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

Dog cancer: What is Micrometastasis and Why Do We Care?

Updated: December 18th, 2018

I get a lot of inquiries that relate to whether a cancer is gone after it is removed, or what will be the outcome.

Sometimes these are tough to answer, and the reason is micrometastasis.

Micrometastsis occurs when a cancer spreads from a site, but the spread is not detectable by the usual means available.  Only a few cells take off, traveling perhaps in the circulation to set up shop elsewhere in the dog’s body. So few cells spread, that they are undetectable.

So you have someone like me take the tumor out, for example, and the borders are examined by a pathologist to see if the margins are “clean” (no cancer cells at the edge, they are all located near the center of the removed piece, suggesting complete removal).  Your path report says “complete excision” (complete removal).

Say though, that you are faced with the diagnosis of a malignant melanoma, a Grade 3 mast cell tumor, an osteosarcoma, an advanced squamous cell carcinoma,  a large hemangiosarcoma, or some other kind of canine cancer with a known tendency to spread.

Suppose your vet or oncologist was very thorough and did all that could be done to see whether there was evidence of spread, and all the tests were negative.  But your vet or oncologist is still pessimistic.  Why?

Micrometastasis.  The cancer did spread, but only a few cells.  These can sneak up on us later, turning up as cancers that were not there at the time we checked, but were there later.

This is why we are sometimes talking about steps beyond surgery when there is no evidence the cancer has spread. We want to make sure we are addressing the known tendency of these cancers to take off, even when the tests looking for spread are negative.

Best to all,

Dr D


Leave a Comment

  1. Susan Kazara Harper on April 25, 2014 at 2:23 am

    OK, this needs to be checked. Have you examined the paw to see if there are any thorns or other objects stuck in between the pads? Hairy feet are more difficult to check. Will your dog let you pick up the paw and hold it? Does he or she whimper? Walk on it? There’s no way to diagnose anything over the internet, you do really need to get your dog checked at the vet. You can always ask if you can pay in installments for any treatment. Vets have a business to run, but they also understand. Don’t worry, because that won’t get you anywhere. Get it checked out, be honest with your vet practice and ask how you can manage this. You don’t want to leave these symptoms without treatment. Hopefully it will be a very easy fix. The weekend is coming and you probably will have a better chance to sort it out before weekend hours Good luck!

  2. Ixtlan01 on April 23, 2014 at 7:16 pm

    By the way my dog now that he has that hole seems disarienred like, he lifts a front paw and looks like is having dificulty setting the paw down, im cery worried for my dog, please help us!!

  3. Ixtlan01 on April 23, 2014 at 7:12 pm

    My retriever had a lump on the side, a vet. Saw it said was norhing to worry since there was no aparent pain, yesterday the lump erupted abd is now an open hoke a quarter sized. What can it be?? Im on a financial situation, only half an income right now, we love iur dog but we can’t expend what we dont have, any ideas of what can it be???

    • Susan Kazara Harper on April 25, 2014 at 2:17 am

      Hi there, If it was a lump just attached to the skin (did it move around with the coat?) and it’s now erupted there is a good chance that it was an abscess. Did some stuff like puss come out? Maybe your dog got a slight injury that caused a local infection and it’s now burst. BUT, honestly only a vet who looks at your dog can confirm this. And even if it’s an abscess, it still needs to be cleaned and checked. A retriever has long coat hair and this can mat around the hole and complicate things if you leave it. Please call your vet’s office and explain the situation. It shouldn’t cost much to have it looked at. Have you checked whether there are any other vet options in your area? Sometimes it’s possible to find assistance. I really understand the limited income situation. Equally, a dog is an expense you’ve got to allow for with good food (doesn’t have to be expensive) and being prepared for vet bills. The good news is you’ve got a great friend who wants to cuddle all the time whether you’re rolling in dough or having a lean streak! Please check with your vet, and, good luck!

  4. Debbie Elliott on July 17, 2012 at 1:44 pm

    Great on the Mali at 4 years! Our 11 year old shep collie mix had a splenectomy 4 weeks ago to remove a small hemangiosarcoma that was discovered early (while looking for something else. ) Treatment options presented: Adriamycin, 5 rounds, low dose pill, or both. Normal prognosis without treatment, only 3 months! They said that 10 to 20 % of dogs make it to one year with treatment. Any suggestions? Would tumeric be helpful as an adjunct? We are leaning towards the low dose pill with herbal supplementation. He has been on vegan Evolution diet for 7 years.
    Thanks much.

  5. Kathy on November 2, 2008 at 8:55 am

    My Tigger had mass removed last Aug 07 from liver dx. hepatocelluar carcinoma. ( CLEAN MARGINS.) Had rechecks every 8 weeks and in May 08 mass came back in liver right in the middle. Surgery was not advised so far TIGGER HAS HAD TWO CHEMOEMBOLIZATIONS TO SHRINK THIS TUMOR.

  6. Ilene and Mali on October 30, 2008 at 3:03 am

    Cathy, my Mali was dx splenic HSA on 12/20/2004. Her spleen ruptured and required an emergency splenectomy. We did 5 rounds of Adriamycin chemo and still do chemo maintenance and antiangiogenesis. She has great quality.
    While doing chemo, we did chest x-rays, abdominal ultrasounds and CBC’s every month to monitor how she was handling her chemo and to see what may or may not be lurking. After her chemo, we went every 2 to 3 months. After year 2 post dx, we went every 3 to 4 months. We are nearing year 4 post dx and now go every 6 months for scans, but still do the CBC’s and a physical exam every 3 months, as she is on so many meds and supplements. Throughout all this time, we gone in for needle aspirates and/or removal of suspicious lumps and bumps.
    Best to you and your Lab from me and my Lab.

  7. Dr. Demian Dressler on October 29, 2008 at 11:37 am

    I should also mention this should include complete physical examinations and aspirates or biopsies of any enlarged lymph nodes or further masses found.

  8. Dr. Dressler on October 29, 2008 at 11:36 am

    I assume it was removed??
    I cannot give recommendations for specific animals on this blog. However, generally speaking, for dogs with hemangiosarcomas that were removed, and are judged stable by the vet working on the case, one protocol could be ultrasounds and chest films every 3-4 months, along with CBC’s,full chemistry panels and urinalysis at the same interval. Of course this is dictated on the individual patient’s needs. Good luck!!

  9. Cathy Banks on October 29, 2008 at 11:15 am

    You wrote:
    This is why we are sometimes talking about steps beyond surgery when there is no evidence the cancer has spread.

    Having a 12yo Lab with a huge hemangiosarcoma 3 mos ago, what tests do you recommend, and at what inntervals? Currently, we are doing a chest xray, abdominal utz, and a detailed blood check.

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