Seborrheic keratosis (seb-o-REE-ik care-uh-TOE-sis) is a common skin growth. It may look worrisome, but it is benign (not cancer). These growths often appear in middle-aged and older adults. Some people get just one. It is, however, more common to have many. They are not contagious.
Most often seborrheic keratoses start as small, rough bumps. Then slowly they thicken and get a warty surface. They range in color from white to black. Most are tan or brown.
They can appear almost anywhere on the skin.
Seborrheic keratoses can look like warts, moles, actinic keratoses, and skin cancer. They differ, though, from these other skin growths. Seborrheic keratoses have a waxy, “pasted-on-the-skin” look. Some look like a dab of warm, brown candle wax on the skin. Others may resemble a barnacle sticking to a ship.
Seborrheic keratoses: Signs and symptoms
Seborrheic keratoses tend to:
- Start as small, rough bumps, then slowly thicken and develop a warty surface.
- Have a waxy, stuck-on-the-skin look.
- Be brown, though they range in color from white to black.
- Range in size from a fraction of an inch to larger than a half-dollar.
- Form on the chest, back, stomach, scalp, face, neck, or other parts of the body (but not on the palms and soles).
- Cause no pain — some itch.
Seborrheic keratoses: Who gets and causes
Who gets seborrheic keratoses?
In most people, seborrheic keratoses first appear in middle age or later. People who are most likely to get these growths have family members with seborrheic keratoses.
Sometimes the growths appear during pregnancy or after estrogen replacement therapy. Children rarely have these growths.
What causes seborrheic keratoses?
The cause of seborrheic keratoses is unknown. We do know the following:
- Seborrheic keratoses seem to run in families. Some people seem to inherit a tendency to get many of these growths.
- Some studies suggest that sun exposure may play a role. But we know that these growths appear on skin that gets sun and skin that is always covered. So more research is needed.
- Seborrheic keratoses are not contagious. These growths may seem to multiply and spread to other parts of the body. The truth is, this does not happen.
Seborrheic keratoses: Diagnosis, treatment, and outcome
How do dermatologists diagnose seborrheic keratoses?
In most cases, a dermatologist can tell if your skin growth is a seborrheic keratosis by looking at it. Sometimes a seborrheic keratosis can look like a skin cancer. If it does, the dermatologist will remove the growth so that it can be looked at under a microscope. This is the only way to tell for sure whether a growth is skin cancer.
How do dermatologists treat seborrheic keratoses?
Because seborrheic keratoses are harmless, they most often do not need treatment. A dermatologist may remove a seborrheic keratosis when it is:
- Hard to distinguish from skin cancer.
- Large or gets easily irritated when clothes or jewelry rub against it.
- Unsightly to a patient.
If your dermatologist does a biopsy, the doctor will likely shave off the growth with a scalpel or scrape it off.
Treatments for seborrheic keratoses include:
- Cryosurgery: The dermatologist applies liquid nitrogen, a very cold liquid, to the growth with a cotton swab or spray gun. This freezes the growth. The seborrheic keratosis tends to fall off within days. Sometimes a blister forms under the seborrheic keratosis and dries into a scab-like crust. The crust will fall off.
- Electrosurgery and curettage: Electrosurgery (electrocautery) involves numbing the growth with an anesthetic and using an electric current to cauterize (burn) the growth. A scoop-shaped surgical instrument, a curette, is used to scrape off the treated growth. This is the curettage. The patient does not need stitches. There may be a small amount of bleeding. Sometimes the patient needs only electrosurgery or just curettage.
After removal of a seborrheic keratosis, the skin may be lighter than the surrounding skin. This usually fades with time. Sometimes it is permanent. Most removed seborrheic keratoses do not return. But a new one may occur elsewhere.
Seborrheic keratoses: Tips for managing
Most seborrheic keratoses do not require care. You should see a dermatologist if:
- The growth grows quickly, turns black, itches, or bleeds (possible signs of skin cancer).
- Many new skin growths suddenly appear. This can be a sign of cancer inside the body.
- Your skin growth does not look like a typical seborrheic keratosis.
- Your growth is dry, flat, rough, and scaly. It could be an actinic keratosis, which can progress to a type of skin cancer.
- The growth is easily irritated, such as from shaving or clothes rubbing against it.
- You want the growth taken off because you do not like how it looks.
Do not try to remove a seborrheic keratosis yourself. There is a risk of infection.