What Are Mast Cell Tumors?


A Note From Dr. Chris:

Mast cell tumors are the most frequently encountered skin tumor found in dogs and the second most commonly seen skin tumor in cats.  The mast cell tumor arises from dermal tissue mast cells and is considered malignant.  Although it is most frequently seen in older pets, I have personally seen this type of tumor in much younger pets as well.  Siamese cats seem to be predisposed, as well as several breeds of dogs.  The breeds that seem to present with mast cell tumors more frequently include Boxers, Pugs, Boston terriers, Labradors, Beagles, Golden Retrievers, and Weimaraners.


This tumor can take on various appearances.  You may notice a raised red nodule that looks more like a bite or sting.  Other times you may find large ulcerated areas on your pet’s skin.  These types of tumors vary in size as well; they can be very small or include a large area of skin.  

Luckily, mast cell tumors can respond very well to treatment if found early on in the disease process.  If you notice a lump of bump on your pet, go ahead and make an appointment to see your veterinarian.  While at the vet’s office, have them do a quick fine needle aspirate.  This is a very simple diagnostic test that allows your veterinarian to evaluate the general cell type found in the mass.  A clinical pathologist will then read and interpret the results of the aspirate.  These tests allow for a quick diagnosis, which will allow your veterinarian to go ahead and schedule the surgical removal of the mast cell tumor. Usually, surgery is an effective treatment if a mast cell tumor can be removed and good margins visualized.

I always suggest removal of lumps or bumps that cannot be readily diagnosed by a visual evaluation.  Don’t just simply watch a skin tumor until it starts changing in appearance.  It is always best to be cautious and get it checked out by your veterinarian.  I believe the old surgical saying is “if in doubt, cut it out.” 

Our information is not intended to replace the advice of your veterinarian.  Do not use this information for diagnostic purposes. Always take your pet to your veterinarian to obtain a diagnosis and course of treatment.