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Epidermoid Cyst

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Updated April 02, 2014

Epidermoid cysts are the most common type of skin cyst. They can occur anywhere on the body but tend to occur more on the face or upper trunk. Other names for an epidermoid cyst include:

  • Epidermal cyst
  • Infundibular cyst
  • Epidermal inclusion cyst
  • Keratin cyst
  • Sebaceous cyst

Epidermoid Cyst Appearance

An epidermoid cyst has a cyst wall that is made of skin cells found in the epidermis. This cyst wall is like a balloon that projects down into the second layer of the skin, the dermis. This balloon, or cyst wall, makes keratin -- a protein found in skin, hair, and nails -- and is white, cheesy, or firm.

A typical epidermoid cyst looks like a raised, round bump. If you touch it, you can typically feel the cyst wall and move the cyst around under the skin fairly easily. Often there is a small opening on the surface of the skin that may look like a scab, but that opening may be so small that it's difficult to see.

Epidermoid Cyst Rupture

Epidermoid cysts usually don't cause problems unless they get very large or the cyst wall ruptures, exposing the inside keratin to the surrounding tissue. This is a problem because the contents of an epidermoid cyst are very irritating to the tissue around the cyst. A ruptured cyst can get red, swollen, and painful. If this happens, it's best to see your doctor instead of trying to "pop" the cyst. Sometimes an inflamed cyst needs to be opened to let it drain; if so, your doctor may recommend treating it with warm compresses for a few days to help the cyst continue to drain. Other times, in lieu of opening the cyst, treatment may involve antibiotics or an injection with a corticosteroid (usually triamcinolone).

When to Have a Cyst Removed

An epidermoid cyst doesn't have to be removed if it's small, doesn't hurt, and hasn't gotten red and swollen. I recommend the removal of a cyst to my patients for the following reasons:
  • It's in a place where it gets irritated rubbing against clothing or jewelry.
  • It's located in a place that is visible and getting larger quickly.
  • It frequently gets inflamed or infected.

How Epidermoid Cysts Are Removed

If an epidermoid cyst needs to be removed, it's important that the whole cyst wall is taken out. Remember, it's the cyst wall that makes the keratin contents. If the cyst is merely opened and the contents are drained, the cyst wall is still inside and it will start making more keratin, causing the cyst to "return."

An epidermoid cyst is usually removed by making an incision over the cyst and removing most of the contents. Then, the whole cyst wall is separated from the surrounding tissue and removed. If the incision is large enough, it may need to be sutured closed.

Sources:

Habif, Thomas. "Benign Skin Tumors." Clinical Dermatology, 4th Edition. Ed. Thomas Habif, MD. New York: Mosby, 2004. 645.

Stone, Mary Seabury. "Cysts." Dermatology. 2nd. Ed. Jean Bolognia. New York: Mosby, 2008: 1681-83.

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