Mast Cell Tumors in Dogs: An Overview

Dog Breeds

Canine mast cell tumors, also known as mastocytomas, mast cell sarcomas or MCTs, are abnormal, cancerous (neoplastic) and unfortunately fairly common accumulations of mast cells that form nodular skin masses in dogs. About fifty percent of canine mast cell tumors are malignant.

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Definition of Mast Cell Tumors

Canine mast cell tumors, also known as mastocytomas, mast cell sarcomas or MCTs, are abnormal, cancerous (neoplastic) and unfortunately fairly common accumulations of mast cells that form nodular skin masses in dogs. About fifty percent of canine mast cell tumors are malignant. When MCTs metastasize, they typically go first to lymph nodes in the region of the primary mass. Thereafter, metastasis normally is to the spleen, liver, mesenteric lymph nodes, other cutaneous (skin) sites and to the bone marrow. MCTs are one of the most frequently diagnosed cancers in domestic dogs.

Causes of Canine Mast Cell Tumors

Mast cells normally are involved in inflammatory and allergic responses as part of the body’s appropriate response to contact with allergens or other offending substances. Mast cells contain granules of various bioactive substances called cytokines, including histamine and heparin. When the cells degenerate or break apart (degranulate), those granules are released into circulation, causing a number of different bodily effects that can contribute to gastrointestinal ulceration, skin lesions, itchiness, bleeding disorders and systemic symptoms. Why mast cells accumulate into potentially malignant tumors in dogs is not known. The fact that certain breeds have a higher incidence of this type of cancer suggests a likely but complex genetic component.

Prevention of Canine Mast Cell Tumors

Because the causes of mast cell tumors are not known or even well-understood, there is no real way to prevent their development in domestic dogs. However, because more than 15% of dogs diagnosed with a mast cell tumor will develop more of them during their lifetime, affected animals should be rechecked by a veterinarian regularly, so that any new growths can be identified and treated as quickly as possible.

Special Note obn Mast Cell Tumor

The outlook for mast cell tumors depends on how progressed the cancer is. Mast cell tumors graded in the I – II stage usually have a good prognosis, while mast cell tumors in the III – IV stage have a guarded prognosis and are dependent on the response to chemotherapy and radiation treatments.

Symptoms and Types