Epidermoid cysts

Symptoms and causes

Epidermoid (ep-ih-DUR-moid) cysts are harmless small bumps beneath the skin. They 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 if it bothers you, breaks open, or is painful or infected.

Epidermoid cyst

Illustration of epidermoid cyst on different skin colors. Epidermoid cysts occur most often on the face, neck and trunk.

Epidermoid cyst signs and symptoms include:

• A small, round bump under the skin, often on the face, neck or trunk
• A tiny blackhead plugging the central opening of the cyst
• A thick, smelly, cheesy substance that leaks from the cyst
• An inflamed or infected bump

The surface of the skin, also called the epidermis, is made up of a thin, protective layer of cells that the body sheds nonstop. Most epidermoid cysts form when these cells move deeper into the skin rather than shed. Sometimes this type of cyst forms due to irritation or injury of the skin or a hair follicle.

Epidermal cells form the walls of the cyst and then secrete the protein keratin into it. Keratin is the thick, cheesy substance that can leak from the cyst.

Anyone can develop an epidermoid cyst, but these factors make it more likely:

• Being past puberty.
• Having a rare, inherited condition called Gardner syndrome.
• Injuring the skin.

Potential complications of epidermoid cysts include:

• Inflammation. An epidermoid cyst can become painful and swollen, even if it's not infected. An inflamed cyst is hard to remove. Your doctor is likely to postpone removing a cyst until the inflammation subsides.
• Rupture. A cyst that breaks open can lead to a boil-like infection that needs prompt treatment.
• Skin cancer. In rare cases, epidermoid cysts can lead to skin cancer.