Mast Cell Tumor in Dogs: How CBD Can Assist

By Chelsea Hunt-Rivera / November 1, 2018

Finding lumps and bumps on your perfect furry friend can be quite troubling for a dog owner. It’s hard to train our minds to not automatically think the worst. Yet, if you jumped on Google and typed in “lumps on dogs,” you’re probably already in a downward spiral of panic. This is going to sound like an impossible thing to ask… but try to remain calm. Many lumps and bumps on dogs are nothing more than a mole or a minor allergic reaction. However, some lumps, of course, are much more serious than that.

In this article, we will cover everything you should know about mast cell tumors in dogs. It is imperative for pet owners to know how to recognize symptoms of the disease in order to catch it early on and begin treatment straight away. While your dog’s lump may be something that is easily resolved, in some cases, such as mast cell tumors, immediate treatment is imperative. 

Mast Cells: The Basics! 

Before we dive straight into mast cell tumors, there is some basic terminology that it is important for dog owners to recognize in order to fully understand their dog’s disease. Our dogs are trusting us to take the best care of them.  By understanding what is actually wrong with Fido, pet owners can ensure that they are making the best decisions for their wellbeing. 

What Are Mast Cells 

Mast cells are cells that originate in the bone marrow but mature and settle in other tissues. In fact, mast cells are found within all tissues of the body. With that said, MCTs exist in much larger volumes in the skin, respiratory tract, and digestive tract. They are also found in large quantities around the eyes, nose, and mouth. Mast cells contain histamine and heparin and are involved in a number of important functions.

What Do Mast Cells Do 

Mast cells are responsible for a number of incredibly critical functions. They help to provide the body with a defense against parasitic infestations. Additionally, mast cells support the dog’s body in repairing tissues and therefore help promote the healing process. They also play a crucial role in a process known as angiogenesis, or the formation of new blood vessels. 

A type of white blood cell, mast cells also produce antibodies as a part of an allergic reaction defense. Finally, mast cells play a large part in defending the body against harmful, external agents by acting as a protecting barrier. They shield the body from potentially dangerous allergens and inflammation.

As you may imagine, with all of these critical roles, mast cells are not a single cell type. In fact, in the dog’s skin, most MTCs are a highly reactive type.

Tumors in Dogs… What Exactly Are They 

In simple terms, a tumor is the swelling of a specific body part. Tumors typically occur without inflammation and are caused by an abnormal growth of tissue. Tumors are either identified as malignant (dangerous) or benign (noncancerous and usually harmless).

What is Mast Cell Tumor (also known as Mastocytoma in Dogs) 

A mast cell tumor, or MTC, is cancer that develops from mast cells. Mast cell tumors (also known as Mastocytoma) are the most commonly diagnosed skin tumors in dogs. In fact, approximately 1/3 of all dog tumors are skin tumors. Of that one third, roughly 20% are mast cell tumors.

Some mast cell tumors have a low level of malignancy and are relatively harmless to the dog. However, other MTCs have a high level of malignancy. These tumors can be life-threatening is appropriate treatment isn’t initiated in a timely manner.

Mast Cell Tumors: How Do They Affect Fido

As the cancerous mast cell tumors attack the dog’s body, they block the mast cells from being able to fulfill their important, critical roles. As we previously mentioned, mast cells are responsible for things such as inhibiting parasitic infestations, repairing tissues, and producing new blood vessels. Therefore, when mast cell tumors invade, the body is no longer able to protect the dog as it normally would. Additionally, the mast cell tumors can also have negative effects on the dog’s heart rate, blood pressure, and cause a decrease in the overall homeostasis within the body.

Mast cell tumors are considered to be very common in dogs. Therefore, understanding as much as you can about them is incredibly important.

Mast Cell Tumor in Dogs: Where Are They Found

Most often, mast cell tumors are found in the dog’s skin. Again, mast cell tumors are the most commonly diagnosed skin tumor in dogs. However, MCTs can also be found in other places, including the intestines and lungs. Furthermore, even in cases where mast cell tumors originated in the skin, MTCs are known to spread quickly to other organs, typically the spleen, liver, and bone marrow. This ultimately dictates the stage and grade of the mast cell tumor (more on that in a moment). Finally, pet owners should know that the MCTs that develop in the skin’s surface are usually found on the dog’s trunk and limbs. 

What Do Mast Cell Tumors Look Like

Due to the fact that MCTs vary so greatly in appearance, they can often be difficult to detect. Mast cells tumors can develop in differing shapes, sizes, textures, and in a number of different locations. MCTs can also be soft or firm, raised or flat, as well as covered in hair or ulcerated. They tend to start small but can rapidly increase in size. They can also shrink and then quickly grow. As you can see, MTCs can be a challenge to detect and monitor.

Symptoms of Mast Cell Tumors in Dogs 

It is imperative for dog owners to be aware of the symptoms of mast cell tumors. The earlier the MCT is diagnosed, the better the prognosis and life expectancy times.

A Bump or Lump 

It probably goes without saying that the most prominent physical symptom of mast cell tumors is the presence of a lump or bump (a tumor) under the skin. The tumor may have existed for days, weeks, or even months before the owner noticed it. This is largely due to the fact that the tumor may have fluctuated in size, making it more difficult to detect. Furthermore, as we previously mentioned, the tumor may have only existed for a short period of time, but has rapidly grown, seemingly overnight.

It is important for dog owners to know that mast cell tumors (especially in early stages of their development) may resemble warts or insect bites. It is imperative that pet parents closely monitor any new lumps or bumps that they find on Fido. A wart or insect bite will likely resolve itself whereas an MCT will not. 

Another important fact about MCTs is that approximately 50% of them develop on the dog’s trunk. Therefore, pet parents should keep a close eye on any new growths they find in that region.

Redness or Fluid Buildup

Another symptom of mast cell tumors is the presence of redness and/or fluid build up around the tumor. Skin irritation and inflammation are also commonly due to the release of higher histamine levels within the tumor.

Dog Lymph Nodes

Pet parents may also find lymph node enlargement around the area of the tumor. In many cases, the surrounding lymph nodes will be surgically removed as part of MCT treatment. 

Spleen and Liver Enlargement

Your veterinarian will also look for spleen and/or liver enlargement, both of which characterize wide-spread mast cell cancer.

Gastrointestinal Issues

Finally, gastrointestinal symptoms including vomiting, diarrhea, and loss of appetite are often signs that the cancer cells are spreading.

What Causes Mast Cell Tumors to Develop

Even with constant advancements in science that are being made every day, there is still so much about cancer and tumors which remains unknown. When it comes to mast cell tumors, in the majority of cases, the exact underlying cause is undetermined. With that said, scientists do know that MCTs are the result of a cell mutation within the mast cells. The mutation causes the uncontrollable reproduction and growth of the cancer cells, thus resulting in mast cell tumors.

Dog Breeds at Higher Risk of Mast Cell Tumors

Additionally, based on extensive research, experts have also determined that certain breeds are at an increased risk of developing canine mast cell tumors. These breeds include:

  • Boston Terriers
  • Boxers
  • Weimaraners
  • Bulldogs
  • Pit Bull Terriers
  • Rhodesian Ridgebacks

Additionally, mast cell tumors are typically diagnosed in older dogs but have been found in puppies as young as three months old.

With that said, it is possible for any dog of any breed or age to develop mast cell tumors. The aforementioned breeds are simply at an increased risk of the disease.

Mast Cell Tumor Dog Diagnosis

Your veterinarian will likely perform a fine-needle aspiration and cytology in order to accurately diagnose whether your dog has a mast cell tumor.

Fine-Needle Aspiration

A fine-needle aspirate is a rather quick procedure that is done without having to sedate the dog. The veterinarian will perform the biopsy in order to determine whether abnormal mast cells are present. If cancer cells are present, a surgical tissue biopsy will be necessary in order to classify the grade and stage of the tumor.

Additional Diagnostic Tools

Your veterinarian may also perform specialized procedures in order to remove a sample from the bone marrow, a kidney, or spleen. Additionally, the vet may drain an enlarged lymph node for further testing. Finally, it is possible that your vet may order for an abdominal ultrasound or/and an x-ray of the abdominal area and chest.

Grades of Dog Mast Cell Tumors

The tumor grade of the MCT refers to its level of malignancy. The grade will help your veterinarian make predictions as to how the tumor will develop and if it will affect other internal organs.

Grade I

Mast cell tumors that are classified as Grade I are typically benign and usually always occur on the surface of the skin. Just because they are benign doesn’t mean they should be ignored. Grade I MTCs can grow to be quite large and prove to be difficult to remove. However, the good news is that Grade I MTCs have not spread to the surrounding organs.

MCT Grade II

Mast cell tumors that are classified as Grade II are those that extend below the surface of the skin and into the subcutaneous tissues of the body. Treating Grade II MCTs can prove to be difficult to predict in terms of outcome. This is largely due to the unpredictable biological behavior of Grade II MCTs. An estimated 65% of Grade II mast cell tumors are cured with surgery. With that said, it is still possible for the tumor to return or for the spreading of cancer cells to occur.

Grade III

Grade III MCTs are those which prove to be the most difficult to treat. Mast cell tumors that are Grade III tend to spread quickly throughout the body. Even with aggressive treatment, the disease often has already developed deep below the skin’s surface. High-grade MCTs will often require surgery and cancer treatments including chemotherapy and radiation. Sadly, in most cases, Grade III mast cell tumors is not a disease that the dog can overcome.

Stages of Mast Cell Tumor Dog

The tumor stage of the MCT refers to its metastasis. The stage will help your vet determine to what degree the tumor has developed and spread. Different stages also refer to the degree to which the surrounding lymph nodes are affected.

MCT Stage I

Mast cell tumors that are classified as Stage I are those that involve only one tumor in the skin. They also do not have any lymph node involvement.

Stage II

Stage II MCTs are those that have caused secondary malignant growths. The MCTs originated as one tumor and then have spread to the surrounding lymph nodes.


Stage III mast cell tumors are characterized by either multiple tumors or by a large tumor that has spread into the subcutaneous tissues. Mast cell tumors that are Stage III may or may not have lymph node involvement.

Stage IV

Finally, Stage IV MCTs are characterized by one or more tumors with metastasis in the skin. It is also common for the tumors to have spread to other internal organs as well. Additionally, Stage IV mast cell tumors involve the lymph nodes.

Treatment for Mast Cell Tumor 

The grade and stage of the mast cell tumor will ultimately dictate the appropriate and necessary treatment.

As we previously mentioned, mast cell tumors have high levels of histamine. Therefore, any manipulation of the tumor may cause a sudden and extreme release of histamine to enter the bloodstream, causing a severe reaction. For this reason, your veterinarian may prescribe antihistamines to combat any adverse effect. An antihistamine medication will also help to protect the internal organs that could be harmed from the sudden histamine release.

Surgical Removal

Surgery to remove the tumor and surrounding lymph nodes is typically the preferred method of treatment when it comes to mast cell tumors in dogs. The Grade of the MTC will help your veterinarian predict the success rate of the surgery. A more aggressive surgery, as well as additional treatment such as chemotherapy, will often be necessary in cases where the cancer cells have spread to close to the surgical margins.

Radiation Therapy

In other cases, the tumors are not able to be surgically removed due to their location on the body. In these cases, your veterinary oncologist (a veterinarian who specializes in cancer patients) will likely recommend radiation therapy.

CBD for Dogs

By now, you’ve likely heard of the number of ways that CBD oil is proving to benefit our furry friends. From managing anxiety to reducing the severity and frequency of seizure, CBD oil is truly changing the game when it comes to the ways that we treat our dogs’ ailments. 

Due to the fact that the benefits of CBD are still a relatively new concept for many pet owners, there is still quite a bit of uncertainty and confusion surrounding the herb. For starters, many dog owners how it is possible to alleviate so many ailments with CBD. Let us explain. 

CBD is a powerful, all-natural anti-inflammatory. Why is this so important? Well, when experts trace the vast majority of ailments back to their source, they usually find that the health conditions all have one major thing in common: inflammation. Inflammation presents huge issues for people and animals alike. In fact, everything from allergies to cancer is linked to inflammation within the body. Therefore, supplementing your dog’s system with CBD is a way to safely relieve present inflammation and prevent future inflammation from developing. 

Treating Mast Cell Tumors with CBD

Now, we are certainly not negating the absolute importance of and the necessity for conventional medicine. Who knows where we would be without scientific advancements. However, what we are saying is that the power of all natural, holistic medicine should not be overlooked. In fact, every day, more and more research is continuing to emerge regarding the effectiveness of CBD for those suffering from cancer. Many experts state that their studies prove that CBD has an anti-tumor effect and can actually kill cancer cells. Of course, further research must be done before we can even begin to start substituting the herb for all conventional medicine. However, it is important for pet parents to know that CBD has proven time and time again to help dogs who are battling cancer. 

How CBD Supports Conventional Cancer Treatment

Furthermore, both chemotherapy and radiation therapy can cause Fido to experience adverse reactions. Gastrointestinal upset, including vomiting and diarrhea, as well as a total loss of appetite, are among the associated side effects. In these cases, CBD proves to be incredibly beneficial. If your dog is currently suffering from mast cell tumors, we highly recommend implementing CBD oil into their daily diet. 

Mast Cell Tumor Dog Life Expectancy

Survival times and overall prognosis for dogs diagnosed with mast cell tumours ultimately depends on several factors. First, prognosis depends greatly on the grade and stage of the MCTs. Survival times also depend on whether or not the dog receives the appropriate treatment. Surgeries and radiation treatment prove to be extremely pricey. Some pet owners will, unfortunately (and understandably), not be able to afford such treatment.

Sadly, dogs suffering from Stage III MCTs typically have a life expectancy of less than one year, even with aggressive treatment.

As you can see, while we urge pet owners to try to remain calm when it comes to new lumps and bumps you may find on your dog, it is imperative to not ignore them either. Your dog’s life may very well depend on whether or not they were diagnosed early on.

Mast Cell Tumor in Dogs: A Final Thought

Mast cell disease is a diagnosis that can devastate a dog owner. We understand the absolute heartache that a cancer diagnosis can cause and we are so sorry for our readers who are currently going through this. We want to encourage our readers to do their research when it comes to mast cell tumors and the available treatment options. Even something as simple as changing your dog’s diet to the highest quality possible can significantly help your dog through their recovery process. Additionally, implementing a supplement such as CBD oil can also prove to help the body function at its optimal level.

Due to the fact that the underlying cause of dog mast cell tumors remains unknown, prevention can prove to be nearly impossible. However, by making sure that you still aware of any changes you find in your dog is an effective way to catch any disease in its early stages. By being implicitly aware of your dog’s “normal” you can make sure you’re able to recognize when something is off and act accordingly.

From all of us here at Honest Paws, we sincerely hope your beloved four-legged friend feels better soon.


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About the author

Chelsea Hunt-Rivera

Chelsea Rivera is a Dedicated Pet Parent who loves to create amazing content for pet owners and is helping change pet wellness as the Head of Content for