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When It Comes to Tumors, Lipomas Are Big Softies

Veterinarian Dr. Nancy Kay on why these fatty tumors aren’t always cause for concern.

by Nancy Kay, DVM
Updated December 21, 2021
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Samantha Gehrmann // Stocksy

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Of all the benign growths your pup might develop as they age, lipomas (a.k.a. fatty tumors) are one of the most common. Older dogs often have at least one or two cutaneous (within the skin) or subcutaneous (just beneath the skin surface) lumps and bumps. They’re common by-products of the aging process. The good news is, most of these tumors are benign and totally harmless. But there are a small number of malignant (cancerous) masses — which is why it’s important to have your veterinarian inspect any new lumps and bumps your dog develops.

Lipomas in dogs often give pet parents severe anxiety when there are multiple or very large masses present. So it’s a good idea to get to know what your dog’s healthy, normal body looks like by performing regular at-home physical exams. Generally, the smaller a cancerous growth is at the time of treatment, the better the outcome.

What Are Lipomas?

Lipomas are very common fat-based masses, or tumors, seen on middle-age and senior dogs, and they’re generally benign. They arise from fat, or lipid, cells and are typically found in the subcutaneous tissue of axillary regions, like the armpits, and alongside the chest and abdomen — though occasionally lipomas develop within the chest or abdominal cavity. 

Dogs rarely develop only one lipoma. They tend to grow in multiples, sometimes more than you can count. Fatty tumors that grow between the muscles are called infiltrative lipomas and when malignant, they’re called infiltrative liposarcomas. While lipomas usually grow slowly, each one is different and some progress much more quickly.

Should Lipomas Be Treated?

Lucky for you, in the vast majority of cases, the answer is a definite, "No!” Lipomas in dogs are generally not treated because of their benign, slow-growing nature. Lipomas don’t go away on their own, but the only issue most create is purely cosmetic — and trust us, your dog couldn’t care less. 

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Lipomas in Dogs: When To Seek Veterinary Care

There are a few exceptions to the general recommendation to let sleeping lipomas lie. A fatty tumor deserves more attention in the following situations:

1. The location of a lipoma interferes with mobility.

If a lipoma is steadily growing in an area where it could ultimately cause problems with a dog's mobility, you might choose to remove it before it gets too large. The armpit is the classic spot where this happens. That being said, even in one of these critical areas, you’ll likely need to have the lipoma surgically removed only if it’s growing large.

2. The tumor grows suddenly and/or changes in appearance.

Notice either and you should have a vet check out your dog right away and recommend the best course of action.

3. The lipoma is actually an infiltrative liposarcoma.

Every once in a great while, a fatty tumor turns out to be an infiltrative liposarcoma rather than a lipoma. These are the malignant black sheep of the fatty tumor family. Your veterinarian will be suspicious of an infiltrative liposarcoma if the fine needle aspirate cytology reveals fat cells yet the tumor feels fixed to underlying tissues. (Lipomas are normally freely moveable.) Liposarcomas should be aggressively surgically removed and sometimes treated with radiation therapy.

4. The lipoma expands to truly mammoth proportions.

If you’ve ever looked at a dog and thought, “Wow, there’s a dog attached to that tumor!” chances are you were looking at a lipoma. Such massive growths have the potential to cause the dog discomfort. They can also outgrow their blood supply, resulting in possible infection and drainage from the mass. The key is to surgically remove the tumor before it becomes enormous and far more difficult to remove.

Can Lipomas in Dogs Be Prevented?

No one knows because risk factors include a complicated mix of environment, genetics, diet, and care. It’s thought, though, that overweight dogs are more predisposed to developing fatty tumors. Keeping your pup at a healthy body weight isn’t a cure-all, but it’s a good thing to strive for.

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Nancy Kay Author

Nancy Kay, DVM

Nancy Kay, DVM is a board-certified specialist in the American College of Veterinary Internal Medicine. She was a recipient of AAHA’s Animal Welfare and Humane Ethics Award and is the author of Speaking for Spot.