Primer On Mast Cell Tumors In Dogs

Written and reviewed by John A. Bukowski, DVM, MPH, Ph.D.
and Susan E. Aiello, DVM, ELS 

Mast cells are inflammatory cells that originate in the bone marrow and circulate in many body tissues. They are important in allergic responses, tissue growth, wound healing, and nonallergic skin diseases.

Mast cell tumors are more common in dogs than in cats. 

They are most common in boxers, bull terriers, Boston terriers, Labrador retrievers, shar peis, golden retrievers, schnauzers and cocker spaniels. Although most mast cell tumors in dogs originate in the skin, they can be seen elsewhere, including the lungs, liver, and spleen.

Signs can be nonspecific and depend on the location of the tumor. These tumors are called the "great imitators" because they resemble many other tumor types.

In dogs, mast cell tumors commonly appear as red, itchy lumps. 

Their size may change rapidly, and they may disappear and return. The tumor produces inflammatory proteins that can cause inflammation at the tumor site and elsewhere in the body. Nonspecific signs include weight loss, vomiting, diarrhea, and lack of appetite.

Mast cell tumor. Image Wikipedia
Treatment largely depends on the stage of the tumor(s), which refers to determining the extent and severity of the disease. 

Taking a biopsy of the tumor is useful for staging, as is the number and location of tumors and the level of lymph node involvement. Many other factors are also considered in staging, including results of blood tests, x-rays and ultrasounds of the chest and abdomen, and analysis of bone marrow samples.

Surgery to remove the tumor from your dog is always the first and most important treatment. 

Further treatment, such as chemotherapy or radiation therapy, may be recommended depending on the staging.