A cyst is an abnormal growth consisting of a closed sac filled with fluid or solid material. The material within the cyst is usually produced by the cells that make up the lining, or wall, of the cyst. Cysts form for a variety of reasons, depending to some degree on the tissue involved. Some cysts that form in the adrenal glands are caused by bacterial infections or by parasites.
The most common type is the sebaceous cyst. Also called epidermoid, pilar, and vulvar cysts, they are harmless, slow-growing bumps under the skin, often appearing on the scalp, face, ears, back of the neck, back, upper chest or groin area (typically the vulva or labia). They are usually rounded, non-tender and of varying size.
Any redness, tenderness, or increased temperature of skin over area may indicate an infection. Grayish white, cheesy material from the cyst (if drained or squeezed) may have a bad odor. The cause is usually unknown.