Cutaneous mast cell tumors, or mast cell tumors that occur on the skin, make up about 20 percent of all dog skin tumors. While they can affect any breed, there are a few that are more prone to developing the tumors, such as boxers, golden retrievers, Boston terriers and pugs.
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Mast Cells
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According to Dr. Holly Nash of Doctors Foster and Smith, mast cell tumors form on mast cells—an essential part of the immune system. Mast cells help to attack foreign invaders such as parasites, by releasing heparin, histamines and enzymes that break down protein. Mast cells are normally found in the intestine and respiratory tract. A mast cell tumor is a tumor that is comprised of many mast cells clumped together.
Appearance
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Cutaneous mast cell tumors can vary greatly in their appearance. Although the tumors can surface anywhere on the dog’s body, they often appear in the genital, trunk and limb areas. The tumors can be small or large in appearance, as well as smooth, bumpy or ulcerated.
Causes
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Nash states that the exact cause of mast cell tumors is unknown; however, there is speculation about the reasons some dogs develop the tumors and others don’t. Genetics and viral sources are suspected causes, in addition to environmental factors. The Kate Connick’s Curious Canines website also states that mast cell tumors could develop because of chronic immune over-stimulation that occurs in dogs with allergies or other inflammatory conditions. Mast cell tumors typically occur in dogs that are between 8 and 9 years of age and dogs with short, wide heads.
Diagnosis
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A veterinarian can diagnose if a lump on a dog is in fact a mast cell tumor. The veterinarian can either insert a needle into the lump and collect cells to determine if the mass is a mast cell tumor, or he can surgically remove it and send it off for a biopsy. Surgery can be risky, however, because of the histamine and other elements in the tumors. If large amounts of the substances are released into the dog’s body upon removal, they can effect the animal’s heart rate, blood pressure and other body functions. In addition, the areas in which the tumors are removed often have difficulties healing.
Treatment
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Surgical removal is sometimes all that is necessary to eliminate the mast cell tumor from the dog. If the tumor is cancerous, however, additional treatment is required. If the tumor is not removable and is deemed malignant, radiation therapy is often indicated. Vets will also prescribe radiation to dogs that have had the cancerous tumors removed to reduce the chance of recurrence and to increase the dog’s survival rate. In addition, a vet may prescribe chemotherapy when the cancer has spread to multiple parts of the dog’s body.
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