Epidermoid (ep-ih-DUR-moid) cysts are noncancerous small bumps beneath the skin. They can appear anywhere on the skin, but are most common on the face, neck and trunk.
Epidermoid cysts are slow growing and often painless, so they rarely cause problems or need treatment. You might choose to have a cyst removed by a doctor if its appearance bothers you or if it’s painful, ruptured or infected.
Many people refer to epidermoid cysts as sebaceous cysts, but they’re different. True sebaceous cysts are less common. They arise from the glands that secrete oily matter that lubricates hair and skin (sebaceous glands).
Epidermoid cyst signs and symptoms include:
A small, round bump under the skin, usually on the face, neck or trunk
A tiny blackhead plugging the central opening of the cyst
A thick, yellow, smelly material that sometimes drains from the cyst
Redness, swelling and tenderness in the area, if inflamed or infected
When to see doctor
Most epidermoid cysts don’t cause problems or need treatment. See your doctor if you have one or more that:
Ruptures or becomes painful or infected
Occurs in a spot that’s constantly irritated
Bothers you for cosmetic reasons
Is in an unusual location, such as a finger and toe
The surface of your skin (epidermis) is made up of a thin, protective layer of cells that your body continuously sheds. Most epidermoid cysts form when these cells move deeper into your skin and multiply rather than slough off. Sometimes the cysts form due to irritation or injury of the skin or the most superficial portion of a hair follicle.
Nearly anyone can develop one or more epidermoid cysts, but these factors make you more susceptible:
Being past puberty
Having certain rare genetic disorders
Injuring the skin
Doctors can usually make a diagnosis by looking at the cyst. Your doctor may also scrape off skin cells and examine them under a microscope or take a skin sample (biopsy) for detailed analysis in the laboratory.
Epidermoid cysts look like sebaceous cysts, but they’re different. True epidermoid cysts result from damage to hair follicles or the outer layer of skin (epidermis).