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Dogs and Lipomas
Are all fatty tumors benign?

Expanding on the topic of tumors discussed last week, this blog is devoted to lipomas, aka fatty tumors. Of all the benign growths dogs develop as they age, lipomas are one of the most common. They arise from fat (lipid) cells and their favorite sites to set up housekeeping are the subcutaneous tissue (just beneath the skin surface) of axillary regions (armpits) and alongside the chest and abdomen. Every once in awhile lipomas develop internally within the chest or abdominal cavity. Rarely does a dog develop only one lipoma. They tend to grow in multiples and I’ve examined individual dogs with more lipomas than I could count.

Should lipomas be treated in some fashion? In the vast majority of cases, the answer is a definite, “No!” This is based on their benign, slow-growing nature. The only issue most create is purely cosmetic, which the dog could care less about!

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

1. A lipoma is steadily growing in an area where it could ultimately interfere with mobility. The armpit is the classic spot where this happens. The emphasis here is on the phrase, “steadily growing.” Even in one of these critical areas there is no reason to surgically remove a lipoma that remains quiescent with no discernible growth.

2. Sudden growth and/or change in appearance of a fatty tumor (or any mass for that matter) warrant reassessment by a veterinarian to determine the best course of action.

3. 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/or treated with radiation therapy.

4. Occasionally a lipoma grows to truly mammoth proportions. If ever you’ve 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 tumors 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 catch on to the mass’s rapid growth so as to surgically remove it before it becomes enormous in size and far more difficult to remove.

How can one prevent canine lipomas from occurring? No one knows. Anecdotally speaking, it is thought that overweight dogs are more predisposed to developing fatty tumors. While I’m not so sure I buy this, I’m certainly in favor of keeping your dog at a healthy body weight.

Does your dog have a lipoma, or two or three?



Nancy Kay, DVM, Dipl., American College of Veterinary Internal Medicine, is a 2009 recipient of AAHA's Animal Welfare and Humane Ethics Award and author of Speaking for Spot.


Courtesy of Flickr Creative Commons/Heather Kennedy

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Submitted by charlene | July 3 2014 |

My Misty has lipomas. She's ten, and has always had one. More importantly, she's had one that comes back and comes back and comes back. It's been removed three times now that I'm aware of (we got her as a young adult and it had already been removed at least once).

The first time we had it removed the vet commented on strands of fat that seemed to go other places, that she had pulled out (but probably didn't get them all). The second time was a year ago, and the vet knew the last surgeries findings, and kept on digging until he found one of those fat strands attached to her pelvis. The lipoma was actually three masses, he said, and it was growing near the base of her tail. We always worried it could interfere with her spine; turns out it had infiltrated a lot of muscle mass and could have eventually made her incontinent too. It's been a year now and it doesn't seem like it's coming back. Finally.

I knew that a recurring "infiltrative" lipoma, which is what this seemed to be, was more likely to be liposarcoma, but luckily Misty's was negative.

Misty has other "senior dog" type lipomas now, and because of the other I worry about them, but they're normal, slow growing, and "loose".

Given her history with an infiltrative lipoma, do you think we should pay closer attention to these? We don't really live in a place with good veterinary care (the last surgery we went two hours to a specialist).


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