Mast Cells are normally found throughout the body. They release active chemicals, such as histamine, heparin, serotonin, prostaglandins, and proteolytic enzymes. These chemicals are vital to body function, especially to help the immune system, but when the cells turn cancerous they can be produced to excess which can be extremely damaging.
Mast cell tumours are also known by other names such as hystiocytic mastocytoma; mast cell sarcoma, and mastocytosis. These tumours are the most common skin tumours found in dogs. The most common location is the skin, followed by the spleen, liver, and then the bone marrow.
The tumours can vary widely in shape, texture, size, appearance, and location, and cannot be clearly identified without biopsy and pathology. They behave in a completely unpredictable manner. Their behaviour is best predicted by the pathologist’s grade, but depending on the grade of tumour, there can be good survival rates
Prednisolone is commonly used to reduce swelling before, or instead of, removal of the tumour. It is fairly cheap treatment, but does have side effects such as excessive drinking, urination, appetite, and potential stomach upset. Sometimes other chemotherapy drugs are used, including cyclophosphamide, vinblastine, vincristine, and doxorubicin. Newer targeted drugs such as masitinib and toceranib are now also available.
Dogs that have had mast cell tumours are more likely to develop more. Statistics suggest that half of all these tumours are curable.
**Accuracy checked 12 September 2013,
Dr Ken Wyatt BSc BVMS FANZCVS,
Registered Specialist in Veterinary Oncology,
Perth Veterinary Oncology
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