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

The oncologist’s thoughts on what to do after the aspirate confirms mast cell tumor?

Updated: October 10th, 2018

In my recent blog, we discussed the aspirate that confirmed the diagnosis of mast cell tumor (MCT.)

Now there is a decision to make, should you have your dog staged to make sure the MCT has not spread, or should you proceed to surgery to remove the tumor and find out the grade?

Remember what I said in this MCT post, this is not a one-size-fits-all tumor, meaning there is not a checklist or single protocol for all dogs. MCT is a complicated cancer.

Some Guardians choose to stage the cancer without knowing the grade, because if it has spread they might not go through with surgery and may just do chemotherapy, or no therapy. Other Guardians want to remove the tumor, get the grade information, and then proceed with staging tests.

Why go to surgery?

If I have a dog with his first MCT and there is only one MCT, going to surgery is typically the next step. If possible, the goal of surgery is to remove the entire visible tumor along with a wide (usually 2 to 3 cm on all sides and a layer of tissue below) margin of surrounding normal tissue. The surgical margin must be confirmed clean with the pathologist’s report. The surgical biopsy also provides the grade. Grade is one of the most important prognostic (or predictive) factors for MCT. We will discuss that in the next blog.

Location location location!

Who should do surgery? If the tumor is large or in a region where getting clean margins will be challenging, I urge you to consider seeing a board-certified surgeon. A good example is a MCT on a leg – there’s just not a lot of tissue on these areas, especially the further down the leg towards the paw.

There is evidence that board-certified surgeons are more aggressive in their approach – in a good way; they typically remove more tissue, which results in cleaner margins and fewer cancer recurrences.

Wide excision — which means a big incision or cut — is the best way to achieve local tumor control (prevent cancer from recurring).  Surgeons actually measure around the tumor and mark the measurements on the skin before making incisions at surgery.

If the margins are not clean, I am likely to recommend a 2nd “scar revision” surgery. Which means the surgeon will have to go back and “revise” the scar — make it wider, basically, to get the tumor out completely. This is one reason I urge you to see a board-certified surgeon first, because your dog may require fewer surgeries. The first surgery is the best time to remove the entire tumor.

What if more than one MCT?

If there is more than one tumor, it is recommended to biopsy each one, because each separate tumor could be of a different grade and need a different course of treatment. If there are many tumors – more than four or five – I will often biopsy the two largest or the ones which have grown most quickly, depending upon the specific case, the location and size of the tumors, and my own discernment.

Do I stage prior to surgery and knowing grade? What does staging include?

It is always reasonable to look for spread prior to surgery. However, if your dog has a single Grade I tumor, further staging before surgery is probably not necessary.

But in all other cases – two or more tumors of any grade, a Grade II or III tumor, a recurrent MCT tumor, or lymph node metastasis – further staging is necessary before deciding upon a course of treatment.

If you did surgery 1st and the biopsy reported a Grade II or III MCT, I will recommend staging after surgery.

Staging should include at a minimum an aspirate of lymph nodes in the region of the tumor or tumors (even if they are of normal size) and an abdominal ultrasound to check for internal metastasis. A bone marrow aspirate may also be needed.

Why an abdominal ultrasound? In addition to spreading to the draining lymph nodes, MCT tends to spread to the liver, spleen, and sometimes internal lymph nodes; an abdominal ultrasound will reveal suspicious lesions or enlarged, infiltrated organs. If these are found, it does not necessarily mean that there is metastasis; the organs should be aspirated to confirm the situation. In most dogs, aspirates are done using ultrasound-guidance and can be done without sedation.

There is still some controversy about whether normal liver and spleen should be aspirated. But a recent study (Stefanello 2009), showed that normal-appearing organs can still be infiltrated with MCT, and dogs with aspirates that confirmed this sadly lived much shorter. So it is important to know that if the liver and spleen are normal on the ultrasound, this may be a false negative. While the procedure is safe, quick, and harmless in most cases, it is important to go through the pros and cons with your oncologist.

Next blog will be about the biopsy report, grade, and mitotic index. In the meantime, remember there is a lot more information on MCT, including staging tests, in the Guide.

Leave a Comment

  1. Mardy Array on April 29, 2020 at 4:57 am

    Good day. My beautiful dog son ~IBOO~ is diagnosed with stage 1 Liposarcoma,…not metastasized. But, he actually displayed twelve (12) tumors, 1 aspirated, 1 biopsied, and one removed w/clean margins.
    Never before Seen, this odd mutation of Liposarcoma (CT scan followed by MRI)stretching from his right scapula concentrated over mid right torso, reaching down right leg and to under belly, by Oncologists at Texas A & M small animal Hospitsl, practicing Prior Vet (27) years in Fla. keys, or our local vets here in San Antonio, Texas.
    Clearly, excising 12 tumors (albeit slow growing,…..How slow is slow?) with clear margins is medically impossible,.my pup is an Eskimo (toy), 14.8 lbs. there would be literally nothing left.
    IBOO is not yet 7 years old.

  2. Allison on November 29, 2018 at 6:11 pm

    We found a tumor on our 11 year old French Bulldog last month and had it removed last week. The biopsy results came back as a Stage III cancer with a MI of 15. Needless to say, we’ve been heartbroken. But, meanwhile, Ziggy seems happy and as active as always. According to tests they ran today, the ultrasound and x-rays showed no involvement in the organs and the lymph node and blood testing both came back as normal, so no spread yet. We started him on chemo today. It’s a bit confounding. We don’t want to have false hope. But is it possible to contain such a seemingly aggressive MSC with surgery (good margins) and chemo? I would have thought that to get to a Stage III, there would already be signs of metastasis. Does the cancer travel at a sub-clinical level and then just pop up quickly somewhere else? Thanks in advance!!

  3. Jenifer Wiley on November 12, 2018 at 3:42 pm

    Hi Dr. Sue,

    My 13.5yr old lab, Maddie, is a repeat offender with MCT. We had two surgeries last year, and now they are back with a vengeance. She has about 10 of them all over her body, including her head. I’m torn on what is best for her. The vet recommends taking a hands off approach because of her age, but the specialist encouraged me to have surgery. I’m a bit concerned about putting her under given her age. She is my baby who I love more than anything, and I just want her to live out her life happy and pain free, whatever that may mean. I’ve gotten conflicting advise and would love to know what you would recommend. Any advise is greatly appreciated. Thank you!

    • Dog Cancer Vet Team on November 13, 2018 at 7:21 am

      Hello Jenifer,

      Thanks for writing and we are sorry to hear about Maddie. It sounds like she has an amazing family :-). We’re not veterinarians here in customer support so we can’t offer medical advice. However, we can provide you with information based on Dr. Dressler’s writing

      Deciding on a treatment plan for your dog is a hard decision to make as there are so many things to take into consideration (finances, your dog’s personality, your personality, treatment options, age, etc), and there really is no one right fit because each dog, and their health situation is different–- this is where Treatment Plan Analysis can be really beneficial. Here’s an article on how to end treatment plan analysis paralysis and an article on Cancer Treatment at My Dog’s Age that you may find useful 🙂

      You also have to factor in your guardian type– do you want your dog to be as comfortable as possible? Are you okay with handling the side effects of particular treatments? How important is quality of life? Do you think she would be the same after another surgery? Here’s a link to an article on guardian types that you may find helpful:

      In the Dog Cancer Survival Guide, Dr. D writes that there are a number of treatment options (besides surgery, chemo and radiation) in the Full Spectrum Cancer Care that you could consider, under your vet’s supervision– Nutraceuticals, Diet, Brain Chemistry Modification, and Immune System Boosters and Anti-Metastics 🙂 Here’s an overview article on Full Spectrum Cancer Care that may be useful:

      You know yourself, and Maddie the best, so once you figure out what is most important for you and for her, and what type of guardian you are, you can then decide on a treatment plan 🙂

      We hope this helps 🙂

  4. Donna DiPaola on September 5, 2017 at 2:32 pm

    I am so upset. My 15 year old Sheltie mix was diagnosed with MCT around 4 weeks ago. The diagnosis was make after surgery to remove infected and necrotic tissue from her lower right rear leg. The biopsy reflected grade 2 and a mitotic index of 4. I was cautiously optimistic because of the index of 4. The stage came back as two. However the surgeon wasn’t able to get everything out. Her leg started to heal very quickly which surprised the doctors. Likewise they were surprised by the quick recurrence that we just noticed today. Now there is talk about amputation vs chemo and radiation. We had initially said we would consider local radiation once she was fully healed. She was over 90 percent healed when the reoccurrence happened. So I now think that we should have her liver and spleen aspirated to check for spread. If there is spread then the discussion will be very different. I am also confused because with all the communication with the drs I never understood that the initial tumor hadn’t been removed. My husband is the one who had been taking her back and forth to vet since I work long days. However in reading the reports snd speaking with the drs I understood that there was a chance or recurrence but not that the tumor or cells were still there. I would think that given that information the chance of recurrence would be 100 percent. I know my beloved dog is 15 but just had her annual check up and all was good. The dr was impressed and pleased how well she is or was
    She is eating and behaving normally and except for her limping is seemingly fine. Of course her humans know otherwise

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