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

Mast Cell Tumor Internal Spread

Updated: May 15th, 2024

It is important to tell whether or not a dog tumor has spread internally.

This question is not only very frightening for a dog lover, but also has some real medical ramifications.  So let’s take some time with this concept and mast cell tumors.

Mast cell tumors are very common in dogs.  They come in three grades (1, 2, or 3). Although they are all considered “potentially malignant”, the odds are that most grade 1 mast cell tumors are benign.

However, many grade 2 and all grade 3 are malignant and can be life-threatening.

Different cancers have their favorite spots to spread. Some spread to nearby locations, in the surrounding area next door to the tumor.  This is called local invasion. Some other cancers spread in the circulation, which is called metastasis. Some do a little of both.

These cancer cells have certain areas where they like to go.  The preferences seem to be created by cross-talk between the outside of the cancer “seed” cell and the area the cell settles in (the “soil”).  For more, click here and here.

Now, if we take mast cell tumors as an example, first we need to get our data.  We need to have found out that we are dealing with a mast cell tumor, and whether this tumor is a high grade 2 or a 3.  These have high metastatic rates.  For this reason, a biopsy should be done on mast cell tissue surgically removed to get the grade.

Once we know we have a mast cell tumor and the grade, we need to start the steps outlined in the Dog Cancer Survival Guide.  First, maintain composure so you can best cope most effectively with this news. Next, get your data and contemplate the different treatments available discussed in the Guide.

These include diet, chemo, surgery, radiation, immune support, life quality enhancement, supplements like Apocaps and others, pain control, antihistamines, antimetastatic treatments, and so forth. This analysis is done with help from your conventional vet, oncologist, and/or integrative vet primarily.

Now, the question that quickly arises is whether the tumor has spread or not.  It turns out that mast cell tumors have what is called a “tropism” or a preferential movement or attraction, towards certain organs.  These include first the spleen, then the liver, and also the lymph nodes and bone marrow.

Some areas of the body are visualized pretty well with X-rays. These include mainly bones, some other orthopedic structures,  and the lungs.

However, the soft tissues like the spleen and liver are best seen with an ultrasound. This is the tool that is used in pregnant women to evaluate developing babies.

So please make sure that when your dog has a mast cell tumor that has the potential for internal spread, ask for an ultrasound!


Dr D

Leave a Comment

  1. V on November 12, 2014 at 7:30 am

    My boston was diagnosed with grade III mast cell tumor on her back leg a year ago. We had the tumor removed, and put her on 8 treatments of chemo. A year later, she is still running around with lots of energy, which is very common for the boston breed. By the way, she is 9 1/2 years old. We do bring her into an oncologist about every 4-6 months to check her blood work, perform an ultrasound and take x-rays. I’ll be bringing her back in the next few weeks for her appointment. I’m still crossing my fingers that everything will be fine.

  2. Sarah Oliver on June 27, 2014 at 4:19 pm

    My cocker 11also,mast tumer in leg and chest.chest 1was rem0ved.but they said he has 6to9mts left ,im s000000 sad.but stayin strong,i knw u posted L0000NG TIME AGO.i was just wondering how long did yours live at the age 11 to after?PLEASE RESPOND., SARAH OLIVER

  3. Carol Taylor Starr on July 17, 2012 at 10:02 am

    Mammary tumor removed 5/7/12- grade II

    Mast Cell tumor- R front paw- no biopsy yet

  4. Mike on April 20, 2012 at 2:43 pm

    My nearly sixteen year old runt loveable Rotweiller started eating smaller portions,had stool that was soft and mucousey. An x ray today revealed a mass between the liver and the spleen. Ultrasound and prognosis follow and am praying it can be removed. He has arthritis in his pelvic region, has recently developed cataracts but that tail is a waggin every time he hears our voice or the touch of our hand on his back. My day has been a tear filled one sprinkled with hope. I adopted Bo from deplorable conditions while visiting Italy in 1996. His tiny body struggling to evade his bullying siblings reached out to me so I bought him and he became an American Canine shortly there after and brought lunconditional love to our California home. He has been to 18 states, loves to fish and….no matter the cost; his quality of life will be of the utmost consideration.

  5. Tammy M on June 23, 2011 at 5:57 am

    Dr. Dressler,
    my 13 year old yorkie mix was diagnosed a month and a half ago with a grade 2 MCT our normal vet tried to remove it but was unable to get it all. On to the specialist we went where then 2 MCT were removed which came back as grade 3 MCT. I have already spent over 2,000 on surgeries, vet visits, medicaitions. I do not want to do radiation or chemo. I don’t want to put my coco through anymore and we have twin 1 year old boys and are in no position to spend thousands more. I love my dog very much and want to keep her as healthy as I can for as long as I can. I have researched alot and have been giving her a huge range of things. I need to know if it is all ok and if there is anything else I should definitely be giving. I know I cannot cure her but just want to keep her with me again, as long as possible. I have had her all 13 years of her life and she is my baby.

    I currently am giving Krill oil
    Fish oil
    Flaxseed oil
    heartburn ( Tagamet)
    garlic oil
    k-9 imm. (which isn’t it the same as Fish oil)
    also some drops to help with immune system
    blackstrap molasses
    milk thistle
    I also feed her grain free, low carb food

    I know this sounds like alot, perhaps overkill? I just really love her and want her to feel good. I have also been walking her more since I read that cancer hates oxygen and a good way to keep her oxygenated is to walk her. Will any of this help or am I just getting my hopes up and wasting my money? PLEASE HELP

  6. Melissa on March 26, 2011 at 10:44 am

    Justus is a purebred English style Labrador. He has a great pedigree with no known illnesses. In January all of a sudden my daughter noticed a very large bulge on his side in the skin that connects his stomach to his leg. I took him to the vet and they did a needle aspiration which was inconclusive. Two days later he had the lump (which was bigger than a tennis ball) removed. Our vet thought it was suspicious so we decided to send it off for biopsy. It came back a grade 2 mast cell tumor but the cancer was confined to the inside of the tumor. No cancer cells were detected near or on the outside of the tumor. He turned 2 years old in February so he is still a baby. My vet said he has never seen this type of tumor in such a young dog. Until recently things seemed great but a few days ago he started to just lay around and today he vomited all his food. I am so worried that maybe the is more cancer inside him or that tumor spread and they didn’t realize it. I am taking him back to the vet. If you have any advice I would gladly listen.

    • DemianDressler on April 6, 2011 at 8:52 pm

      Dear Melissa,
      mast call tumors are very common. Search for mast cell tumors using the search bar on the right side of this blog. There is a lot of info in the Guide too.
      You will definitely find things that can help.
      Dr D

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