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Suspicious Lump on Your Dog? Here’s When to Tell the Vet.

When it comes to any suspicious lump on your dog, early veterinary intervention gives the best chances of a good outcome.

Suspicious Lump on Your Dog
Different kinds of bumps and suspicious lumps on your dog can suddenly appear, but it doesn’t always mean that they are cancerous. Photo: ashyda

Two dogs were booked yesterday with the same problem, one after the other.

The reason given in the chart? “Client concerned as a lump has got bigger.”

But whereas one dog needed no further action, the other dog faces referral to a specialist. Why? Because one lump was a harmless fatty bump, but the other was a potentially serious tumor.

What these dogs had in common were concerned humans. They had both done the right action in bringing their pet to the veterinarian to investigate suspicious lumps on the dogs.

Found a Suspicious Lump on Your Dog

Most people find a suspicious lump on their dog and immediately think of cancer.

Are all lumps cancer? No!

A lump is a swelling or area of tissue thickening. There are many reasons a dog can get a “suspicious” lump. For example:

  • A cyst: This is a lump filled with fluid that is secreted from the lining of the cyst.
  • An abscess: This is a discrete collection of pus, usually the result of a bite or scratch.
  • Bruising and thickening: This is a result of a knock or blow.
  • Ticks or foreign bodies: A colleague of mine once diagnosed a “tumor” as a boiled sweet stuck in the dog’s fur.

But what if the suspicious lump on your actually is cancer?

Not all lumps are the same.

There’s a spectrum of seriousness that ranges from “nothing to worry about” to potentially life-threatening. But while it’s the latter that sticks in the mind, the former are more common.

Cancers are also divided into:

  • Benign: The lump grows bigger but won’t spread to other parts of the body.
  • Malignant: These aggressive lumps have the potential to spread to the organs.
Warts are generally harmless for dogs. Photo: Amigos3D

When to Worry About a Suspicious Lump on Your Dog

Get any new lump — or any existing lump that changes in some way — checked out.

There are certain signs that can tell you that an urgent visit to the vet is for the best.

These include:

  • Rapid growth: A suspicious lump on your dog that’s growing quickly can cause problems in 2 ways. First, this may be a hint it’s more aggressive, and second, a large lump is more tricky to remove than a small one.
  • Redness: Some more serious lumps on dogs release chemicals that cause tissue reaction and inflammation. If the bump looks sore or bothers the dog, then get it checked out as a matter of urgency.
  • An ailing pet: Again, some tumors release chemical factors that affect general health. If the dog lacks energy, is losing weight, has tummy troubles or is drinking a lot, then let the vet know.

Common Questions About Suspicious Lumps on Dogs

“What if I can lift the lump up in the skin, away from the tissues underneath?”

This is a good sign, since aggressive lumps often invade the deeper tissues.

But — and it’s a big “but” — some more serious lumps on dogs, such as mast cell tumors, can mimic less harmful ones, so even this sign is no guarantee.

“The dog has had the lump for years, and it’s never changed. Should I worry?”

Again, no change is generally considered a good sign because aggressive cancers are just that and will grow quickly.

However, check those lumps and bumps monthly.

  • Take a photo, if necessary, so you have a record.
  • Better still, photograph the lump next to a ruler so you know the exact size.

If the lump starts to grow, becomes red or changes character, then it is a suspicious lump on your dog — and off to the vet it is.

Check your pet’s lumps often for any changes. Photo: winterseitler

Why You Should Listen to Your Vet About Pathology

“I found a lump, and I’m in a panic.”

I hear this all the time. I also hear a follow-up comment at times that makes me unhappy: “Just take it off, and I don’t want to know what it is,” says the worried client. Oh, boy. Now I’ve got some convincing to do.

Most growths that warrant removal also warrant analysis. This analysis is called a biopsy or pathology.

It’s important to get a diagnosis on a growth, to give it a “name’ so that we know what we are dealing with, but many people balk at this idea. For the purposes of this article, assume that lump, bump, growth, mass and tumor are interchangeable terms.

What Clients Sometimes Say

“If it’s bad news, I’d rather not know.”

I hear this a lot when someone declines to send out a biopsy. Well, what if it’s good news?

  • Many growths or tumors can be cured when surgical removal is complete.
  • Did you know we use the term “tumor” even when describing a benign growth, such as a fatty tumor, commonly called a lipoma? Tumor means an abnormal growth of tissue. It is not synonymous with cancer. There can be benign tumors and malignant tumors.
  • Some growths might look nasty and have you and your vet concerned, but the diagnosis may paint a more favorable picture.
  • If you don’t get a diagnosis, you live with worry and concern. An answer stops the “What if?” syndrome.

“If it’s cancer, I won’t put my pet through chemo.”

There is so much wrong with this kind of thinking. First of all, recommending chemotherapy following a growth removal is not all that common.

If — and that’s a big if — some sort of drug therapy is recommended following surgery, we usually choose chemo drugs that have low toxicity and are tolerated well. If the drug doesn’t agree with the pet, we can always stop the drug, usually without doing lasting harm.

If a biopsy does yield bad news, many people in the “I wouldn’t do anything drastic” camp change their tune when follow-up treatment could mean a longer life or cure for their pet.

“No biopsy for my pet — it’s too expensive.”

Lab fees can be costly, pathology fees costing upward of $200.

The information obtained, however, can tailor a follow-up treatment plan. Knowing the type and behavior of the tumor your pet had removed helps us make decisions in the future.

Finding out the status of your pet’s condition can inform decisions made about their care. Photo: StockSnap

Cytology, Biopsy, Pathology

There are a number of ways to get information about a growth, both before and after removal.

Fine Needle Aspirate (FNA)

Basically, a fine needle aspirate is a fancy way of saying we stick a needle in a lump, squirt the contents of the needle on a slide, stain the slide and look at the splat!

Looking at cells like this is called cytology. Hopefully, the splat (aspirate) contains cells that give us a clue about the type of growth we’re dealing with.

FNAs are quick, easy and inexpensive, but they yield limited information. Many FNAs give us an idea that a growth is probably benign or probably cancerous but tell us little about how that growth will behave or the severity of the cancer.


A biopsy usually refers to a sampling of a growth taken prior to removal of the entire growth and having it analyzed by a veterinary pathologist.

Many biopsies can be done with only a local anesthetic. In an ideal world, it would be great to biopsy every growth and know the diagnosis prior to surgical removal.

The pros of doing a biopsy are many. The biopsy can suggest how much of a pre-surgical work-up should be done and tell the surgeon how conservative or radical to be at the time of surgery.

Certain tumors, for example, due to their aggressive behavior, require a very wide excision to get the best chance at a cure. Having a reliable biopsy in advance prepares the client, surgeon and patient for a basic or more radical surgery.

The cons generally have to do with putting the animal through an additional procedure, the cost and the possibility that the small section of tissue submitted for biopsy may not be representative of the entire mass.

Rarely, excessive bleeding can occur.


Histopathology refers to the preparation and microscopic examination of tissue samples.

Usually, we use the phrase “sending out for pathology” when we remove an entire mass and send that mass with surgical margins to the pathologist. The tissue (growth, mass, tumor, etc.) is the biopsy sample, and histopathology is the analysis.

Sending an entire mass to the lab for pathology gives us the best diagnosis and tells us if our margins are clear of tumor cells. The pathologist will also comment on the specific character of the cells in the mass, stage the tumor if applicable and often give an opinion about prognosis.

Sending Out the Biopsy

When clients understands the important medical information and prognostic factors that can be learned from pathology, they frequently agree to the added expense.

Occasionally, a client declines the biopsy, even when I strongly recommend it be done. I tell these people on the emotional or financial fence that their pet’s tumor is “fixed” in formalin. The sample is not time-sensitive and can go out to the lab next week or next month.

The bottom line: When your vet recommends the pathology, please do it.

The Most Common Lumps and Bumps on Dogs

This isn’t meant as an exhaustive list but as an idea of the types of lumps that are most common in dogs.

  • Warts: The extra skin tags or lumps of skin are usually harmless but may bleed if caught by a brush or collar.
  • Fatty lumps, or lipomas: These are localized fat deposits that are common in older dogs. Again, they are of no significance other than if they grow so large they become a nuisance.
  • Mammary cancer: This is more common in older female dogs who are not spayed.
  • Mast cell tumors: These can range from those lumps where removing them solves the problem to potentially aggressive lumps that can spread. They’re common in younger dogs, and surgical removal is the best option.
  • Sebaceous cysts: Common in older animals, some cysts are filled with a white, almost toothpaste-like secretion. They are of no concern other than being a nuisance.
  • Histiocytomas: Another skin tumor that occurs in young dogs, these ones do eventually subside of their own accord. However, the problem is mast cell tumors can mimic histiocytomas, so removal is the safest option.

These vets provide great information and advice for those who have found suspicious lumps on their dogs:

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Final Thoughts on Suspicious Lumps on Dogs

Check your dog regularly for lumps and bumps.

If you find a new lump or an old lump is growing, get them checked by a veterinarian.

Should the lump be something worrisome, early intervention gives the best chances of a good outcome. So don’t go into denial, but keep calm, carry on and get your pet checked by a vet.

vet-cross60pThis pet health content was written by a veterinarian, Dr. Pippa Elliott, BVMS, MRCVS, with contributions from another veterinarian, Dr. Debora Lichtenberg, VMD. It was last reviewed Aug. 14, 2019.

If you have questions or concerns, call your vet, who is best equipped to ensure the health and well-being of your pet. This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis or treatment. See additional information.