Epidermoid cyst
- Reviewed by Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing
What is it?
An epidermoid, or epidermal, cyst is a small, movable lump under the skin. It forms when surface skin cells move deeper into the skin and multiply. These cells form the wall of the cyst and secrete a soft, yellowish substance called keratin, which fills the cyst. If the wall of the cyst is ruptured, the keratin is discharged into the surrounding skin, which causes irritation and inflammation.
The cyst may remain small for years, or it may continue to get larger. These cysts are rare in children but common in adults. Cysts are not cancerous.
Symptoms
A cyst is a movable, dome-shaped, smooth-surfaced mass that varies in size from a few millimeters to several centimeters (from less than a quarter of an inch to more than 2 inches). Epidermoid cysts can occur on almost any skin surface.
Diagnosis
Your doctor can examine the swelling and tell you if you have a cyst.
Expected duration
A cyst may disappear on its own or remain indefinitely.
Prevention
There is no way to prevent epidermoid cysts.
Treatment
Asymptomatic epidermoid cysts usually do not need treatment. If it becomes red or tender from inflammation or infection, a clinician can make a small incision in the skin, empty the contents of the cyst and remove its wall.
When to call a professional
If you have a new swelling on your skin that lasts for more than two weeks, contact your doctor. If it is painful or rapidly enlarging, you should arrange for sooner medical evaluation.
Prognosis
The outlook for epidermoid cysts is excellent. Many cysts have no symptoms and some will go away on their own. Cysts can return. If your cyst is problematic, your doctor may decide to drain it or remove it. This does not usually lead to any complications or side effects.
Additional info
American Academy of Dermatology
https://www.aad.org
About the Reviewer
Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing
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