The Animal Medical Center’s Usdan Institute for Animal Health Education provides our clients and the broader community with important, relevant, and timely animal health information. A dog owner reached out to the Institute for information on lipoma, a fatty tumor found most commonly in dogs. I will recap my answer to their question here.

What is a lipoma?

A lipoma is the most common skin tumor found in dogs and is a benign accumulation of fat cells. Some dogs never have one, and others can be very lumpy because of multiple lipomas. Because medical terms can be confusing, be sure you don’t confuse lipoma with lymphoma. Lymphoma is a malignant tumor of lymph nodes and is the most common malignant canine tumor treated by AMC oncologists.

What does a lipoma look and feel like?

A lipoma is a mass under the skin, which you may notice because the lipoma causes the fur to stick up funny, or you run into the lump when you are petting your dog. Lipomas are usually soft and easily movable; they are not attached to the underlying body wall. Some lipomas can attain giant proportions and cover the entire side of your dog, without causing any medical issues. Veterinarians cannot rely on how the skin mass looks or feels to determine if the mass is a lipoma. Mast cell tumors and soft tissue sarcomas, two potentially malignant tumors, also develop under the skin and can feel soft and squishy just like a lipoma. I have seen dogs with ten lumps, nine are lipomas and the tenth is a nasty mast cell tumor.

Should I have my dog’s lipomas removed?

The presence of a lump on your fur baby is worrisome to many dog families, but the vast majority of lipomas never cause a problem in a dog. Occasionally, a lipoma becomes very large and interferes with ambulation. These are often found in the armpit, and removal improves the dog’s quality of life immeasurably.

Are lipomas ever malignant?

The word, lipoma, implies a benign tumor, but there is a malignant version of lipoma, a liposarcoma. A liposarcoma is not a lipoma gone bad, but a tumor arising from juvenile fat cells. Dogs affected by a liposarcoma can have a good prognosis, but usually need a major surgical procedure to completely remove the tumor.

My dog is really lumpy, now what?

Lipomas are easily diagnosed via cytology. Cytology can sort out the difference between mast cell tumors and soft tissue sarcoma as well. Talk to your veterinarian about any lumps you find on your dog. If the lumps are sometimes hard to find, use a permanent marker or white-out painted on the fur to make finding them easier during your pet’s examination.