Lipomas are common, usually harmless, tumors of fat that usually show up as a lump under the skin in middle-aged to older animals. Some pets will develop these tumors in their armpit region, between their legs, or around the neck, which can cause discomfort and/or lameness. You may see your pet exhibit an irregular gait, and/or reluctance to stand, walk upstairs, or go for their normal walks. This handout reviews the diagnosis, treatment, and prognosis of lipomas.