How Long to "Watch and Wait" - Dog Cancer Blog

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

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How Long to “Watch and Wait”

Last week I told you about two recent cases in which the tumors were too big for surgery by the time they came to me. I also promised to give you some guidelines about how long to wait when your vet says “let’s just monitor this.” Too many lumps and bumps are being monitored for too long … so this post contains some guidelines.

The Vaccine-Associated Feline Sarcoma Task Force of the American Veterinary Medical Association has guidelines based on their work looking at sarcomas occurring at vaccination sites. While these guidelines were created for cats originally, and the first rule refers to vaccine injection sites, in my experience these guidelines apply to dogs, as well.

According to this “1-2-3 Rule,” you should get a lump or bump aspirated right away if any of the following is true for your dog:

  1. The mass is increasing in size one month after injection.
  2. The mass is greater than two centimeters in diameter.
  3. The mass persists for longer than three months

So, if your dog’s lump or bump is increasing in size after a month, bigger than two centimeters (just under an inch), or hasn’t gone away after three months – get it checked!

 Phew: It’s Benign.

Hopefully, the mass will turn out to be benign. If that’s true, it may not need to be removed right away.

A lot depends upon where a benign tumor is located. If it’s causing pain, it might be keeping your dog uncomfortable. On the other hand, if removing it would be a complicated surgery – it’s near a joint, or it is on the lower limb where there just isn’t much tissue to work with – it might not be worth removing.

If it does need to be removed, most benign masses require smaller surgeries. We don’t worry as much about getting wide margins. Also, sometimes the surgery can be combined with another procedure that requires anesthesia. For example, if your dog is getting his teeth cleaned and undergoing anesthesia for that, your vet might offer to remove the benign tumor at the same time. The risks of anesthesia are real, too, after all.

Oh, no. It’s malignant.

If the aspirate comes back indicating the mass is malignant, remember that it is often better to get a small surgical biopsy to determine the type of malignant tumor and the grade before going for a curative surgery.  I may also recommend staging diagnostics first, before the curative surgery. This is a complicated subject, I’ve written about in several posts, including this one on mast cell tumors.

 Surgery Might Be All You Need

Surgery is often all we need to treat many cancers, so please, do not wait too long to get a lump or bump checked out. Remember Tiger and Tulip? Both could have had great prognoses, if the tumors were removed with clean margins the first time, when the tumor was small enough to get out. Now, surgery would harm more than help, and they are stuck with radiation, which is less effective for measurable sarcomas, or chemotherapy, which is much less effective for primary tumors than it is for metastasis.

As your dog’s guardian, make sure you read biopsy reports. Tiger’s mom was unaware of the dirty margins that were reported on the biopsy from his first surgery a year ago. If she’d known then about the incomplete margins, and that it meant his tumor was more likely to recur, she would have had more time to address the situation.

What About Recurrence?

That said, even with a clean margin reported on the biopsy, tumors can still regrow from microscopic cancer cells we don’t see in the biopsy. So we must all monitor for regrowth. Some tumors, like Tiger’s, are in a location that you can see. Others, like those inside the mouth or inside body cavities, you might need to check with imaging tests or sedated exams.

If your dog’s tumor is malignant and you have it removed, recheck it every two to three months after the surgery. Early detection of recurrence is key to addressing it with the highest possible chances of success.

The Bottom Line

Please, don’t watch and wait as a mass grows, because there is a point at which it will be too big to address. Have your vet measure and document the size of the tumor, so you can compare growth. Aspirate or biopsy that mass, if needed. And make sure you find out about the margins after surgery. Were they wide enough for that tumor type? If not find out if there can be a scar revision (second surgery), or if radiation can prevent regrowth, or chemotherapy can slow recurrence. Be proactive. Check with an oncologist, and please, don’t monitor for too long.

Remember the “1-2-3” Rule and get that lump or bump aspirated right away if any of the following is true for your dog:

  1. The mass is increasing in size one month after injection.
  2. The mass is greater than two centimeters in diameter.
  3. The mass persists for longer than three months

All the Best,

Dr. Sue

About the Author: Susan Ettinger, DVM, Dip. ACVIM (Oncology)


Susan Ettinger, DVM. Dip. ACVIM (Oncology) is a veterinarian oncologist at VCA Animal Specialty & Emergency Center in New York, and the co-author of The Dog Cancer Survival Guide: Full Spectrum Treatments to Optimize Your Dog's Life Quality and Longevity.

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