A lipoma is a noncancerous lump under the skin caused by excessive growth of fat cells. Lipomas may develop anywhere on the body but most commonly occur on the shoulders, neck, chest, back, buttocks, or thighs. They feel soft, smooth, and rubbery.
When pressed, they may move around under the skin. Lipomas grow very slowly, are painless, and do not usually cause any problems.
They are harmless and do not need treatment, although they can be surgically removed for cosmetic reasons.