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Keratoacanthomas ˌker-ət-ō-ˌak-ˌan-ˈthō-mə

By Gregory L. Wells, MD, Staff Dermatologist, Ada West Dermatology, St. Luke’s Boise Medical Center, and St. Alphonsus Regional Medical Center

Keratoacanthomas are round, firm, usually pink or flesh-colored growths that have a central crater that is scaly or crusted, and some keratoacanthomas may be a form of squamous cell carcinoma.

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 can grow into lumps up to 1 inch (about 2.5 centimeters) wide. They may spontaneously disappear within a few months, often leaving a scar.

The cause is unknown. Most doctors consider keratoacanthomas to be a form of squamous cell carcinoma, a type of skin cancer.

Diagnosis of Keratoacanthomas

  • Biopsy

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 of Keratoacanthomas

Because keratoacanthomas can be caused by exposure to sun, people can help prevent this cancer by doing the following:

  • 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

  • Wearing protective clothing: For example, long-sleeved shirts, pants, and broad-brimmed hats

  • 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

Treatment of Keratoacanthomas

  • Surgery or injections of methotrexate or 5-fluorouracil

There is no guarantee that a keratoacanthoma will spontaneously disappear, and even when they do disappear, there is often a scar. Thus, keratoacanthomas are usually cut out or scraped (curetted) or injected with methotrexate or fluorouracil.

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