Patient Information Leaflet
Keratoacanthoma
What are the aims of this leaflet?
This leaflet has been written to help you understand more about keratoacanthomas (KAs). It tells you what they are, what causes them, what can be done about them, and where you can find out more about them.
What are keratoacanthomas?
KAs are relatively common skin growths. They are unusual in that, though they are not cancerous, initially they behave and can look like one form of skin cancer (a squamous cell carcinoma). They grow quickly over the first few weeks but do not spread to other parts of the body. Indeed, if left alone, they will usually go away, although sometimes they may take as long as a year to do so.
What causes keratoacanthomas?
Their precise cause is not known. Factors that sometimes play a part include heavy sun exposure, contact with some chemicals, smoking, infection with some strains of wart virus, a suppressed immune system, and minor injuries to the skin.
KAs are more common in fair than in dark-skinned individuals, and in men than in women. They are rare under the age of 20 and become more common with age.
Are keratoacanthomas hereditary?
Usually not, though multiple KAs are a part of a few rare inherited conditions.
What are the symptoms of a keratoacanthoma?
Usually there are none apart from their cosmetic appearance, as they tend to be on exposed skin.
What does a keratoacanthoma look like?
KAs crop up most often on the face, and less often on the backs of the hands and forearms. Usually they are single and surrounded by normal skin.
The first sign is a small round skin-coloured or red bump. Sometimes people squeeze it as it may look like a spot, but no pus comes out. As it grows, a KA takes up its characteristic appearance. The small bump becomes firm, raised and dome-shaped with a smooth surface and a central plug made of brown keratin (the material of which hair and the outermost layer of skin is made). If the plug comes out, a crater will remain, giving the KA the appearance of a ‘mini-volcano’. As a KA heals, it flattens. Eventually only a puckered scar remains.
KAs pass through three stages each lasting 2 to 3 months. Initially there is a rapid growth phase, followed by a static phase when it remains unchanged and then a phase of involution or healing.
How will a keratoacanthoma be diagnosed?
The most important condition to rule out is one type of skin cancer called a squamous cell carcinoma. The treatment for both is removal, and the specimen will be sent to the laboratory. The two conditions do look similar even under the microscope.
Can it be cured?
Yes, removal leads to cure.
How can a keratoacanthoma be treated?
If left alone, KAs will eventually go away without any treatment. However this can take many months. Active treatment is usually best to confirm the diagnosis.
One method is to scrape the KA off with a sharp spoon-like instrument (a curette) under a local anaesthetic, and then to touch the raw area left behind with a hot point (cautery). The specimen that has been scraped off can then be sent to the laboratory. This method is most suitable for small KAs.
If there is any doubt over the diagnosis, it is best for the bump to be cut out and the area to be closed with stitches. This provides a better specimen for the pathologist to look at.
Occasionally small KAs are dealt with by freezing them with liquid nitrogen.
A few very large ones may be treated with radiotherapy.
If there is any doubt about the diagnosis, follow-up will be arranged.
What can I do?
If you have had a KA, you may be at increased risk of developing a skin cancer later on. You will be taught how to examine your own skin regularly. Avoiding too much exposure to the sun is sensible. You can achieve this by covering yourself up and using sun protection creams. Use a high factor (minimum sun protection factor 30), broad spectrum sunscreen (blocks both types of ultraviolet radiation, UVA and UVB) on areas that you cannot cover.
Where can I get more information about keratoacanthomas?
This is available at the following websites:
www.dermnetnz.org/lesions/keratoacanthoma.html
www.emedicine.com/DERM/topic206.htm
The British Skin Foundation fund vital research into all skin diseases. To find out how you can help, please visit the British Skin Foundation website here.
This leaflet aims to provide accurate information about the subject and is a consensus of the views held by representatives of the British Association of Dermatologists: its contents, however, may occasionally differ from the advice given to you by your doctor.
BRITISH ASSOCIATION OF DERMATOLOGISTS
PATIENT INFORMATION LEAFLET
PRODUCED AUGUST 2005
UPDATED MAY 2010