Mast Cell Tumors in Dogs

by Sarah

Mast cells sound like something to do with ships, but they are just normal cells in the immune system that go around cleaning up foreign bodies and suspicious invaders. Mast cells are also called upon in the allergic reaction response.

Mast Cell Tumors in Dogs Symptoms

Mast cell is the most common form of canine cancer. When there is a DNA mutation of these cells, they can become cancerous; they divide and multiply and don’t follow the normal life cycle of healthy cells. Eventually, a tumor forms. For mast cell tumors, they are most commonly seen in the skin. These tumors can, however, be found in any part of the body – sometimes even in bone marrow, the spleen, and the liver but it is not as common for them to be found in internal organs. It is more likely for mast cell tumors to appear on the rear end, under the tail; on the legs; on the head; and on the neck.


Picture of Mast Cell tumor on a dog's leg

A whole variety of symptoms can be experienced by dogs who have mast cell tumors. To identify this type of tumor on a dog, it often presents as a red, raised bump that might look a bit raw or scabbed over. Sometimes they look like smooth bumps underneath the skin and some are significantly raised and stick out.

Most veterinarians agree that one of the main causes of mast cell tumors is genetics. Shar peis, Boxers, Rhodesian Ridgebacks, and Pugs are 4-8 times more likely to develop this type of cancer than other breeds. It is also believed that the formation of these tumors have something to do with the allergy process and possibly viruses (since mast cells are called upon when an immune system response is required).

Aside from seeing a tumor on the dog, there can also be a variety of symptoms which can make the diagnosis tough to nail down (if the tumor is internal). Loss of appetite, weight loss, vomiting, diarrhea can all be signs.

Types of Mast Cell Tumors in Dogs

Not all mast cell tumors behave the same. Some are more harmful than others. After the tumor is biopsied, it is given a grade of 1-3. Grade 1 is benign, Grade 2 is intermediate, and Grade 3 is malignant. It is important to note that even if the tumor is given a Grade of 1, it is always subject to change as cancer is unpredictable.

Mast cell cancer can also act like leukemia, with the cancerous mast cells found floating in the blood stream and in blood marrow. The lining of the intestines or stomach can also be another site of mast cell cancer.

Mast Cell Tumors Treatment & Survival Rates

Removal of the tumor(s) by surgery is the most common approach in treatment. Chemotherapy and radiation may also be recommended by the veterinarian. Prognosis of dogs with mast cell cancer depends on the tumor’s grade. Grade 1 tumors typically have an 83% survival rate; Grade 2 tumors typically have a 44% survival rate; Grade 3 tumors typically have a 6% survival rate. After surgery, tumors that are Grade 3 have a 50% chance of returning, while Grade 1 tumors have a very small chance of coming back.

Always seek the advice of your veterinarian whenever your dog has a medical issue.

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