What is a seborrheic keratosis?

A seborrheic keratosis is a noncancerous (benign) growth on the skin. Its color can range from white, tan, brown, or black. Most are raised and appear "stuck on" to the skin. They may look like warts.

Seborrheic keratoses often appear on a person’s chest, arms, back, or other areas. They’re very common in people older than age 50, but younger adults can get them as well. With age, more and more people get one or more of these growths. 

The outer layer of your skin is the epidermis. Cells called keratinocytes make up much of this layer. These cells regularly flake off as younger cells replace them. Sometimes they grow in greater numbers than usual. This can lead to a keratosis. You may have just one or hundreds of these growths. In most cases, these growths only cause cosmetic problems. In some cases, they can cause skin irritation if they’re in a spot that clothes rub.

Seborrheic keratoses are not cancer. But they can sometimes look like growths that are cancer. Because of this, your healthcare provider may need to take a biopsy sample and examine it.

What causes seborrheic keratoses?

It’s not clear what exactly causes seborrheic keratoses. They tend to run in families, so genes may be a factor. Normal skin aging plays a role because the growths are more common with age. Too much sun exposure may also play a role. They are not contagious. You can’t get them from somebody else or spread them to others.

Rarely, many seborrheic keratoses may suddenly appear. This is unusual. It may be a sign of a cancer not linked to the skin, such as colon cancer or lung cancer. If you’ve had many of these growths suddenly appear, tell your healthcare provider. They may want to make sure that you don’t have any type of cancer.

What are the symptoms of seborrheic keratoses?

The growths can:

• Be slightly raised from the surrounding skin

• Be white or light tan in appearance, which may darken to brown or black

• Have a waxy, pasted-on look

• Look scaly or like a wart

• Be well-defined from the surrounding skin

• Not usually cause pain but may sometimes itch a little

They occur most often on the chest, belly, back, neck, arms, face, or other areas that are exposed to sun. You might have only one or up to hundreds of these growths. People tend to develop more of these growths as they age.

How are seborrheic keratoses diagnosed?

A healthcare provider can often diagnose seborrheic keratoses based on how they look. In some cases, a biopsy may be needed.

If you have a skin growth that concerns you, it is always a good idea to see your healthcare provider. Your healthcare provider will ask you about your medical history and symptoms. Your healthcare provider will also give you a physical exam and closely examine the growth.

It’s important for your healthcare provider to make sure any growths are not cancer or precancer. Some signs that may concern your healthcare provider are if the growth:

• Looks smooth on the skin, instead of raised and well-defined

• Has blurred borders

• Is not the same shape on both sides (asymmetry)

• Has dilated blood vessels around it

• Has an open sore in it

• Grew out of a previous mole

If your healthcare provider wants to check for cancer, you will have a skin biopsy. Your healthcare provider will take a tissue sample of the growth or remove the entire growth. It will then be examined under a microscope at a lab to determine if there is cancer.

How are seborrheic keratoses treated?

Seborrheic keratoses usually only cause cosmetic issues. But many people worry about the possibility of cancer. People may also want them removed because they don’t like how they look.

In most cases, they don’t need any treatment. You can choose to remove one or more of them if they get irritated due to clothing, feel itchy, are worried about cancer, or don’t like how they look. They can be removed with:

• Liquid nitrogen. This is called cryotherapy. It freezes the growth, causing it to fall off within days.

• Minor surgery. This can be done in two ways:

  • With a scalpel and a numbing medicine to prevent pain

  • With electricity to burn the growth away and a numbing medicine to prevent pain

Most growths that are removed don’t grow back, but they may occur elsewhere. If they do grow back after treatment, a tissue sample (biopsy) is needed to make sure that the diagnosis was correct and that the growth is not cancer.

Don’t try to remove a seborrheic keratosis yourself. You may be wrong about the diagnosis. The growth may be something more serious. Removing the lesion at home may also cause an infection.

When should I call my healthcare provider?

See your healthcare provider soon if you have:

• A new skin growth

• A growth that’s not the same shape on both sides

• A mole that’s getting larger

• New itching of an old mole

• A mole with a blurred border

• A known seborrheic keratosis that changes in appearance

Key points about seborrheic keratosis

• Seborrheic keratosis is a benign growth on your skin. The growths are not cancer. Usually these growths only cause cosmetic problems. They are very common in older people.

• These growths are dark colored and raised, with a waxy, warty look.

• Your healthcare provider can often diagnose a seborrheic keratosis with a physical exam.

• If your healthcare provider thinks the growth might be cancer, you may need a skin biopsy.

• Most seborrheic keratoses don’t need treatment. You can have them removed if they cause problems or you don’t like how they look.

Next steps

Tips to help you get the most from a visit to your healthcare provider:

• Know the reason for your visit and what you want to happen.

• Before your visit, write down questions you want answered.

• Bring someone with you to help you ask questions and remember what your provider tells you.

• At the visit, write down the name of a new diagnosis and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you.

• Know why a new medicine or treatment is prescribed and how it will help you. Also know what the side effects are.

• Ask if your condition can be treated in other ways.

• Know why a test or procedure is recommended and what the results could mean.

• Know what to expect if you do not take the medicine or have the test or procedure.

• If you have a follow-up appointment, write down the date, time, and purpose for that visit.

• Know how you can contact your healthcare provider if you have questions, especially after office hours and on weekends and holidays.