A Lipoma is a benign fatty lump. They are very common in older, middle-aged dogs. Overweight female dogs are especially prone to developing Lipomas. Certain dog breeds may be at risk, including, but not limited to: Doberman Pinschers, Schnauzers (miniatures), Labrador Retrievers, and mixed breeds. They can also appear in cats and horses, but not as often.
Lipomas are usually just under the skin, but they can be locally invasive, meaning they have meshed with muscle or connective tissue. Lipomas can also have additional blood or connective tissue as part of the growth. These growths can appear anywhere on the body, but they are most frequently located on the belly (mid-chest and down) and upper legs.
Any and all lumps should be checked out by your veterinarian, regardless of how your pet is acting. Your vet will assess the location, duration, firmness, and size. A needle aspirate may also be taken to look at what type of cells make up the lump.
A needle aspirate is when a sterile needle is inserted into the lump and the plunger withdrawn, providing suction to collect cells from the lump. This is not painful, and not usually even noticed by most pets. Your vet will then place the collected cells on a microscope slide, stain them, and take a look under the microscope.
Should a Lipoma Be Surgically Removed?
Provided your veterinarian has performed a needle aspirate and is certain that it is indeed a lipoma, most vets recommend a watch-and-wait approach. The lump should be checked at regular intervals, to make sure there haven't been any cellular changes. Large lumps, especially those under a limb or in another location to interfere with movement or function, should be removed as soon as possible.
Check All New Lumps
If a new lump has appeared on your pet, it could be another benign lipoma. Dogs that form lipomas are prone to forming more as time goes on. However, each new lump needs to be checked out by your veterinarian (and the "known" lumps rechecked at least annually), as there are other, more serious tumors that can feel like a Lipoma, such as a cutaneous mast cell tumor.
Are Lipomas Ever Malignant?
Yes, although rare, there is a fatty tumor called a liposarcoma, and that is malignant. Metastasis is rare, but due to their nature (infiltrative) they are difficult to fully remove, and recurrence is common.