Keratoacanthomas

ByVinod E. Nambudiri, MD, MBA, EdM, Harvard Medical School
Reviewed/Revised Jan 2024
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Keratoacanthomas are round, firm, usually flesh-colored growths that have a central crater that is scaly or crusted. Some keratoacanthomas may be a form of squamous cell carcinoma.

Keratoacanthomas appear most commonly on sun-exposed areas, such as 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.

Keratoacanthoma
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This round, high, firm bump and a central crater is typical of keratoacanthoma, which is thought to be a form of squamous cell carcinoma.
Image provided by Thomas Habif, MD.

Diagnosis of Keratoacanthomas

  • Biopsy

To confirm the diagnosis of keratoacanthoma, 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.

Treatment of Keratoacanthomas

  • Surgery or injections of methotrexate or 5-fluorouracil

Prevention of Keratoacanthomas

Because keratoacanthomas may be caused by exposure to sun, people can help prevent this cancer by doing the following, starting in early childhood:

  • 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

More Information

The following English-language resource may be useful. Please note that THE MANUAL is not responsible for the content of this resource.

  1. American Cancer Society: What Are Basal and Squamous Cell Skin Cancers? Information about squamous cell carcinoma, including treatment options and prognosis

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