Lipoma (Fatty Tumor)

What is it?

A lipoma is a noncancerous tumor made of fat. It usually grows under the skin, though it can appear anywhere, even inside the abdomen. Lipomas that grow between muscle layers are called infiltrative lipomas. A rare malignant form, liposarcoma, seldom spreads but needs more extensive surgery. Many middle-aged and older dogs have more than one lipoma.

What signs should I watch for?

Most lipomas are soft, movable lumps under the skin. Some stay the same size for years; others grow large. A lipoma in the armpit, between the legs, or around the neck can cause discomfort or lameness, such as an odd gait, reluctance to stand, climb stairs, or go for walks.

How is it diagnosed and treated?

Your veterinarian can usually confirm a lipoma with a fine needle aspirate, a quick sample of cells taken with a small needle. If results are unclear, a biopsy may be needed, and CT scans help plan surgery for infiltrative lipomas or suspected liposarcoma. Surgical removal is the most effective treatment and is easiest while the lump is small. Steroid injections into the lipoma have shown some promise when surgery is not an option.

Can it be prevented, and what's the outlook?

• There is no known way to prevent lipomas.
• Once removed, they seldom come back, though new ones may appear.
• Have every new or changing lump checked, since a needle sample is the only way to tell a lipoma from other lumps.