Lipomas in Dogs and Cats What is That Lump Under Your Pet’s Skin?

When most people find a bump under their pet’s skin, their mind goes to the worse case scenario: cancer. And while it’s true that some lumps will be cancerous, many others will be benign and harmless. Lipomas -- soft, moveable masses of fatty tissue under the skin -- are the latter case, and they are very common in dogs.

What Causes Lipomas in Dogs and Cats?

Though the causes of lipomas in dogs and cats are not well understood, their formation appears to be related to the aging process, as they show up most frequently in middle-aged and senior dogs (especially females). They also commonly appear in overweight dogs, which may be due to the large number of fat cells they have.

The dog breeds that are most likely to develop lipomas include Cocker Spaniels, Dachshunds, Poodles, and Terriers.

While lipomas are less common in cats, they do sometimes occur in older cats and cats with feline leukemia.

Symptoms of Lipomas in Dogs and Cats

Most owners notice a lipoma on their pet while petting or grooming them. Lipomas are soft and round bumps under the skin that can appear anywhere on the body (though in dogs, they are often located on the belly or torso). They are usually not painful, but they can be if they are particularly large or located in an area where they are interfering with or becoming irritated by movement (for example, in the armpit).

Most dogs and cats who have had one lipoma will go on to develop others.

Diagnosing Lipomas in Dogs and Cats

If you ever notice a lump or bump under your pet’s skin, contact your veterinarian. This is true even if your pet has had a lipoma before.

Your veterinarian will check for others lumps and perform a fine needle aspiration, a type of biopsy in which a very thin needle is inserted into the area to check for cancerous cells. If the results of the fine needle aspiration are inconclusive, your veterinarian may need perform another biopsy that involves more invasive tissue removal.

Treatment for Lipomas in Dogs and Cats

If testing reveals that your pet’s lump is in fact a lipoma, your veterinarian will likely recommend a “wait-and-see” approach. You’ll want to keep an eye on your pet’s lump, watch for other lumps, and visit your vet regularly so that they can monitor the lump and check for any changes. In most cases, no further treatment will be required. However, surgery is an option if the lump is interfering with your pet’s movement or causing them irritation.

Some types of lipomas may be more serious.

Infiltrative lipomas are those that invade surrounding tissues, moving into the bones or muscles and causing functional problems. Even though they are benign, they can really hinder a pet’s movement. Treatment usually involves surgery or surgery and radiation therapy. Ideally, the lipoma should be removed entirely. However if it cannot be completely removed for whatever reason, radiation therapy can help to control its spread.

Liposarcomas are rare, malignant fatty tissue tumors that can appear on any part of the body and do not necessarily start out as a benign lipomas. Depending on the grade of the tumor, they may be dangerous and capable of spreading to the lungs and other organs. The primary treatment option is surgery, though radiation therapy and chemotherapy are also sometimes employed. Even though liposarcomas are not very common, they represent how important it is to have each and every new lump examined, even if past lumps have been innocent.

Sources

Lipomas (Fatty Lumps)
Fatty Skin Tumors in Dogs
What Causes Lipomas in Dogs?