Mast Cell Tumor:  Histiocytic Mastocytoma, Mast Cell Sarcoma

Affected Animals:  Mast cell tumors are very common in dogs. Dog breeds more commonly affected include boxers, Boston terriers, bullmastiffs, English setters, and golden retrievers. Older dogs are more commonly affected, but MCT can occur in any age or sex.

Information and Overview:   Mast cell tumors, or MCTs, are among the most common tumors in dogs, with the skin being the most common primary site for MCTs in this species. Mast cell tumors can occur anywhere in the body. The systemic form of mast cell tumors, with visceral, lymphatic or bone marrow involvement is referred to as mastocytosis. Despite the sometimes "benign" appearance, mast cell tumors tend to exhibit a very unpredictable biological behavior. Therefore many veterinary oncologists consider all mast cell tumors malignant until proven otherwise. The mean age of dogs with mast cell tumors is nine years. Predisposition to mast cell tumors appears to occur in Boxers, Boston terriers, beagles, bulldogs, and Schnauzers. Although Boxers appear to be at a higher risk for development of MCTs, most tumors in this breed tend to be well differentiated. When feasible, treatment involves addressing the tumor locally, with surgery and/or radiation treatment. In some cases, systemic treatment may be necessary, but is often not successful due to the extent of the disease.

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