Mast cell tumors arise most commonly in the skin. They develop from a normal component of body tissues called the mast cell that play a role in the process of tissue repair by releasing inflammatory mediators. Malignant mast cell tumors can spread to the lymph nodes, spleen, liver and bone marrow. Mast cell tumors are among the most common tumors of dogs, accounting for approximately 20 percent of all skin tumors. The cause of mast cell tumors is unknown.

Dogs that develop mast cell tumors often are older (usually 8 to 9 years of age), although they can occur in dogs of all ages. The most commonly affected breed are bulldogs but Labrador retrievers, Chinese shar peis and Bernese mountain dogs seem to have an increased risk.

Diagnosis and Treatment Notes:

  • Mast cell tumor is generally diagnosed by needle aspiration and microscopic examination of the cells. Biopsy of a mass is also diagnostic. Once diagnosed or suspected, dogs with mast cell tumor should have chest and abdominal x-rays and possibly abdominal ultrasound looking for spread of the tumor. Biopsy of regional lymph nodes and aspirate of the spleen would also be beneficial.
  • Treatment depends on the severity of the disease, your individual pet, and your veterinarian. Surgical removal of skin tumors is often curative if the surgical margins were wide and it hasn’t spread to other organs. If the mast cell tumor has spread, radiation and/or chemotherapy may be recommended. Discuss treatment details when your pet is diagnosed with this condition.


What to Watch for*:

  • Round, raised masses in the skin
  • Lack of appetite
  • Vomiting
  • Abdominal pain
  • Black tarry stools due to bleeding in the upper intestinal tract

Please notify us if you notice any of the above signs or if you have any questions!