According to a recent study, mast cell tumors (MCT) account for 10.98% of skin tumors in dogs. Only lipomas (27.44%) and adenomas (14.08%), both of which are generally benign, were more frequently diagnosed.

Therefore, I think it’s safe to say that mast cell tumors are the most common type of oftentimes malignant skin cancer in dogs. Here is the information my practice provides to the owners of dogs that have been diagnosed with mast cell tumors.

What Are Mast Cell Tumors?

Mast cells are specialized cells within the body that respond to inflammation and allergies by releasing biological chemicals such as histamine, heparin, serotonin, and prostaglandins. Mast cell tumors are formed when there is an increased proliferation of these cells that is not controlled by normal mechanisms. These malignancies are capable of releasing an excessive amount of their biochemicals, which sometimes causes systemic problems including stomach ulcers, internal bleeding, and a variety of allergic manifestations.

Tumors arise primarily on the skin, but can be found within the oral cavity, larynx, trachea, chest, and gastrointestinal tract. Cancerous spread usually occurs within the lymph nodes, spleen, and liver.

How Are They Treated?

Treatment is dependent on the grade (degree of malignancy on biopsy) of the disease and the predicted aggressive behavior of the tumor. The higher the grade, the more aggressive and more advanced the cancer. Treatments include surgical excision of the tumor, radiation therapy, chemotherapies, and supportive care.

In some cases, anti-histamines and gastrointestinal protectants should be administered to combat the potential systemic effects of mast cell tumors.

What Symptoms Can Present as the Disease Progresses?

Early Stages

  • loss of appetite
  • weight loss
  • ulcerating mass
  • elayed wound healing
  • lethargy
  • licking the mass or lesion
  • vomiting/diarrhea

Late Stages

  • persistent early stages
  • abdominal pain
  • reclusive behavior, depression
  • vomiting blood
  • dark, tarry stools
  • exercise intolerance
  • difficulty breathing
  • coughing
  • bleeding disorders
  • enlarged lymph nodes
  • severe weight loss
  • unable to rise

Crisis — Immediate veterinary assistance needed regardless of the disease

  • difficulty breathing
  • prolonged seizures
  • uncontrollable vomiting/diarrhea
  • sudden collapse
  • profuse bleeding — internal or external
  • crying/whining from pain*

*It should be noted that most animals will instinctually hide their pain. Vocalization of any sort that is out of the ordinary for your pet may indicate that its pain and anxiety has become too much for it to bear. If your pet vocalizes due to pain or anxiety, please consult with your tending veterinarian immediately.

What Is the Prognosis?

Prognosis for MCT is directly related to the site of growth and tumor stage and grade. Complete removal of a grade 1 tumor usually results in an excellent prognosis. Dogs that are tumor-free after six months are considered unlikely to have a recurrence. Primary tumors that originate in areas other than the skin tend to be more aggressive. Mast cell tumors of the prepuce, groin, nail bed, and oral regions are generally the most malignant. Tumors of bone marrow or internal organs/tissue have a particularly grave prognosis.

Pets showing systemic signs and those whose tumors return after surgical removal also have a poor prognosis. Similarly, the faster the growth of the tumor, the more critical the case.

A personalized treatment plan is important to slow the progression of MCT. Talk to your veterinarian regarding the best treatment protocol for your pet.

© 2011 Home to Heaven, P.C. Content may not be reproduced without written consent from Home to Heaven, P.C.

Dr. Jennifer Coates

Image: Brian Goodman / via Shutterstock