(See also Overview of Skin Cancer.)
Keratoacanthomas appear most commonly on sun-exposed areas, the face, forearms, and back of the hands and grow quickly. In 1 or 2 months, they typically grow into lumps about 1 inch (about 2.5 centimeters) wide, but sometimes they grow over twice as large. They may spontaneously disappear within a few months, often leaving a scar.
The cause of keratoacanthomas is unknown. Most doctors consider keratoacanthomas to be a form of squamous cell carcinoma, a type of skin cancer.
Diagnosis
Because a keratoacanthoma might be cancerous, doctors often do a biopsy, in which a piece of skin is removed and examined under a microscope. Sometimes they completely remove the tumor during the biopsy.
Prevention
Because keratoacanthomas can be caused by exposure to sun, people can help prevent this cancer by doing the following:
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Avoiding the sun: For example, seeking shade, minimizing outdoor activities between 10 AM and 4 PM (when the sun’s rays are strongest), and avoiding sunbathing and the use of tanning beds
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Wearing protective clothing: For example, long-sleeved shirts, pants, and broad-brimmed hats
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Using sunscreen: At least sun protection factor (SPF) 30 with UVA and UVB protection used as directed and reapplied every 2 hours and after swimming or sweating but not used to prolong sun exposure
