Keratoacanthoma

A keratoacanthoma is a fast-growing, dome-shaped bump that often has a scab-like plug in the center. It usually appears on skin that gets a lot of sun, like your face, neck, arms or hands. It’s pronounced “ker-a-to-ac-an-tho-ma.”

This tumor is usually noncancerous and often goes away on its own. However, it looks a lot like a type of skin cancer called squamous cell carcinoma. That’s why healthcare providers treat keratoacanthomas like skin cancer to be safe, and some doctors even consider them a type of squamous cell carcinoma skin cancer.

If you notice any new growths or changes on your skin, see a healthcare provider for a check-up.

Types of keratoacanthomas

There are many different types, including:

• Solitary keratoacanthoma: You only have one bump on your skin. This is the most common type.
• Multiple keratoacanthomas (Ferguson-Smith syndrome): Several bumps appear over time, often if you have a biological family history of this condition.
• Subungual keratoacanthoma: A bump forms under or around your fingernail or toenail.
• Mucosal keratoacanthoma: This type appears on moist areas, like inside your mouth or nose.
• Giant keratoacanthoma: The bump grows much larger than usual, sometimes more than 6 inches (15 centimeters) wide.
• Keratoacanthoma centrifugum marginatum: A rare type that grows outward in a ring shape while the center heals and flattens.
• Generalized eruptive keratoacanthoma of Grzybowski: Many small bumps appear all over your body. These may itch or burn, and these often don’t go away on their own.

Keratoacanthoma symptoms

A keratoacanthoma usually starts as a small bump that grows quickly over several weeks. It may stay in a bump shape before slowly shrinking. It often has these features:

• About 1 to 2 centimeters wide
• Dome-shaped with a scab-like center
• Firm to the touch
• Pink or darker than your natural skin tone
• Sometimes itchy or slightly tender

Some people feel pain around the bump, especially as it gets bigger.

Where do symptoms appear?

This bump can form anywhere on your body where you have skin. The most common places are on areas of your body that get sun exposure, including your:

• Arms
• Face
• Hands
• Legs
• Neck

In some cases, this condition may affect your mucosal surfaces. These include your lips and the inside of your mouth and gums. These are less common.

Keratoacanthoma causes

Keratoacanthomas can form when hair follicles in your skin start growing abnormally. There isn’t just one cause. Several things may trigger or contribute to their growth, like:

• Too much sun exposure
• A biological family history or genetics
• A weakened immune system
• Certain viruses
• Contact with certain chemicals
• Skin injuries or scars

In rare cases, keratoacanthomas can be part of inherited conditions that cause bumps to appear more than once.

Risk factors

Anyone can develop a keratoacanthoma. But your risk may be higher if you have:

• Certain genetic changes (p53 or H-Ras genes)
• Frequent sun exposure
• Melanoma and take BRAF inhibitors
• Regular contact with certain chemicals, like tar or industrial substances
• Skin injuries, surgery or trauma in the affected area

Complications of keratoacanthoma

These growths rarely spread. But they may leave a scar after healing or removal. This can happen more often if the bump breaks open or you get an infection.

Try not to scratch, pop or squeeze the area. That can damage your skin and slow healing. If it opens on its own, contact a healthcare provider. They can show you how to care for it safely. Getting treatment early helps your skin heal properly and lowers the chance of future problems.

How doctors diagnose keratoacanthoma

A provider will start by asking about your medical history and examining the bump on your skin. Keratoacanthomas can look a lot like skin cancer. So, they may order tests to confirm the diagnosis and rule out other conditions.

Tests may include:

• Skin biopsy: Your provider may completely remove the tumor from your skin. Then, they’ll send it to a lab to examine it under a microscope.
• Imaging tests: Imaging tests, like an X-ray, MRI or CT scan, are rarely needed. But they may help your provider see how deep the growth goes and check the health of surrounding tissue.

Keratoacanthoma stages

Keratoacanthomas usually go through three stages of growth:

• Proliferation: The tumor grows quickly, usually over six to eight weeks. It may have discoloration, with a raised, dome-like shape.
• Maturation: The growth stops getting bigger and develops a crater-like center filled with a keratin plug. This stage can last for weeks to a few months.
• Involution: The bump slowly shrinks and may flatten out. It often heals on its own, leaving behind a small, thin scar.

Keratoacanthoma treatments

Your healthcare provider will likely recommend removing the bump. The main goals are to make sure all abnormal cells are gone and to prevent the bump from coming back.

Treatment options may include:

• Surgical removal (excision): This is the most common treatment. Your provider cuts out the bump. This often happens during a biopsy that also confirms the diagnosis.
• Scraping and burning (electrodessication and curettage): This treatment is for smaller bumps (under 2 centimeters) on areas like your arms or legs. Your provider may scrape it out and burn the base to destroy any leftover cells.
• Mohs surgery: This treatment is for larger tumors (over 2 centimeters) or those on delicate or visible areas like your face. Your provider removes the tumor layer by layer while keeping as much healthy skin as possible.

If surgery isn’t the best option, your provider may recommend alternative treatments, such as medicated creams, like imiquimod or 5-fluorouracil (5-FU), injections with chemotherapy agents or corticosteroids, freezing the lesion with liquid nitrogen or using a light treatment called photodynamic therapy.

When should I see my healthcare provider?

See a healthcare provider if you notice a new skin growth that appears suddenly or grows quickly. They can check it to make sure everything’s OK. These bumps can sometimes look like skin cancer. Even if it seems minor, it’s best to get it looked at.

If you’ve had this condition before or received treatment, you’ll need regular skin checks with a dermatologist, usually once a year. Let your provider know if you notice any new bumps between visits or if your skin isn’t healing after treatment.

Watch for signs of infection, like:

• A fever
• A wound that won’t heal
• Pus
• Swelling

What can I expect if I have keratoacanthoma?

The outlook is usually very good with treatment. Providers can often remove the bump easily and prevent complications. Once removed, it’s rare for it to grow back in the same spot. But you may develop another one in the future if you have certain risk factors, like frequent sun exposure.

Healing after removal usually takes a couple of weeks. Follow-up care is important no matter which treatment option you choose. It helps ensure your skin heals fully and the bump doesn’t return.

As your skin heals, you may notice a small dip or light scar where the growth was. If the scar bothers you, talk to your provider about ways to care for your skin and help it fade over time.

Is there a cure for keratoacanthoma?

Surgery or the other treatments mentioned are often curative. But in some rare cases, it may come back later on a different part of your skin.

Can keratoacanthomas be prevented?

There’s no way to prevent every case, but you can lower your risk by:

• Getting at least once-yearly skin checks if you’re at higher risk
• Protecting your skin from the sun and avoiding tanning equipment
• Seeing your healthcare provider regularly if you take medications that may raise your risk
• Wearing personal protective equipment when working with chemicals