Mast Cell Tumors in Dogs - The Trupanion Blog
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Mast Cell Tumors in Dogs

Pitbulls are prone to mast cell tumors in dogs
Skin tumors and tumors that are just right under the skin (subcutaneous tumors) are the most common tumors found in dogs. Approximately 80% of all skin tumors are benign but quickly diagnosing a malignant skin tumor is critical to improving your dog’s prognosis. Learn more about what you need to know about mast cell tumors in dogs.

Mast cell tumors in dogs: what you need to know 

In veterinary medicine, one of the most dangerous things you can say is, “let’s wait and see.” This is especially true when it comes to tumors, lumps, and bumps. Good, aggressive, thorough veterinary care more often will involve some form of biopsy when a new lump is discovered on your dog. This is particularly important if:

  • Your dog is older (more than 6 or 7 years old)
  • The lump grows quickly
  • Your dog has had a malignant tumor before
  • Your dog is a purebred (and especially a Boxer, Rhodesian Ridgeback, Pug, Boston Terrier, Pitbull, Weimaraner, Shar-Pei, Bulldog)

How Common are Mast Cell Tumors in Dogs?

Skin and subcutaneous tumors account for approximately 1/3 of all dog cancers. mast cell tumors are the most common malignancy of the skin in dogs and the breeds listed above are at least 5 times more likely to develop a mast cell tumor than the general dog population.

The good news is, they are most often “solitary”—a single tumor—and upwards of 50% of all mast cell tumors will only cause troubles locally and will not spread.

What are the Symptoms of a Mast Cell Tumor in Dogs?

Mast cell tumors have long been known as “the great pretender” – they can look and feel like anything! This makes it particularly important to have a biopsy performed when a new lump or bump pops up on your dog. A mast cell tumor may have the following symptoms:

  • A raised bump in any location on the body.
  • Slow or rapid growth.
  • Hair remains on-top of growth or the lump is hairless and ulcerated
  • Systemic signs like vomiting, diarrhea, or loss of appetite

Lumps that pop up in the groin, by the rectum, mouth, feet or eyelids are more likely to be aggressive. If your dog is systemically ill (not eating, vomiting, diarrhea), the mast cell tumor may also be aggressive and potentially more difficult to treat.

Making a diagnosis

Unlike some cancers where a diagnosis can be difficult, a simple fine needle biopsy can often lead to the diagnosis of mast cell tumor.  From there, however, determining the grade or stage of this worrisome tumor becomes more complicated. Your veterinarian will discuss surgery to remove the tumor and then a histopathological assessment including special staining and sometimes special blood tests. There have been dramatic improvements in how we classify mast cell tumors. These dramatic improvements are allowing veterinary surgeons and oncologists to provide very specific advice for your dog when a mast cell tumor is diagnosed.

Treatment for Mast Cell Tumors in Dogs

Treatment varies depending on the location of the tumor. Surgery is often performed and then based upon additional testing, additional therapies might be indicated. Additional therapy to help prevent recurrence can be critical to extending your dog’s high-quality life when a high grade or malignant mast cell tumor is diagnosed.

What is a Typical Prognosis for Mast Cell Tumors in Dogs?

Prognosis varies with mast cell tumors but remember that more than 50% of mast cell tumors stay local and do not spread. Removing an ear (the flap part or pinnae) as an example might seem extreme but it can cure your dog. The advances in describing or classifying mast cell tumors and the corresponding treatments that are available are truly amazing. Talk to your family veterinarian about your closest veterinary oncologist. It is very impressive how modern veterinary medicine can really help our dogs when a diagnosis like a mast cell tumor or mast cell disease is made.


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