Keratoacanthoma is a benign skin tumor that looks similar to squamous cell carcinoma, a type of skin cancer. Here are five things you need to know about it.

What are the signs of keratoacanthoma?

Keratoacanthomas are smooth and dome-shaped and usually appear on parts of the skin that get a lot of sun exposure like the face, arms, or hands. These tumors are very small at first and may be only one or two millimeters in diameter when they first appear. Over the period of a few weeks, they can grow to one to three centimeters. Any fast-growing skin growths should be cause for alarm and immediate medical attention, so if you notice this growth, see your doctor.

What are the risk factors?

This condition tends to affect people who have had a lot of sun exposure in the past. If you spend a lot of time outdoors without sun protection, you may be at risk of developing this condition. Another risk factor is previous injury. Keratoacanthomas tend to form on the sites of old injuries or traumas.

How serious is it?

These tumors are benign, meaning that they're not cancerous. However, keratoacanthomas can look similar to more serious skin conditions like squamous cell carcinoma, so your doctor may want to take a biopsy of the tumor to make sure that it's not anything serious.

How is it treated?

Even though keratoacanthomas aren't serious, surgical removal is generally recommended because of their similarity to squamous cell carcinoma. Your doctor will refer you to an oncologist, a doctor that specializes in treating tumors, to perform surgical excision to remove the tumor. This simple surgery involves cutting away the tumor with a scalpel. A margin of healthy tissue from around the tumor will also be removed to make sure that no tumor cells are left behind.

If you're scared to have surgery, or your doctor doesn't think you're a good candidate for it, other treatments are available. Oral retinoids can be given to treat the tumor. Some people have been successfully treated with imiquimod cream, a medication typically to treat genital warts.

Is keratoacanthoma common?

Keratoacanthoma is a fairly common condition among light-skinned people, and it's uncommon in people with darker skin. A study of white Americans in Hawaii found that it affects 106 people per 100,000. It can affect people of any age, but it's rare in people younger than 20 and tends to occur in people who are in their seventies or older. The condition is much more common among men: men are twice as likely to have the condition.

If you notice a fast-growing tumor on your skin, make sure to see your doctor immediately.