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Facts about the skin from DermNet New Zealand Trust. Topic index: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z


What is a cyst?

A cyst is a lesion that contains fluid or semi-fluid material, so a cyst is fluctuant. Cutaneous cysts are harmless, sac-like growths in the deeper layers of the skin. It is not known why cysts appear. Some people get many cysts because of genetic and / or environmental influences.

What types of cyst are there?

Cutaneous cysts include:

Cysts that are not surrounded by a capsule are better known as pseudocysts. Pseudocysts include:

Benign cysts may sometimes be confused with skin cancers, especially a nodulocystic basal cell carcinoma. Rare malignant cysts include malignant proliferating trichilemmal cyst.

Pilar cyst
Pilar cyst
Pilar cysts
Pilar cysts
Multiple epidermal cysts
Large epidermal cyst
Large epidermal cyst

More images of epidermal and pilar cysts and images of vulval cysts ...

What are ruptured cysts?

Ruptured cysts are red, painful epidermal cysts. They may discharge yellow pus. The contents of the cyst penetrate the capsular wall and irritate the surrounding skin.

Occasionally bacteria enter the cyst and cause an infection which resembles a boil. When this happens, antibiotics, such as flucloxacillin, and minor surgery to incise the cyst and drain the pus may be needed to relieve the pressure and pain.

What is the treatment for cysts?

Small cysts (eg. less than 5 mm) don't usually need treatment, but can be readily removed by a minor surgical procedure if desired. Larger ones are usually removed because they are unsightly or because they have ruptured. It is best to avoid surgery while the cyst is actively inflamed, because surgical site infection is likely.

Cysts are treated by making a small surgical opening into the skin and removing the sac (excision biopsy). This is done under local anaesthetic and may require stitches, which are removed a few days later.

It may be difficult to extract the cyst in entirity. The cyst may then recur. Recurrence of pseudocysts is particularly common.

Related information

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Author: Dr Amanda Oakley Dermatologist, Hamilton New Zealand. Updated 22 February 2014.

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If you have any concerns with your skin or its treatment, see a dermatologist for advice.