Jun 07 2016

Mast Cell Tumors |Winslow Animal Hospital Dog & Cat

Mast Cells

Mast cells are a special type of cell that are distributed throughout the body and help animals respond to inflammation and allergies. When stimulated, these cells can release active chemicals into the body, such as histamine, heparin, seratonin, prostaglandins, and proteolytic enzymes. Each of these chemicals are an important part of healthy function of the body, especially in the immune system response. When these chemicals are released in chronic excess, however, they can be damaging.
Mast cell tumors are cancerous growths of mast cells. The main threat from these tumors is secondary damage caused by the release of chemicals that they produce. Symptoms can  include gastric ulcers, internal bleeding, and a range of allergic responses. As a result, mast cell tumors lessen quality of life as well as the lifespan of the animal. Mast cell tumors vary in size, shape, appearance, texture, and location. Some tumors are relatively innocent, while others are aggressively malignant.  To be certain there is a mast cell tumor present, a biopsy must be performed.
Mast cell tumors are some of the most common tumors in dogs. Approximately 1/3 of all tumors in dogs are skin tumors, and up to 20% of those are mast cell tumors. Mast cell tumors usually occur in the skin, but are also found in the spleen, liver, bone marrow, and other parts of the body.  Just over 1 in 10 mast cell tumors occur in more than one location.

Risk Factors for Mast Cell Tumors

Mast cell tumors occur commonly in dogs, less frequently in cats, and very rarely in human beings. They occur in dogs of all ages, breeds, and genders, anywhere in the body. Some breeds are predisposed to developing mast cell tumors, such as Beagles, Boston Terriers, Boxers, Bulldogs, Bullmastifs, Bull Terriers, Dachshunds, English Setters, Fox Terriers, Golden Retrievers, Labrador Retrievers, Schnauzers, American Staffordshire Terriers, and Weimaraners. Boxers are at the highest risk, though the tumors are often not as aggressive in this breed. Mast cell tumors may be associated with chronic immune over-stimulation that occurs in dogs with allergies or other inflammatory conditions. Older dogs are more likely to develop cancerous growths, with the average age of a dog with a mast cell tumor being 8-9 years old.


Symptoms can vary, depending on the location of the tumor and its degree of development. Signs may include:

  • tumor
  • loss of appetite
  • vomiting
  • bloody vomit
  • diarrhea
  • abdominal pain
  • dark feces
  • itchiness
  • lethargy
  • anorexia
  • irregular hearth rhythm/blood pressure
  • coughing
  • labored breathing
  • delayed wound healing
  • bleeding disorders
  • enlarged lymph nodes

Treating Mast Cell Tumors

The first step in treating a mast cell tumor is finding it. Hopefully the process can begin early when a Pet-Parent notices a growth on their dog. The veterinarian may use a fine needle to remove a sample for a preliminary biopsy prior to tumor removal.  Blood tests may include a Complete Blood Count (CBC) and a serum chemistry profile. The CBC may show low or high white blood cell count, low platelet count, and elevated mast cell counts. Other tests may include urinalysis, x-rays, ultrasound, and aspirates of the lymph nodes or bone marrow.

The tumor is almost always surgically removed, if possible. The veterinarian performing the surgery removes a margin of healthy tissue around the tumor to capture any stray cancerous cells that may not be immediately  obvious. After the tumor is removed, it is submitted for biopsy in a laboratory. One of the important aspects of the biopsy is determining whether or not the margins contain invasive cancerous cells.

The pathologist assigns a “grade” to the tumor, an assessment of how well differentiated the cells are and, by extension, how aggressively malignant the cancer appears to be. High-grade tumors may be treated with chemotherapy.

Mast Cell Tumor small

Dr. Coudrai recently removed this mass from a dog. Biopsy results will soon tell us for sure if it is a Mast Cell Tumor.

LifeLearn Admin | Pet Health, Pet Stories, Surgery, What's New at Winslow Animal Hospital!

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