MAST CELL TUMORS AND THEIR TREATMENT
Mast cell tumors are a common tumor type for dogs, especially in Pit Bulls, Retriever, and Shepherd breeds. They are less common in cats.
Mast cells are one of the cell types involved in the immune system, in particular the mediation of allergies and sensitivities. Thus it makes sense that the breeds mentioned above are the most commonly affected, since they are breeds which are known for their allergic problems.
In general, early mast cell tumors appear as simple thickening of the skin, rather than as more prominent “lumps” like lipomas create. This makes their early diagnosis very difficult.
Once we find a suspicious bump, the best way to make a diagnosis is to do a “fine needle aspirate”, where we stick a small needle into the mass and aspirate, or suck back, some of the cells within the bump. We then look at those cells under the microscope, and mast cells have a very characteristic appearance. If there is any question, we always recommend sending the microscope slide off for histopathologic exam by a pathology specialist.
Once diagnosed, the primary form of treatment for mast cell tumors is their surgical removal. Because they have a tendency to develop roots, we always try to get a margin of at least one centimeter—and preferably two—both around and under the mass.
The early excision of these masses is very important when you realize that they have a tendency to metastasize, or spread to distant sites, via the bloodstream. Thus the bumps you and we feel on the skin may not be the only ones your pet has, and the longer they are in place before surgical removal the higher the likelihood of internal spread becomes. Regional lymph nodes and the spleen are common sites of metastasis.
It is important that you understand that once a pet begins developing mast cell tumors, it is very likely that you will see others develop in the future. For this reason, we recommend weekly “massages” of your pet in an effort to detect other tumors as early as possible.
Once excised, we always recommend the histopathologic exam of your pet’s tumor for staging purposes. Mast cell tumors are typically graded on the Patnaik scale from 1- 3. The lower the number, the less aggressive such masses are. The higher the grade, the more likely we are to see recurrence and/or metastasis.
Because mast cells are a normal constituent of allergic responses, as mast cell tumors develop we may see signs of allergies develop—itchy skin or GI symptoms like vomiting or diarrhea. For this reason, it is never a bad idea to begin a mast cell tumor patient on simple antihistamines like Benadryl (dosed at 2 mg per lb body weight 2x a day) or Zyrtec (1 mg per lb body weight once a day), and Pepsid AC (1 mg per lb body weight once daily) to protect the stomach.
Along with surgery, there are four other forms of treatment for mast cell tumors.
First, from an integrative approach, our goal is to mellow the immune system. We do this by trying to avoid allergies, minimize inflammatory disease like dental problems or arthritis, and by minimizing vaccines.
Secondly, we can use natural supplements to help reduce inflammation throughout the body. These include…..
-omega 3 fatty acids in fish oil (50 mg per lb body weight per day)
-curcumin (the dosage depends upon the purity of your product—we carry Transcend, the most
bioavailable form of curcumin on the market)
-Undenatured type 2 collagen to reduce arthritic inflammation
-mushroom therapy to reduce systemic inflammation (shitake and maitake D fraction)
-decaffeinated green tea at a dose of 20 mg per lb body weight with food
For masses that are too large to be removed or that are surgically inaccessible, there is an oral form of chemotherapy called Palladia. While expensive, it has been proven to reduce both the rate of growth and the metastasis of mast cell tumors, and is very well tolerated by most patients.
Perhaps the most exciting development is that we in veterinary medicine now have access to the same immunotherapy used in advanced human cancer treatment. Basically this involves a) the surgical removal of at least part of the tumor, b) sending it off to a specialized lab, where they will c) develop an injectable vaccine SPECIFICALLY against your dog’s tumor. This enables us to use your dog’s own immune system to fight their cancer.
And the most important part of all? At Mission Animal Hospital, we’ll help you however we can.