Risk factors for the development of keratoacanthoma include:
- Age over 50
- Fair skin, light hair, or light eyes
- Chronic exposure to sunlight or other ultraviolet light
- Exposure to certain chemicals, such as tar
- Exposure to radiation, such as X-ray treatment for internal cancers
- Long-term suppression of the immune system, such as organ transplant recipients
- Long-term presence of scars, such as from a gasoline burn
- Chronic ulcers
- Presence of particular strains of the wart virus (human papillomavirus)
- Previous skin cancer
- Center of the face
- Backs of hands
- Lower legs, especially in women
In rare cases, multiple keratoacanthomas may develop as part of a larger group of symptoms (syndrome).
Most keratoacanthoma are painless, though some may be itchy. Depending on the site of involvement, keratoacanthoma may interfere with normal function of the affected area.
- Avoid ultraviolet (UV) light exposure from natural sunlight or from artificial tanning devices.
- Wear broad-spectrum sunscreens (blocking both UVA and UVB) with SPF 30 or higher, reapplying frequently.
- Wear wide-brimmed hats and long-sleeved shirts.
- Stay out of the sun in the middle of the day (between 10:00 AM and 3:00 PM).
Try to remember to tell your doctor when you first noticed the lesion and what symptoms, if any, it has. Also, young adults should ask adult family members whether or not they have ever had a skin cancer and relay this information to their physician.
If your physician suspects a keratoacanthoma, he or she will first want to establish the correct diagnosis by performing a biopsy. The procedure involves:
- Numbing the skin with an injectable anesthetic.
- Sampling a small piece of skin by using a flexible razor blade, a scalpel, or a tiny cookie cutter (called a "punch biopsy"). If a punch biopsy is taken, a stitch (suture) or 2 may be placed and will need to be removed 6–14 days later.
- Having the skin sample examined under the microscope by a specially trained physician (dermatopathologist).
- Freezing with liquid nitrogen (cryosurgery), in which very cold liquid nitrogen is sprayed on the keratoacanthoma, freezing it and destroying it in the process.
- Electrodesiccation and curettage, also known as "scrape and burn." After numbing the lesion, the doctor uses a sharp instrument (curette) to "scrape" the skin cancer cells away, followed by an electric needle to "burn" (cauterize) the tissue. The electrodesiccation helps to kill the cancer cells and also to stop any bleeding at the site.
- Removal (excision), in which the doctor uses a knife-like instrument (scalpel) to cut out the keratoacanthoma and then place stitches to bring the wound edges together.
- Mohs micrographic surgery, in which the physician takes tiny slivers of skin from the cancer site until it is completely removed. This technique is particularly useful for keratoacanthoma located on the nose, the ears, the lips, and the hands.
- Radiation treatment, where X-ray therapy is often useful for patients who might have difficulty with a surgical procedure because of other health issues.
Finally, it is important to remember that treatment of keratoacanthoma is not complete once the skin cancer has been removed. Frequent follow-up appointments with a dermatologist or with a physician trained to examine the skin are essential to ensure that the keratoacanthoma has not returned and that a new skin cancer has not developed somewhere else on your body. In addition, good sun protection habits (see the above Self-Care section) are vital to preventing further damage from UV light.