As of 2015, doctors do not know the cause of fatty tumors, or lipomas, in humans, according to Healthline. Fatty tumors tend to run in families, so there is likely a genetic component.
Lipomas often develop in adults between the ages of 40 and 60, but they can occur in people of any age, explains Mayo Clinic. Fatty tumors rarely develop in children. People with certain disorders, such as adiposis dolorosa, Cowden syndrome and Gardner's syndrome, are at higher risk of developing more than one fatty tumor.
A lipoma is fatty tissue that grows beneath the skin, states Healthline. Lipomas can develop anywhere on the body, but they often develop on the back, neck, shoulders, arms, thighs and abdomen. Located just beneath the skin, lipomas are small, soft, easy to move and pale or colorless. They are not usually painful unless they grow into nearby nerves. Lipomas are classified as benign tumors by the American Cancer Society, meaning they do not spread and are not lethal.
Lipomas do not require treatment if they are not bothersome, notes Healthline. They do not respond to home treatments, such as cold or hot packs. If a lipoma is large or painful or if multiple lipomas are present, a doctor can use surgery, liposuction or steroid injections to shrink or remove them.