A lipoma is a benign (non-cancerous) growth of fat cells that develops under the skin. It is usually soft, movable, and painless. Lipomas grow slowly over time and can appear anywhere on the body, but they are most commonly found on the neck, shoulders, arms, back, and thighs. Causes The exact cause of lipomas is unknown, but they may be linked to: Genetics (family history of lipomas) Injuries (though not always proven) Certain medical conditions (e.g., adiposis dolorosa, Cowden syndrome) Sympto