The primary sign of a fatty cyst, also known as a lipoma, is a soft, rubbery and small movable bump that can be felt under the skin, explains WebMD. Fatty cysts do not cause pain and typically do not enlarge, but the cysts may grow slowly.
Fatty cysts may be bothersome if the size or location of the cyst is visible to others, according to WebMD. The cause of fatty cysts is unknown as of 2015, but researchers have deemed heredity as a contributing factor as well as minor injuries that can trigger growths. People who are overweight or obese are not always at risk for fatty cysts.