When Is It Okay To Monitor A Skin Tumor?

"Just monitor it."

Have you ever been told to "just monitor" a skin mass (tumor) on your dog by a veterinarian? How do you know if this is the right recommendation? How do you know when monitoring makes sense versus obtaining a diagnosis?

Many readers have been asking this question lately (if you've been wondering about this you're not alone) so I've decided to address it with this article.

The Big Picture

The answer to whether you should monitor your dog's skin tumor (versus obtaining a diagnosis) really comes down to whether you would treat your dog if the tumor were benign or malignant.

This is why a vet shouldn't decide this for you. Only you can know if you would treat, so you should make this decision.

A Few Things To Know First

The first thing I have to mention is that a vet cannot be certain that a tumor is benign just by "looking" at it. Many cancerous tumors look and feel EXACTLY the same as benign tumors, so the ONLY way to determine if a tumor is benign or malignant is by taking a sample. In most cases, a simple needle aspirate can yield a diagnosis.

If someone tells you that they can be certain a tumor is a lipoma just by looking at it, they're wrong. Yes, that tumor may most likely be a lipoma, but a subcutaneous mast cell tumor (malignant) will look and feel exactly the same as a lipoma. The only way to tell the difference is to perform a needle aspirate. In my opinion, it doesn't make sense to take the chance of being wrong when it takes just a few minutes to obtain the answer.

How To Decide

Sometimes if a tumor is benign and a patient is older, it might make sense not to pursue surgery, unless the benign tumor is bothering the patient. In the case of a benign tumor in an older patient, many families elect to monitor, especially if the patient has another aggressive disease (cancer, kidney or heart disease) which we expect to be life-limiting. If the benign tumor is not expected to affect quality of life or decrease the patient's length of life, surgical removal may not make sense.

Take a moment to think about the following scenarios and questions. They will help you decide whether you should have your dog's mass(es) aspirated (to obtain a diagnosis) or if you should continue to monitor.

If the mass was cancerous, would you elect to have surgery performed? (Provided that surgery would prolong the length of your dog's life, of course)

If the mass was cancerous and could be shrunk with steroids and/or low dose oral chemotherapy, thus prolonging your dog's life (instead of surgery), would you choose one of these options?

If you chose "yes" to either of the above questions, then you should obtain a diagnosis. If you would treat your dog if the mass were malignant (or if treatment could allow your dog to live longer), then monitoring doesn't make sense.

Monitoring just allows the tumor to grow larger and decreases the chance that surgery or other therapies will be successful in the future.

While you're monitoring, the mass will typically continue to grow (both benign and malignant masses will continue to grow; sometimes they stay stable in size for a bit, then grow after a few months) and one of two things might happen: (1) the mass may become too large for a successful surgery, (2) the tumor might metastasize (spread) to another organ, which then decreases your dog's lifespan.

I see this happen far too often. Families are often told to monitor a mass (without a diagnosis), then it becomes very large, and by the time they are referred to me, I not only have to break the news that the mass is cancer, but also that while they've been monitoring the tumor for the past few months, cancer has spread to another organ and now we can't do surgery and we don't have many options for their dog. This is always heartbreaking.

Thankfully, you're reading this article and will be able to decide for yourself whether monitoring makes sense for you or not.

Don't Forget

When dealing with malignant tumors, we are more likely to have a successful outcome when we intervene when the tumor is small.

If you think you would treat if your dog had a malignant tumor, you will have a higher chance of a successful outcome (successful surgery, etc) if treatment is started when the tumor is small.

The Case For Obtaining A Diagnosis Even if You Wouldn't "Treat"

What if you know you wouldn't perform surgery or treat with another form of medication to shrink or slow down the tumor - should you still get a diagnosis?

Well, a diagnosis could give you an idea of what to expect over the upcoming weeks and months. A diagnosis could help predict how slow or fast the mass will increase in size and if it is likely to metastasize or make your dog feel sick, painful, or unwell.

Some people will find this information very helpful, even if they don't plan to "treat" the tumor.

Logistical Considerations To Keep In Mind

In most cases, taking a needle aspirate to obtain a diagnosis of a tumor is a very quick and simple process (less than 5 minutes).

If your dog has many tumors, then a body map should be created. This is time-consuming and involves numbering, measuring, and sampling of each tumor. We use a drawing of a dog to keep track of the size and diagnosis of each tumor so that we can refer back to it at each visit.

Often, many tumors can be easily diagnosed in-house (especially benign fatty lipomas, etc). However, some samples might need to be sent to the lab for a diagnosis.

If your vet only has 15 or 30 minutes for a recheck visit, they won't be able to perform a body map during this time. You'll need to drop off your dog so that your vet (or oncologist) can be thorough and be certain that they can account for every mass.

If you're coming in for a wellness visit but want your vet to assess a mass, make sure you tell them that you want the mass assessed ahead of time (when the visit is scheduled). That way, they can be prepared (set up slides, syringe, needle, calipers, microscope) before you arrive.

If there are 30 minutes for the visit and you and your vet have spent the visit talking about how he's doing, his arthritis, making medication adjustments, giving vaccines, and on the way out (after 30 minutes have passed and the next client waiting for them) the new mass is mentioned...I hate to say it, but they might be more likely to say "let's monitor" because the time for the visit has been used up and they don't want to upset their next client by making them wait.

So if there's a new mass, make this a priority and alert them when you schedule the appointment. It is often very challenging for a vet to get everything done in the short amount of time they have to see each patient, so giving them adequate "head's up" will be helpful and will allow your dog to receive the best care possible.

If you notice a new mass, it's best to schedule a separate visit to have the mass aspirated and NOT WAIT until your dog is due for vaccines or a dental or a wellness visit.


If your vet isn't confident or comfortable aspirating the skin mass or isn't able to obtain a diagnosis, just get a second opinion from a colleague or oncologist who can get you answers.

It makes the most sense to monitor if you know what type of tumor you're monitoring (if you have a diagnosis).

Again, there is significant benefit to knowing if a tumor is malignant, even if you know that you won't proceed with surgery. If a dog has a malignant tumor, it may respond (shrink) to oral steroids or low dose oral chemotherapy.

Having a diagnosis will give us a better idea of how the tumor will behave (what signs your dog might experience if the tumor spreads/metastasizes, which organs the tumor may metastasize to, how long your dog may live without treatment) and will help us understand how to keep your dog as comfortable as possible over the upcoming months, which is always the goal.

Dr. Lori Cesario

Board Certified Veterinary Oncologist

PS: I'm happy to now offer online oncology consultations. Learn more about how this service can help by visiting the Vet Cancer Consultants site.

A few other articles you might enjoy...

(1) Dog Breeds and Their Associated Cancers

(2) Mast Cell Tumors - The Great Imitator in Canine Cancer

(3) How To Tell If Your Dog is Nauseous

© 2021 Canine Cancer Academy | Terms | Privacy | Disclaimer | Support | Account