Mast Cell Tumours

Overview:
Canine patients are commonly presented to veterinary clinics for evaluation of cutaneous and subcutaneous masses. One of the most common tumors with malignant potential that is diagnosed in this situation is the mast cell tumor. The importance of choosing an appropriate treatment strategy with these tumors is paramount; however, despite many studies dedicated to this topic, much is still not known.

Mast cells play several important roles in dogs and are integral to host defense mechanisms. Mast cell tumors are the most common canine cutaneous neoplasm, and several breeds including Boxers, bull terriers, and Labrador retrievers are noted to regularly develop mast cell tumors. When a mast cell tumor is suspected, the initial step in the diagnostic process is generally fine-needle aspiration. As mast cells exfoliate readily, diagnosis via cytology tends to be a relatively straightforward.

After a mast cell tumor has been confirmed, clinicians must decide what further diagnostics should be considered prior to primary tumor treatment. For mast cell tumors on the lower limb, fine-needle aspiration of the draining lymph node is highly recommended as this can affect surgical dose and post-operative adjuvant therapy recommendations. If a mast cell tumor is located on the pelvic limb proximal to the popliteal lymph node, the treating clinician should consider an abdominal ultrasound to evaluate the intra- abdominal lymph nodes. An abdominal ultrasound can also be recommended to assess other locations where mast cell tumors can be found, most commonly the liver and spleen.

The mainstay of treatment for mast cell tumors is surgical removal. With mast cell tumors, the palpable mass often does not provide a complete picture for the location of the tumor as these tumors tend to have “tentacles” of mast cells extending from the bulky tumor itself. These areas of mast cells should also be removed during recurrence at a future date.  [...]