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Featuring Demian Dressler, DVM and Sue Ettinger, DVM, Dip. ACVIM (Oncology), authors of The Dog Cancer Survival Guide

The Oncologist’s thoughts on mast cell tumors

Updated: November 22nd, 2018

If ever there was a tumor that fits the saying: “one size does NOT fit all”, it is mast cell tumors (MCT). These tumors are common, particularly skin tumors, in dogs. You may know a dog that had a mast cell tumor removed with surgery and went on to live many happy years to never hear from the MCT again. On the other end of the spectrum, you may know a dog with an aggressive MCT that recurred and/or metastasized quickly and lived just a few months.

What gives? Why is there so much variation in outcome? If your dog has a MCT, will it be a “good” MCT or a “bad” MCT? Can that be predicted? Why is there a new grading system? Do the new c-kit inhibitors (Palladia and Kinavet) work? In my next series of blogs, I hope to answer many questions about the complicated mast cell tumor.

First, let’s understand what MCT are. Normal mast cells are a type of immune system cell and play an important role in inflammation. While other immune system cells tend to circulate throughout the body, mast cells don’t – once they mature, they take up residence in specific tissues. While they can be found anywhere, many live in tissues that mark the boundary between the outside and internal environments; for example, the skin, the mouth, the digestive tract, the nasal passages, and the lungs.

Mast cells hold structures inside their cell walls called granules, which are like little sacks. The granules are filled with substances, or cytokines, including heparin and histamine, which help the immune system respond to problems. Heparin is a blood thinner which helps defend the body against foreign invaders, and histamine is a chemical that triggers inflammation. Normal mast cells release these substances when prompted by the immune system. In addition to their role in inflammation, mast cells are involved in allergies, anaphylaxis (systemic inflammation), the healing of wounds, and defense against outside pathogens.

In this seminar, Dr. Dressler addresses a number of important topics on Mast Cell Tumors, so be sure to get your copy for more information!

Mast cell tumors are cancerous accumulations of mast cells with a malignant potential. MCT is very rarely found in humans, but it is the most common malignant skin tumor in dogs, accounting for 15-20% of all skin tumors. Mast cell tumors first occur in the skin and the subcutaneous tissues beneath the skin. It’s very rare to find MCT in internal organs without a primary skin tumor, but skin tumors can spread to the regional lymph nodes, the spleen, the liver, other places deep in the abdomen, and to the bone marrow.

What causes MCT? Like most tumors, the exact cause is not known. About one-third of dogs have a genetic mutation in a protein called the c-kit oncogene. Unlike skin cancer in humans, which is often associated with sun exposure, studies have found no link between sun exposure and MCT in dogs. But chronic inflammation of the skin may predispose dogs to develop MCT, as can the repeated application of skin irritants.

We also tend to see it more commonly in the following breeds: Boxers, Boston Terriers, Labradors, Golden Retrievers, Pugs, and Staffordshire Bull Terriers. Boxers tend to develop low and intermediate grade tumors.

MCT are one of the most common tumors I see in my oncology practice at the Animal Specialty Center. When should you see an oncologist for MCT? We will pick up there at my next post. In the meantime, remember there is a lot more information about MCT in the Guide.

Get the book to read more on Mast Cell Tumors from an Oncologists Perspective!

Leave a Comment

  1. Charbel on November 10, 2022 at 12:10 am


    I understand that chronic skin inflammation causes mast cancer. My question is: what causes chronic skin inflammation? Can dog who get bite from another dog cause chronic skin inflammation?

    • Molly Jacobson on November 16, 2022 at 3:33 pm

      Chronic skin inflammation could come from an injury or a bug bite that has a hard time healing. It could also be mites or allergies, for example. There are many things that can cause long term, low grade, chronic inflammation.

  2. Dee on June 20, 2020 at 9:00 am

    When to know when it’s time to let mast cell tumors go untreated? How many surgeries is it actually ethical to put these dogs through? We have a 8.5 year old Rhodesian Ridgeback mix who had had his first MCT surgically removed at age 6. He had another removed 18 months later (New location) along with a large, quickly growing lipoma. Both MCTs removed were stage 2. Now he has another lump that I am pretty sure is another MCT in another location. We had it aspirated early on but results came back negative, though another vet told us it may have just been too early to see the cells. I am at a loss as to what to do with my dear friend. He has other large slow growing lipomas. My vet feels fine with surgery and sees no problem continuing to do it indefinitely as long as it is needed, nonchalantly saying he’s “just a lumpy dog.” I don’t know!!!

  3. Jane Webster on October 27, 2019 at 1:50 pm

    My 10yr old cairn terrier has developed a mast tumour near her front leg and chest . She is having it surgically removed .She is on oral benadryl.I will
    need more information to aid in her recovery.
    J.Webster ,Perth Ontario,Canada


    • Dog Cancer Vet Team on October 28, 2019 at 8:21 am

      Hello Jane,

      Thanks for writing. We have a number of MCT articles on the Dog Cancer Blog that you may find helpful. Here’s the link:

      Dr. Sue also wrote an entire chapter on MCT in the Dog Cancer Survival Guide where she discusses diagnosis, prognosis, grade, protocols and much more, that you may also find beneficial 🙂

    • Jayne Whittle on October 29, 2019 at 3:32 am

      Jane…invest in the book by Dr Demian Dressler and Dr Sue Ettinger…A survival guide to canine cancer I believe…investigate Apocaps whom Dr Dressler developed, also I’m Yunity(Penn State did a small study on this supplement), as well there is another supplement Dr Dressler developed…and Yunnan Bayiou…also a lot of folks in Canada are using Essiac Tea capsules…I wish I had made it to Dr Sue Ettinger…if it were me…Dr Sue is only as far asa Norwalk CT…I’d make the trip…as well I met a man in Bangor ME…his dog had anal gland cancer and had some surgery but it did not get it all…put on palladia…they gave the dog 4 months but if he lived longer they wanted him to stay on palladia for 9…the canine could only do 5 months…that was 3 yrs ago, Jayne Nova Scotia Canada

    • Yamila on March 3, 2020 at 6:25 am

      Hi Jane, I know this comment was posted a while back but I am very interested in finding out how you cared for your dog post-surgery and if there are any tips you could possibly give me to make it easier on my puppy. He’s only 2 and he’s in the OR at this moment removing two MCT’s. Any extra information is helpful. Thank you.

  4. Natalie Forowa on October 23, 2019 at 8:39 am

    How does exercise affect mast cell tumor in a dog?

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