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Causes
By Mayo Clinic staffThe surface of your skin (epidermis) is made up of an extremely thin, protective layer of cells that your body continuously sheds. Most epidermoid cysts form when these surface cells, instead of exfoliating normally, move deeper into your skin and multiply. Most often, this occurs in areas where there are small hair follicles and larger oil glands (sebaceous glands), such as your face, neck, upper back and groin.
The epidermal cells form the walls of the cyst, and then secrete the protein keratin into the interior. The keratin is the thick yellow substance that sometimes drains from the cyst.
Several factors can lead to this abnormal proliferation of cells, including:
- Damage to a hair follicle. Each hair grows from a follicle, a small pocket of modified skin in the dermis, the layer of skin just below the epidermis. Follicles damaged by injuries, such as abrasions or surgical wounds, can become blocked by surface cells.
- A ruptured sebaceous gland. Located just above the hair follicles, sebaceous glands produce sebum, the oil that lubricates your skin and coats each hair shaft. These glands are easily ruptured by inflammatory skin conditions, especially acne, making them a likely site for epidermoid cysts.
- Developmental defect. Epidermoid cysts can begin in a developing fetus when stem cells intended to form skin, hair or nails become trapped in cells forming other tissues.
- Heredity. Epidermoid cysts can develop in people with Gardner's syndrome, a rare genetic disorder that causes growths in the colon, or basal cell nevus syndrome, an inherited disease that leads to several serious defects.
- Lynch PJ. Vulvar neoplasms and cysts. In: Black M, et al. Obstetric and Gynecologic Dermatology. 3rd ed. St. Louis, Mo.: Mosby; 2008. http://www.mdconsult.com/book/player/book.do?method=display&type=bookPage&decorator=header&eid=4-u1.0-B978-0-7234-3445-0..10023-2--s0020&uniq=130671532&isbn=978-0-7234-3445-0&sid=827482137#lpState=open&lpTab=contentsTab&content=4-u1.0-B978-0-7234-3445-0..10023-2%3Bfrom%3Dtoc%3Btype%3DbookPage%3Bisbn%3D978-0-7234-3445-0. Accessed April 9, 2009.
- Goldstein BG, et al. Benign neoplasms of the skin. http://www.uptodate.com/home/index.html. Accessed April 9, 2009.
- Epidermal cysts. The Merck Manuals: The Merck Manual for Healthcare Professionals. http://www.merck.com/mmpe/sec10/ch127/ch127c.html. Accessed April 9, 2009.
- Benign skin tumors. In: Habif TP. Habif: Clinical Dermatology. 4th ed. St. Louis, Mo.: Mosby; 2006. http://www.mdconsult.com/das/book/body/130671532-17/0/1195/141.html?tocnode=51442353&fromURL=141.html. Accessed April 9, 2009.
- Epithelial cysts and sinuses. In: James WD, et al. Andrews' Diseases of the Skin: Clinical Dermatology. 10th ed. Philadelphia, Pa.: Saunders Elsevier; 2005. http://www.mdconsult.com/book/player/book.do?method=display&type=bookPage&decorator=header&eid=4-u1.0-B978-0-7216-2921-6..50033-0--cesec136&displayedEid=4-u1.0-B978-0-7216-2921-6..50033-0--cesec137&uniq=130671532&isbn=978-0-7216-2921-6&sid=827486768#lpState=open&lpTab=contentsTab&content=4-u1.0-B978-0-7216-2921-6..50033-0--cesec136%3Bfrom%3Dtoc%3Btype%3DbookPage%3Bisbn%3D978-0-7216-2921-6. Accessed April 9, 2009.
- Pisharodi L, et al. Fine-needle aspiration biopsy. In: Gnepp DR. A Diagnostic Surgical Pathology of the Head and Neck. Philadelphia, Pa.: Saunders Elsevier; 2009. http://www.mdconsult.com/book/player/book.do?method=display&type=bookPage&decorator=header&eid=4-u1.0-B978-1-4160-2589-4..00015-2--s0360&uniq=130671532&isbn=978-1-4160-2589-4&sid=827488065#lpState=open&lpTab=contentsTab&content=4-u1.0-B978-1-4160-2589-4..00015-2%3Bfrom%3Dtoc%3Btype%3DbookPage%3Bisbn%3D978-1-4160-2589-4. Accessed April 9, 2009.
- Goldstein BG, et al. Dermatologic procedures. http://www.uptodate.com/home/index.html. Accessed April 9, 2009.
- Penneys NS, et al. Common benign cutaneous growths: Seborrheic keratoses, cherry hemangiomas, and epidermoid cysts. American Academy of Dermatology. http://www.aad.org/education/students/benign_cutan_growths.htm. Accessed April 9, 2009.
- Gibson LE (expert opinion). Mayo Clinic, Rochester, Minn. April 16, 2009.
