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Mast Cell Tumors in Dogs

| Updated September 26, 2017

No pet owner wants to hear that their dog has been diagnosed with a tumor. Mast cell tumors, officially known as mastocytoma, are a type of tumor that typically requires significant veterinary treatment. If your dog has a mast cell tumor, you will need to educate yourself to understand your dog's treatment and help improve his prognosis.

Understanding Mast Cells

A mast cell tumor is a tumor that occurs when a number of mast cells form together. Mast cells are a part of your dog's immune system. They tend to exist primarily in the connective tissues, especially in areas close to the skin. Mast cells protect your dog against infections, repair damaged tissue and help form blood vessels. Mast cells contain a significant amount of histamine and heparin, which can help your dog's immune system combat allergic reactions. Mast cell tumors vary by their severity and are officially graded based on how likely your veterinarian believes it is that the tumor will be malignant. The factors that affect the grading are the size of the tumor, whether or not it has spread throughout your dog's lymph nodes and body as well as the specific biological makeup of the tumor.

Risk Factors

The specific cause of mast cell tumors has not been identified though several different factors are believed to play a part in their formation. Some breeds of dog are significantly more likely to develop mast cell tumors than others. Dogs that are prone to developing mast cell tumors are mostly members of brachycephalic breeds. Brachycephalic dog breeds have short, wide skulls and include boxers, pugs, English bulldogs and Boston terriers. Golden retrievers are also at high risk for developing mast cell tumors. The majority of dogs who develop mast cell tumors are also older; the average dog who develops this type of tumor tends to be around 8 years of age. Mast cell tumors can develop in younger dogs but it is less likely.

Recognizing a Mast Cell Tumor

Your veterinarian will have to make the official diagnosis of a mast cell tumor by performing a biopsy, but there are some tumor indicators that you may recognize as an owner. Mast cell tumors can be present on the skin or under the skin and may appear to change in size from day to day. They also may grow rapidly after having appeared relatively consistent for a long period of time. The tumor may appear reddened, itchy and can be mistaken for a bug bite, wart or other minor skin condition. Other medical symptoms, such as swollen lymph nodes, a loss of appetite, diarrhea and vomiting, may occur as the disease progresses.

Treating Mast Cell Tumors

If your vet suspects your dog has a mast cell tumor, he will aspirate it with a needle to check for unusually high numbers of mast cells and then biopsy it to confirm exact diagnosis . If he confirms that your dog has a malignant, or cancerous, mast cell tumor then he most likely will want to perform surgery to remove the tumor, possibly followed by chemotherapy and radiation. The prognosis for dogs with mast cell tumors varies greatly depending on how severe the original tumor was and whether or not the tumor had spread.