Epidermoid cysts are noncancerous small bumps beneath the skin. They can appear anywhere on the skin but they are most common on the face, neck and trunk.
Epidermoid cysts are slow growing and usually painless and rarely cause problems or require treatment. A cyst can be removed if its appearance is bothering, it’s painful, ruptured or infected.
Epidermoid cysts are often referred to as sebaceous cysts, but there is a difference between the two. Sebaceous cysts are less common and arise from the glands that secrete oily matter that lubricates hair and skin (sebaceous glands).
Symptoms of epidermoid cysts include:
- Small round bump beneath the skin (face, neck or trunk)
- Tiny blackhead plugging the central opening of the cyst
- Thick yellow, foul-smelling material that drains from the cysts
- Redness, swelling and tenderness in the area due to inflammation or infection.
The surface of the skin (epidermis) is made up of a thin, protective layer of cells that the body sheds continuously. Epidermoid cysts form when these cells travel deeper into the skin and multiply rather than fall off.
The epidermal cells form the walls of the cyst and secrete the protein keratin into the interior. The keratin is a thick, yellow substance that sometimes drains from the cyst. The abnormal growth of epidermal cells may be due to a damaged hair follicle or oil gland in the skin.
Risk factors for epidermoid cysts include:
- History of acne
- Being past puberty
- Injuring the skin
- Certain rare genetic disorders
Possible complications of epidermoid cysts include:
- Inflammation (tender and swollen with or without infection)
- Rupture (may lead to a boil-like infection)
- Infection (painful abscess)
- Genital discomfort (genital epidermoid cysts may lead to painful intercourse and urination)
- Skin cancer (rare)