Keratoacanthomas are round, firm, usually pink or 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, 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 Overview of Skin Cancer Skin cancer is the most common type of cancer. Skin cancer is most common among people who work or play sports outside and among sunbathers. Fair-skinned people are particularly susceptible... read more .

Biopsy

To confirm the diagnosis of keratoacanthoma, doctors often do a biopsy Biopsy Doctors can identify many skin disorders simply by looking at the skin. A full skin examination includes examination of the scalp, nails, and mucous membranes. Sometimes the doctor uses a hand-held... read more , in which a piece of skin is removed and examined under a microscope. Sometimes they completely remove the tumor during the biopsy.

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

Avoiding the sun Avoidance Sunburn results from a brief (acute) overexposure to ultraviolet (UV) light. Overexposure to ultraviolet light causes sunburn. Sunburn causes painful reddened skin and sometimes blisters, fever... read more : 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 Clothing Sunburn results from a brief (acute) overexposure to ultraviolet (UV) light. Overexposure to ultraviolet light causes sunburn. Sunburn causes painful reddened skin and sometimes blisters, fever... read more : For example, long-sleeved shirts, pants, and broad-brimmed hats
Using sunscreen Sunscreens Sunburn results from a brief (acute) overexposure to ultraviolet (UV) light. Overexposure to ultraviolet light causes sunburn. Sunburn causes painful reddened skin and sometimes blisters, fever... read more : 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

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 5-fluorouracil.

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