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|Classification and external resources|
|Classification and external resources|
A sebaceous cyst (pron.: / /) is a term that loosely refers to either epidermoid cysts (also known as epidermal cysts; L72.0) or pilar cysts (also known as trichilemmal cysts; L72.1). Because an epidermoid cyst originates in the epidermis and a pilar cyst originates from hair follicles, by definition, neither type of cyst is strictly a sebaceous cyst. The name is regarded as a misnomer as the fatty, white, semi-solid material in both of these cyst entities is not sebum, but keratin. Furthermore, under the microscope neither entity contains sebaceous glands. In practice, however, the terms are often used interchangeably.
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The scalp, ears, back, face, and upper arm, are common sites for sebaceous cysts, though they may occur anywhere on the body except the palms of the hands and soles of the feet. In males a common place for them to develop is the scrotum and chest. They are more common in hairier areas, where in cases of long duration they could result in hair loss on the skin surface immediately above the cyst. They are smooth to the touch, vary in size, and are generally round in shape.
They are generally mobile masses that can consist of:
The nature of the contents of a sebaceous cyst, and of its surrounding capsule, will be determined by whether the cyst has ever been infected.
With surgery, a cyst can usually be excised in its entirety. Poor surgical technique or previous infection leading to scarring and tethering of the cyst to the surrounding tissue may lead to rupture during excision and removal. A completely removed cyst will not recur, though if the patient has a predisposition to cyst formation, further cysts may develop in the same general area.
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Sebaceous cysts generally do not require medical treatment. However, if they continue to grow, they may become unsightly, painful, infected, or all of the above.
There are three general approaches used: traditional wide excision, minimal excision, and punch biopsy excision.
The typical outpatient surgical procedure for cyst removal is to numb the area around the cyst with a local anaesthetic, then to use a scalpel to open the lesion with either a single cut down the center of the swelling, or an oval cut on both sides of the centerpoint. If the cyst is small, it may be lanced instead. The person performing the surgery will squeeze out the keratin (the semi-solid material consisting principally of sebum and dead skin cells) surrounding the cyst, then use blunt-headed scissors or another instrument to hold the incision wide open while using fingers or forceps to try to remove the cyst intact. If the cyst can be removed in one piece, the "cure rate" is 100%. If, however, it is fragmented and cannot be entirely recovered, the operator may use curettage (scraping) to remove the remaining exposed fragments, then burn them with an electro-cauterization tool, in an effort to destroy them in place. In such cases the cyst may or may not recur. In either case, the incision is then disinfected and, if necessary, the skin is stitched back together over it. A scar will most likely result. In some cases where "cure rate" is not 100% the resulting hole is filled with an antiseptic ribbon after washing it with an iodine based solution. This is then covered with a field dressing. The ribbon and the dressing are to be changed once or twice daily for 7–10 days after which the incision is sewn up or allowed to close by secondary intention, i.e. by forming granulation tissue and healing "from the bottom up."
An infected cyst may require oral antibiotics or other treatment before and/or after excision.
An approach involving incision, rather than excision, has also been proposed.
Another method of treatment involves placement of a heating pad directly on the cyst for about fifteen minutes, twice daily, for about 10 days (depending on size and location of the cyst) to promote drainage.
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