Definition of Mast Cell Tumors
Mast cell tumors, also called mastocytomas, mast cell sarcomas or MCTs, are common cancerous accumulations of cells that form nodular skin masses. Normal mast cells are involved in inflammatory and allergic reactions. Why they aggregate into tumors in some dogs isn’t well-understood. The fact that certain breeds have a higher incidence of mast cell tumors suggests a genetic component. These tumors are most common in older dogs. About 50% of mast cell tumors are malignant, which means that they tend to progressively worsen and without treatment ultimately result in death. Mast cell tumors usually show up as isolated lumps on the skin, although they occasionally appear in cauliflower-like clusters. They often metastasize to the spleen, liver, bone marrow, lymph nodes and other skin sites. Most affected dogs show no symptoms of irritation or illness. Still, owners should have any lumps on their dog examined by a veterinarian.