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What are Mast Cell Tumors?

Brachycephalic breeds, as well as retriever breeds, are more likely to develop mast cell tumors, especially Pugs, Boxers, Bulldogs and Boston Terriers. Any breed, though, can develop mast cell tumors. 

MCT varies in appearance and it can be difficult to diagnose based solely on appearance. Mast cell tumors can present as raised lumps or bumps or they can be found just under the skin. These tumors contain granules that are filled with substances that can be released into your dog’s bloodstream. This can cause potentially life threatening complications.

Mast cell tumors or MCT in dogs are a type of cancer that affects the body’s normal response to allergens and inflammation. MCT is also called mastocytoma. Mast cell tumors in dogs usually present as skin tumors but they can affect other areas of the body, including the liver, spleen, gastrointestinal tract and bone marrow.

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Symptoms of Mast Cell Tumors in Dogs

The symptoms of mast cell tumors in dogs will be dependent on the grade and location of the tumor as well as the stage of the cancer. If you notice any mass or tumor on your dog’s skin, you should have it checked out by your veterinarian.

  • Tumor on the skin or under the skin
  • Tumor that fluctuates in size
  • Rapid growth of a tumor
  • Redness or fluid buildup on or around the tumo
  • Resembles a wart, insect bite or allergic reaction
  • Enlarged lymph nodes
  • Vomiting
  • Loss of appetite
  • Diarrhea


Stages of Mast Cell Tumors include:

  • Stage 1: Single skin tumor without metastasi
  • Stage 2: Single skin tumor with metastasis into the lymph nodes
  • Stage 3: Multiple skin tumors or one large tumor subcutaneously
  • Stage 4: Tumor with metastasis to organs or in the blood

Causes of Mast Cell Tumors in Dogs

The actual cause of mast cell tumors in dogs is unknown. Researchers have theories that have not been yet been proven. Like many of the cancers that are presenting in dogs, MCT could be caused by environmental factors. It may also be caused by diet or lack of certain nutrients. MCT may also be genetic; however, this is a less likely cause. Researchers have not found a solid link between genetics and mast cell tumors.

Diagnosis of Mast Cell Tumors in Dogs

When you see your veterinarian, they will ask you for your dog’s medical history as well as any changes in behavior. A physical examination will be performed and your veterinarian will closely look at any masses or tumors present on the skin or subcutaneously. A biopsy will probably be performed. This generally requires that a needle be inserted into the mass and drawing out any fluid or cells. If the mass is hard and unable to be aspirated using a needle then a surgical biopsy may be necessary. The lymph nodes may also be needle aspirated for a biopsy. 

An abdominal ultrasound may also be done to determine if the cancer has spread to the organs. A bone marrow aspiration may also be needed to determine whether or not the cancer has spread into the bone marrow. Other diagnostic tests that may be performed to determine the overall health of your dog include a complete blood count, biochemistry panel and urinalysis.

Treatment of Mast Cell Tumors in Dogs

Once mast cell tumors have been diagnosed in your dog, your veterinarian will discuss treatment options with you. Treatments will vary depending on the location, size and stage of the tumors. The tumors will be removed surgically if possible and chemotherapy is generally recommended. Radiation therapy is also recommended to ensure that all of the cancer cells have been eradicated. 

While under treatments, your dog may also be given additional medications as supportive care to make their quality of life better. Steroids, usually prednisone, are given since they have been proven to kill cancerous mast cells. Antihistamines and antacids are given to help alleviate the side effects of chemotherapy and steroids.

Recovery of Mast Cell Tumors in Dogs

Once your veterinarian makes their diagnosis and begins treatments they will be able to give you a better understanding of your dog’s prognosis. Prognosis will vary depending on several factors including tumor stage and grade as well as if the tumors can be completely surgically removed. If your dog has a recurrent mast cell tumor, their prognosis will not be as good as if this were their first diagnosis.

Dogs that are diagnosed in later stages where the cancer has spread to other organs will have a poor prognosis. The main focus of treatments for these dogs is to maintain a comfortable quality of life for as long as possible.

Mast Cell Tumors Questions and Advice from Veterinary Professionals

Basenji mix
11 Years
Moderate condition
0 found helpful
Moderate condition

Has Symptoms

Subcutaneous Mast Cell Tumor

Medication Used


My basenji 11 year old dog had surgery last week and had a tumor removed from her upper hind quarters. I just received a call from the vet and the biopsy results came back as a subcutaneous mast cell tumor with a mitotic figure of 16.

About 3 1/2 years ago she had her first tumor removed and it was a mast cell tumor, state 2 with zero mitotic figures. She had several surgeries since then and until about 4 months ago all biopsies came back begin.

About 4 months ago she had 4 lumps removed and 1 was a mast cell tumor, state 2 with zero mitotic figures.

I am scheduling an appointment with a "doggie" oncologist to see what the best course of action is to ensure Lilie has a good quality of life.

I have my follow up appointment with the vet for removal of stitches next week. Are there any questions or things that you can think of that I need to ask the oncologist when I have the appointment.

Thank you for your time.

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Pit Lab
8 Years
Critical condition
0 found helpful
Critical condition

Has Symptoms

growth under skin

Medication Used


Ziggy had a growth on his skin and it was surgically removed. About 2 months later, I noticed a lump under his skin. I called the vet and the appointment was 2 days later. In that time, the tumor tripled in size. After 2 hours of surgery, the growth was was removed. Before the biopsy came back there was another lump. We started chemo and the new tumor is no longer detectable with palpitations. Yahoooo!! Ziggy is back to normal and thriving! We will continue chemo for 8 weeks.

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Labrador Retriever
10 Years
Mild condition
0 found helpful
Mild condition

Has Symptoms

Mast cell tumor

My dog has been diagnosed with a Mast Cell Tumor by its ear. The surgeon is recommending a surgical removal and sending the mass for checking the stage.

He also has Hypercalcemia and the surgeon wants to operate on that at the same time as the Mast.

The Cost of these proceedures is coming out to be very high ($6000 for the surgery, not including the test for Cancer). Several doctors have already looked at the Dog - Oncologist, Internal Medicine Doctor and Surgeon and it has cost me $2200 upto this point.

I want to find out after spending close to $10,000 how long will my dog live (he is 9 1/2) and what will be his quality of life.

The dog is otherwise healthy.

Dr. Callum Turner, DVM
Dr. Callum Turner, DVM
3320 Recommendations
There are many factors to consider when evaluating prognosis and lifespan, it is difficult to give a specific answer without knowing more information especially regarding the cause of the hypercalcemia; is the hypercalcemia due to an enlarged parathyroid gland? A tumour of the parathyroid gland? Or other issues. I feel that your Veterinarian, Oncologist, Internal Medicine Specialist and Surgeon have all examined Max and didn’t give you an answer. Regards Dr Callum Turner DVM

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