An epidermal cyst, or sebaceous cyst, is a sac beneath the outer layer of the skin that is filled with a cheeselike, greasy material (sebum). These cysts most often appear on the scalp, ears, face, back, or scrotum and are caused by plugged ducts at the site of a hair follicle.
Signs and symptoms include a bump or lump under the skin that is:
Medical treatment is usually not needed if the cyst does not cause symptoms. A cyst can be removed if its appearance causes embarrassment or if it becomes injured or infected. If the cyst is infected, antibiotics may be used.