Cysts

A cutaneous cyst is a lesion that contains fluid or semi-fluid material so is fluctuant. Cysts are harmless, sac-like growths in the deeper layers of the skin. They form from the lining of a hair follicle that gets blocked. It is not known why cysts appear, nor why some persons get many of them.

Types of cyst include:

• Acne comedones (whiteheads)
• Acne cysts (large uninflamed acne lumps)
• Dermoid cyst (a developmental inclusion cyst)
• Milium/a (tiny surface white balls often found on the cheeks after sun exposure or following an injury). Milia can easily be squeezed out.
• Epidermal cysts (soft cheese-like contents)
• Trichilemmal cysts (scalp cysts, often multiple and familial, arising from hair root sheath)
• Pilar cysts (firm white content)
• Steatocystoma multiplex (multiple inherited cysts on trunk)
• Digital myxoid cyst (cyst at the base of a nail)
• Pseudocyst of auricle (cyst on the external ear)
• Labial mucous cyst (cyst in the lip)
• Apocrine hidrocystoma (clear jelly-like cyst of eyelid)
• Bartholin's cyst (vulval swelling)

Benign cysts may sometimes be confused with skin cancers, especially a nodular or 'cystic' basal cell carcinoma.

The epidermal cyst sac is filled with a soft, whitish brown material that sometimes oozes out onto the skin's surface. This material, which is keratinous debris (dead skin cells), smells like rotten cheese.

Cysts

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

More images of cysts and images of vulval cysts ...

Ruptured cysts

Cysts can get inflamed if the contents of the cyst rupture into the surrounding skin. This makes them red and painful, and they may discharge yellow pus.

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

Treatment

If you have a cyst, ask your dermatologist's or doctor's advice.

Small cysts (eg. less than 5 mm) don't usually need treatment, but can be readily removed by a minor surgical procedure. Larger ones are usually removed because they are unsightly or because they have been inflamed.

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, removed a few days later.

Very occasionally the cyst recurs and needs further treatment.