When to Tell the Vet About Your Dog’s Suspicious Lump

When it comes to new or growing bumps on your dog’s body, early veterinary intervention gives the best chances of a good outcome.

Different kinds of lumps and bumps can suddenly appear on your dog, but it doesn’t always mean they’re cancerous. By: ashyda

Yesterday, 2 dogs were booked in with the same problem, one after the other. The reason given in the chart was: “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 2 dogs had in common were concerned humans. They had both done the right action in bringing their dog to the vet to get to the bottom of things.

Lumps and Bumps

Most people find a lump and immediately think of cancer. Are all lumps cancer?


A lump is a swelling or area of tissue thickening. There are many reasons this could happen — of which cancer is only one — 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 it 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. By: Amigos3D

When to Worry

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 lump 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 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 drinking a lot, then let the vet know.

Questions From Clients

  • “But 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, 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 off to the vet it is.

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

How the Vet Knows What’s Wrong

During the physical exam, vets will check lymph nodes and closely examine the lump. They may well take the dog’s breed into account, since certain tumors are more common in some breeds than in others.

For example, mast cell tumors can be serious but can also present as fairly harmless looking skin lumps. If a vet sees a young Boston Terrier, Boxer or Golden Retriever that has a skin lump, they’re inclined to do more tests than for other breeds, even if the lump looks innocent.

An easy test to do at the clinic is a fine needle aspirate. This is where the vet places a needle into the lump and applies suction with a syringe. This collects a few cells from the lump, which can then be smeared onto a microscope slide.

The cytology, or cell types, present on the slide can give the vet valued clues as to what the nature of the problem is.

The Most Common Lumps and Bumps

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

  • 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 find lumps on their dogs:

The Take-Home Message

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 vet.

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 the pet checked by a vet.


This pet health content was written by a veterinarian, Dr. Pippa Elliott, BVMS, MRCVS. It was last reviewed Sept. 28, 2018.

Dr. Pippa Elliott, BVMS, MRCVS

View posts by Dr. Pippa Elliott, BVMS, MRCVS
Dr. Pippa Elliott, BVMS, MRCVS, is a veterinarian with nearly 30 years of experience in companion animal practice. Dr. Elliott earned her Bachelor of Veterinary Medicine and Surgery from the University of Glasgow. She was also designated a Member of the Royal College of Veterinary Surgeons. Married with 2 grown-up kids, Dr. Elliott has a naughty puggle called Poggle, 3 cats and a bearded dragon.

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