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Featuring Demian Dressler, DVM and Sue Ettinger, DVM, Dip. ACVIM (Oncology), authors of The Dog Cancer Survival Guide

Testing for Mast Cell Tumor Spread: Buffy Coat?

Updated: October 1st, 2018

Mast cell tumors occur commonly in the dog.

There are three basic grades of mast cell tumor (Grade 1, 2 and 3).  The Grade of the mast cell tumor is useful because it gives the veterinarian or oncologist an idea of how aggressive the mast cell tumor will be.

Another way of talking about this is how “malignant” the mast cell tumor is expected to behave.  The more malignant, the higher the odds of spread to distant sites, and the more difficult the treatment.

If a mast cell tumor is an aggressive grade 2 or a grade 3, often staging will be performed.  Staging is the process where the doctor looks for evidence to suggest tumor spread into distant sites.

A particular test was used, and sometimes is still used, to see if there is mast cell tumor spread.  This test is called a buffy coat smear, or buffy coat analysis.

A buffy coat analysis is performed by placing a small amount of blood in a very thin tube called a microhematocrit tube.  The tube end is plugged and the tube is spun at high speeds in a centrifuge.

The high speed causes cells that are more dense to settle towards the bottom of the tube, while those that are less dense remain higher in the tube.

When examined with the naked eye, a thin layer of white cells will form, just on top of the red cell layer.  This is called the buffy coat.  The buffy coat contains different kinds of white blood cells that have separated out from the heavier red blood cells in the spun tube.

These white cells can be removed and examined on a microscope slide.  This is the buffy coat analysis.

About 15 years ago, a buffy coat smear was a common practice to stage mast cell tumors.  However, it has fallen out of favor.  The reason why is was done was to locate mast cell tumor cells in the circulation, which would give an indication that the tumor cells have spread throughout the body.  This is called mastocytemia (mast cells in the blood).

However, we do not rely on this test much any longer, and spending money on a buffy coat smear is usually not the best allocation of funds in a dog cancer budget for staging.  This is true even though the test is sometime still run. (Note that it can still be used to gauge treatment effects.)

The reason why the buffy coat smear is probably not a good use of funds for staging is that there are conditions that might increase the mast cells in the buffy coat when tumor spread is absent  (non-cancerous mast cells are normal members of the white blood cell family).

As it turns out, over 95% of dogs who don’t have mast cell tumors will be positive for mast cells in the buffy coat. Some parasites, skin conditions, and other issues may increase mast cell numbers.  Since the test will usually be positive, there is normally little point in running a buffy coat smear analysis to detect cancer spread.

Here is the abstract to read more.

For more information on mast cell tumors and other cancers in the dog, see the Dog Cancer Survival Guide.


Dr D


Leave a Comment

  1. mary on June 1, 2013 at 8:10 am

    My Bernese is 9 years old and has a very large the (size of a grapefruit ) mast cell mass on his abdomen. He also has one the size of a golf ball and another just starting. Vet said she doesn’t like the looks of this. Started him on steroids and benadryl. He doesn’t act like himself but doesn’t seem to be hurting. He also has Lyme disease since he was a puppy. I do not think he can stand surgery, and if it even reasonable to consider this with multiple sites happening.How do I know if its time to let him go. I don’t want to be selfish and yet I cannot bear the pain of putting him down. I know I feel so blessed to have had my boy for this many years..a lot of Berner owners don’t get this time. Please, if you can help me put this into perspective.
    Tks Mary

  2. Katy O'Loughlin on August 31, 2012 at 8:42 am

    Dr. Dressler,

    I recently found a small growth on my 3 yr old lab’s hind leg. I immediately took him to our vet who tested him and diagnosed him w a Mast Cell tumor. He also ordered a buffy coat and a CBC. My question is this: If the buffy test is hardly ever used anymore and, if this were your dog, what test would you recommend?? (BTW, his WBC & RBC both came back “Normal”)



  3. Jessi on May 17, 2012 at 9:11 am

    Dr. Dressler,
    I was wondering, are you boarded in oncology or radiation oncology by the ACVIM?

    • Dr. Demian Dressler on May 18, 2012 at 9:32 am

      Dear Jessi,
      No, nor am I particularly interested in the title or degree for myself. Dr. Sue, who writes for this blog and is coauthor of the Guide, is. Unfortunately “oncology” is usually defined as some combination of surgery, chemo and radiation with a wee bit if clinical attention on immunity. However, there are other facets of treatment beyond these that have application in dealing with cancer, although they are not part of what is termed “oncology” in our educational or clinical systems. Since these conventional tools thus far have not yielded in some cases the best outcomes for dogs and their people, finding venues of treatment that may improve longevity and life quality beyond these existing modalities is my main interest.
      Dr D

  4. Sharon on January 24, 2012 at 5:59 pm

    Boxers are known for Mast Cell Tumors (MCT). Early detection and removal are key. My Boxers have had 2-3 removed over their lifespan and they are 10 and 12 years of age now. MCT’S in areas like legs and feet are especially worrisome as there’s not a lot of tissue and it’s hard to get wide margins. Good luck with your Bernese.

  5. Christine on January 24, 2012 at 5:52 pm

    Is the Buffy Coat Smear process the same as when the vet wants to aspirate a tumor?

    • Dr. Demian Dressler on January 25, 2012 at 11:31 am

      Dear Christine-
      no, an fine needle aspirate samples the tumor and a buffy coat smear is a blood test that is not used any longer in most practices..
      Dr D

  6. Amber on September 2, 2011 at 3:52 pm

    I was just looking at your blog and was wondering if you could give me some advice. Today we just found out our 9 year old Bernese Mountain dog has a mast cell tumor on his right upper leg…and something has developed on his nose. The Vet did a blood test and the blood work came back normal (thank goodness). He was sending it off to see what grade the lump is but for now is having me do benadryl/tagament. He never gave me the choice to have the lump removed..wouldn’t that be the first option since his blood work was normal? He told me our dog probably only has 3 months to live but he doesn’t even know what grade it is?? Can removing it keep my dog around longer? I’ve heard mast cells are curable??
    Thank you

    • DemianDressler on September 6, 2011 at 8:35 pm

      Dear Amber,
      yes, it is very difficult to give predictions like this without a grade. Yes, surgery is a wise consideration, after another fine needle aspirate. Don’t forget the other steps in the Guide (diet, apoptogens, immune support, and so on). Bear in mind that grade 1 mast cell tumors have greater than a 90% cure rate after wide excision…you might want to get as much info as you can here (which you are doing!)

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