or incident.

Some dogs are genetically predisposed to developing mastocytoma, especially Boxers, Bulldogs, Pugs, and Boston Terriers – all dogs with shortened muzzles. One theory is that these breeds commonly have issues with inflamed skin, and that could be related to the development of mastocytoma.

We do know that mastocytoma tends to develop in older dogs more than younger dogs, with the average age for being diagnosed around eight years old. There are studies that may indicate that changes in reproduction hormones could be responsible for mastocytoma, but these studies have not been confirmed. However, about 50% of the surface-area nodules that are seen with mastocytoma develop in the area between the anus and the sexual organ on a dog, which may indicate that the study has some truth behind it. Other surface-level nodules are typically found on the paws or the neck.

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Mastocytoma in Dogs

What Symptoms Are Often Seen with Mastocytoma?

The symptoms of mastocytoma can vary wildly. They may include:

  • Lesions on the skin
  • Balding spots
  • Inflamed areas on the body
  • Vomiting
  • Inability to eat
  • Tar-like stool or bloody stool
  • Enlarged organs, especially the liver and spleen
  • Enlarged lymph nodes
  • Itchy lumps
  • Diarrhea

The presence of the nodules on the skin is the most common symptom, and they may cause a dog to drag their bottom on the ground, bite or chew their paws, or scratch at their neck constantly.

How is Mastocytoma Diagnosed?

In order to diagnose mastocytoma, the vet will first want to get a thorough overview of your dog’s medical history. This can help them rule out the many other illnesses that could also cause these symptoms to show up. Another important reason for getting all of this information is that the symptoms you see could help the vet determine what areas of the body are being harmed by the cancer. Issues with stool could indicate problems with the liver, for example. This tells the vet where they should focus treatment first.

After this procedure, the vet will take a sample of cells from the growths, and perform some tests to determine if there is an abnormal amount of mast cells for what there should be. This may involve a biopsy of the tissue to learn what grade the mastocytoma is, or the vet may take a sample of fluid from the lymph node, or a sample of bone marrow, to test as well. In some cases, ultrasound images are also taken of the chest and abdomen to help identify if there are growths internally as well.

Bloodwork and urine samples are also usually part of the diagnostic process. With all of this information, the vet can tell:

  • If your dog has mastocytoma
  • How serious the mastocytoma is already
  • What parts of the body are being attacked by the mastocytoma
  • Where treatment should begin

Be sure to keep track of how soon you saw symptoms and how quickly the symptoms grow worse. This information is important for helping your vet make a proper diagnosis and determine the right treatment.

What Treatments Are Available for Mastocytoma?

If the mastocytoma is a lower grade, it isn’t likely to spread throughout the body. However, a high-grade mastocytoma could spread throughout the entire body if treatment isn’t aggressive. There are several ways to treat this cancer.

The first option is usually surgical removal of the nodules that are on the surface. It’s important to get rid of the cancerous cells to stop them from spreading. Radiation therapy may be performed in conjunction with surgery, and it may take more than one round of either surgery or radiation to get the cells completely out of the body.

If the mastocytoma is of a higher grade, chemotherapy may be another option. Steroids and traditional chemo drugs are all part of a treatment plan that can be used for dogs. If the mastocytoma has affected an entire limb, amputation could also be an option to stop the spread to the rest of the body. The entire goal of treatment is to remove the mast cells or to stop them from spreading to the rest of the body if removal is not the best option. If it’s a choice between having a dog with no tail, or only three legs, or a dog suffering from cancer, most pet owners would likely choose the amputation.

Your dog will also likely need treatment to manage the symptoms while going through the surgery, radiation, or chemotherapy process. This may mean:

  • Taking a steroid to help kill the cancerous cells.
  • Taking antihistamines to stop the dog from itching.
  • Taking medications to prevent diarrhea or vomiting.
  • Switching to an immune-boosting diet or taking supplements to aid the immune system.
  • Having fluids administered to the dog.
  • Having food fed to your dog through a tube if they can’t keep solid food down.
  • Taking an antacid or other medication to stop the urge to vomit.

Overall, whether your dog will make it through mastocytoma or not largely depends on many things. If the mastocytoma was a low-grade mastocytoma and was caught very early, and the surgery or radiation therapy was successful, then yes, your dog will likely survive just fine. If the cancer isn’t detected soon enough, or if it is a very high-grade cancer that has spread all over the body, or if the dog simply doesn’t respond to the treatments, it could be a life-threatening cancer.

During the treatments and after, your dog will need to be monitored by the vet. They will do frequent blood counts to watch how the presence of cancerous mast cells are being impacted by the treatments. Your vet will also want to evaluate new modules or masses if they appear to ensure that the cancer is not spreading. This management program will likely last for many months after the initial treatment to ensure that your dog is truly out of danger.

How Can I Prevent Mastocytoma in My Dog?

There is no way to prevent mastocytoma because we don’t know what causes it. What we do suspect causes it isn’t something that we necessarily can fix, such as changes in hormone levels. The best thing you can do for your dog if you are concerned is to ensure that they are staying healthy and are eating a balanced diet that boosts their immune system. Give them supplements to support a healthy immune system as well. This may not prevent a dog from developing mastocytoma if they were going to, but it could help the treatments to be more effective in that case.

Things you can add to your dog’s diet to help boost their immune system include:

  • Fish oil, or an Omega-3 and Omega-6 fatty acid supplement
  • Vitamin E
  • Echinacea
  • Suma root
  • Egg yolks
  • Reishi mushrooms
  • Olive leaf extract
  • Probiotic supplements or plain, unsweetened yogurt

Other things you can do to help boost your dog’s immune system include:

  • Keeping your dog’s skin and hair clean
  • Letting your dog be around other dogs frequently
  • Keeping your dog’s life free of stress
  • Avoiding areas where other dogs frequently go to the bathroom
  • Washing your dog’s toys regularly
  • Getting plenty of exercise
  • Getting vaccinations
  • Brushing your dog’s teeth
  • Helping your dog maintain a healthy weight
  • Feeding your dog a meat-first diet
  • Keeping your dog hydrated
  • Avoiding common household toxins like cleaning supplies or certain houseplants

While none of these things really prevent mastocytoma, they can help make your dog healthier so that they can better fight off the cancer should they ever develop it. Having a strong and healthy immune system can be exactly what your dog needs for chemo or surgery to work should they get this type of cancer.

To Sum It Up

Mastocytoma is a type of cancer that all animals, including dogs, can develop. The cancerous cells come from the connective tissue in the body and can spread to all the organs and systems. However, in dogs, it is most common to see mastocytoma on the skin in the form of nodules.

If the mastocytoma is low grade and is caught early, surgical removal of the nodules and radiation treatment can be very effective. If the mastocytoma is a bit more advanced or was caught later, chemotherapy may be another option. However, because we don’t know much about the causes of mastocytoma, we don’t really know how to prevent it.

Dogs that continue to develop nodules or lesions after the surgery to remove the initial mastocytoma typically don’t survive the first year. That is why it is so vital to have your dog checked out if they exhibit any of the symptoms discussed in this guide.

The Final Word

Mastocytoma is surprisingly under-studied considering how prevalent it can be. We still don’t know what causes it, which leads to a lot of trouble trying to decide how to prevent it. Unlike other human cancers, where we can say things like “give up smoking to drastically improve your chances of not developing lung cancer”, we just don’t know what to say for mastocytoma. It can be a mild issue that is taken care of in one surgery, or it could be devastating. The important thing is to ensure that you take your dog to the vet if you see any of these symptoms. The sooner you get to the vet, the better the outcome will likely be.

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