Chances are, if you’ve ever had the privilege of sharing your home with an unconditionally loving canine, you’ve come across a lump or bump either on top of or underneath their skin – which is one of the dog cancer warning signs.

For many of us dog-loving folks, this discovery may lead to a “freak-out” moment in which our minds automatically go towards the path of the dreaded “c” word – cancer.

More Benign BUT Worth Watching

Because the skin is technically the largest organ of the dog’s body, it is not surprising that the most common tumors that we see in dogs originate from the skin and subcutaneous (underneath the skin) tissue. According to Dr. Sue Ettinger, a world-renowned veterinary oncologist who is known by many as Dr Sue Cancer Vet, up to 40% of all submitted tissue samples to veterinary laboratories are of the skin. Luckily, though, most of the tumors that we find on or underneath the skin will end up being benign.

However, that doesn’t mean that we should be complacent when we find one of these lumps or bumps on our canine buddies. Between 20 and 40% of submitted tissue samples are reported to be cancerous, or malignant, after all!

So, with these statistics in mind, how concerned should we be when we find a lump or bump on our dog? Do we immediately call our trusted veterinary office and schedule an appointment to have the lump evaluated? Do we make note of the lump and wait to see whether or not it gets bigger? Or, do we forget about it if it doesn’t seem to be bothering our dog at all?

Dog Cancer Warning Signs Guidelines

Within the past several years, there has actually been a movement in the veterinary field to actually create guidelines for when to do further testing to determine what a lump or bump truly is. This movement was created by Dr. Sue Cancer Vet and is called the “See Something, Do Something.  Why Wait?  Aspirate!” ® Program. What her guidelines boil down to is that if you see a lump, bump, or lesion that is the size of a pea (which happens to measure 1cm wide) or larger and has been present for a month and hasn’t regressed or gone away, have it checked by your veterinarian!

This set of guidelines is easy for pet owners to remember and provides a systematic approach to dealing with new lumps and bumps that are being discovered.

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When you’ve utilized these guidelines and have determined that you need to have this newly-discovered lump evaluated, what should you expect from your dog’s veterinary visit? How will your veterinarian determine what that lump or lesion actually is?

How to Diagnose the Lump

Your veterinarian will talk with you about performing an FNA – or “fine needle aspirate” – of the lump. Your veterinarian will take a needle and syringe and remove some cellular material from the lump and place that material on a microscope slide. Sometimes, they may look at the sample in-house, and sometimes, they may prefer to send the sample out to be read by a board-certified pathologist. Even though veterinarians know what types of lumps – benign and malignant – can be found on a dog’s skin, they can’t tell us what those lumps actually are without testing them.  They can’t feel a lump and know whether or not it is cancerous. Some of the most innocent-looking lumps can be cancerous, and some of the ugliest-looking lumps can turn out to be benign!

Your veterinarian cannot determine what a lump or bump is with 100% certainty by just looking at it and feeling it.

If the FNA comes back as non-diagnostic (meaning that the cells were not able to be identified), your veterinarian may choose to either repeat the FNA or recommend that a small biopsy (or piece of tissue) of the lump be sent away for testing.

Dog Cancer Warning Signs Help Positive Outcomes

You may be wondering why your veterinarian would go through these steps – especially repeating an FNA or performing a small biopsy – rather than just recommending that the lump be removed. Remember, up to 40% of submitted canine lumps and bumps are reported to be malignant, or cancerous. When veterinary surgeons remove cancerous lumps, they typically try to remove a large section of “normal-looking” tissue surrounding them, as well. This reduces the chance for cancerous cells to be left behind and for tumor regrowth to occur.

However, the majority of submitted canine lumps and bumps are reported to be benign. These lumps and bumps typically do not behave aggressively within the skin and subcutaneous tissue and do not require such large resections of “normal-looking” tissue when removing them.

dog cancer warning signs - fine needle aspirate


One could argue that the FNA or small biopsy of the discovered lump could be skipped in favor of removal with wide surgical margins of “normal-looking” tissue, regardless of what the lump actually is. However, if the lump is actually benign, would you really want your dog to go through a lengthier surgery and recovery if it isn’t needed?  And, if the lump is actually benign, is it really necessary to remove it at all?  (In some cases, especially if the benign lump is growing rapidly or causing irritation to the dog, removing it would be recommended.)

Surgical Options

Your veterinary surgeon’s primary goal is to make your dog’s first surgery the only surgery he or she will need with regards to that newly-discovered lump, especially if it is cancerous.  Research has shown improved chances for a cure when a surgery to remove a cancerous lump only has to be performed once! If it comes back cancer, be sure to utilize our Canine Cancer Library for in-depth research.

Despite the fact that up to 40% of submitted lumps and bumps of skin origin are diagnosed as being cancerous, the majority of dogs can be cured with successful surgery alone! This is why knowing what a lump is before having it removed and then having successful surgical removal of a lump is so incredibly important!

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Now that you are well aware of dog cancer warning signs and are armed with the guidelines of when to have a lump or bump on your canine companion evaluated, it’s time to take a proactive approach to look for them!  If you have been following the National Canine Cancer Foundation for a while, you may have come across “Check Your Dog Day,” which was created by Chase Away K9 Cancer, an affiliate of the NCCF.

Check Your Dog Day

On the 14th of every month (or any same day of each month of your choosing), make a point to sit down with your canine buddy and check them all over for anything out of the ordinary for them. This is the perfect time to search for new lumps and bumps and to make a note of their location, size, and shape in a journal! By doing this each month, you may be alerted to something abnormal that you will want to have addressed by your veterinarian. By being diligent and proactive about your dog’s health, you may end up saving your best buddy’s life someday!

References: Ettinger, Sue. “Veterinary Oncology: What To Do With Lumps And Bumps On Dogs And Cats.” Today’s Veterinary Practice. July/August 2017

Other Articles of Interest:

Intestinal Tumors

10 Warning Signs of Cancer in Dogs

Common Chemotherapy Side Effects