Mast cell tumors are commonly diagnosed in dogs and account for approximately 20% (one in five) of all skin tumors seen on dogs.
Some breeds of dogs are more likely than others to develop mast cell tumors. Dog breeds most commonly affected include:
- Boxers
- English Bulldogs
- Boston Terriers
- Shar Peis
- Labrador Retrievers
- Golden Retrievers
- Schnauzers
- Cocker Spaniels
What does a Mast Cell Tumor Look Like?
Mast cell tumors can vary in appearance. Most often there will be a mass or growth present on or under the skin. The area surrounding the mass may be swollen and it is possible to see rapid changes in the size of the mass.
Dogs affected with mast cell tumors may have only one tumor or may have several tumors present.
Mast cell tumors can also be itchy and uncomfortable for the affected dog.
How are Mast Cell Tumors in Dogs Diagnosed?
Mast cell tumors in dogs can be diagnosed by a fine needle aspirate, which involves collecting cells from the mass with the aid of a needle and examining the cells under a microscope. However, to determine the prognosis associated with a mast cell tumor in a dog, a tissue biopsy must be performed.
Mast cell tumors in dogs are graded from one to three, with a grade of one being less invasive and having a better prognosis than other grades. Grade three mast cell tumors tend to be the most invasive with the potential to spread to other parts of the body and are much more difficult to treat.
Mast cell tumors in dogs are also staged from one to four, depending on whether there are one or more lesions present, whether the lesions have spread to the lymph nodes and whether the affected dog is clinically ill or not.
How are Mast Cell Tumors in Dogs Treated?
Treatment for mast cell tumors in dogs may involve:
- surgical removal of tumors
- radiation therapy
- chemotherapy
Surgery as a Treatment for Mast Cell Tumors in Dogs
Surgery to remove the mast cell tumor is sometimes curative in itself if the mast cell tumor is not extremely invasive and surgery is effective in removing the entire lesion. However, mast cell tumors are very frequently quite invasive and removal of the entire mast cell tumor is often not possible or practical.
Surgical removal of the mast cell tumor will allow proper staging of the tumor to determine what additional treatment needs to be performed to treat this canine skin cancer.
When evaluating the tissue sample obtained from surgical removal of the mast cell tumor, the diagnosis of mast cell tumor will be confirmed, the mast cell tumor will be staged and the width of the tissue margins which are free of tumor will be measured.
Staging and the width of the tissue margins which are free of tumor cells together with the location of the mass, the health of the dog and the grade of the mast cell tumor will determine whether further treatment with radiation therapy or chemotherapy is needed.
Radiation Therapy as Treatment for Mast Cell Tumors in Dogs
Radiation therapy offers the chance of a cure for mast cell tumors which are less invasive. However, radiation therapy is expensive and there may not be a facility able to offer this option within a convenient distance in many locations.
Chemotherapy as Treatment for Mast Cell Tumors in Dogs
Corticosteroids such as prednisone are the most commonly used chemotherapeutic agent for mast cell tumors in dogs. Other drugs which may be used are vinblastine and lomustine.
Though not truly thought of as chemotherapeutic agents, antihistamine medications such as Benadryl and Pepcid AC may help ease some of the commonly seen symptoms of dogs suffering from mast cell tumors and these medications are commonly used to help treat mast cell tumors.
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