Seborrheic Keratosis

What a seborrheic keratosis looks like

Seborrheic keratoses are easy to recognize once you know their features:

• Stuck-on look: they appear pasted onto the skin surface, as if you could pick them off.
• Waxy or warty surface: rough, slightly greasy and crumbly, sometimes with visible small pits or white dots (horn cysts).
• Color: light tan, brown or black. One person can have spots of many shades.
• Shape: round or oval with a sharp edge, flat or raised.
• Size: from a few millimeters to more than 2.5 cm (1 inch).
• Location: the chest, back, belly, face, scalp and neck are most common. They never appear on the palms or soles.

People often have many. They are sometimes mistaken for warts, but they are not caused by a virus and are not contagious.

Variants

• Dermatosis papulosa nigra: many small dark bumps on the cheeks and around the eyes, common in people with darker skin.
• Stucco keratoses: small, gray-white rough spots on the lower legs and feet of older adults.
• Irritated seborrheic keratosis: red, swollen, crusted or bleeding after friction or scratching.

Symptoms

Most seborrheic keratoses cause no symptoms at all. Some:

• itch, especially in dry skin or in winter
• catch on clothing, bra straps, belts or jewelry
• become red, sore and crusted when irritated
• bleed after being scratched or rubbed

Is pain a symptom of seborrheic keratosis?

Not usually. A seborrheic keratosis is not painful by itself. It can become tender if it is irritated, inflamed, scratched or partly torn off. Spontaneous pain, bleeding without injury, or a sore that will not heal is not typical, and the spot should be examined to rule out skin cancer.

Causes and risk factors

The exact cause is unknown. What is known:

• Age: the main risk factor. They are uncommon before 30 and very common over 50.
• Genes: they often run in families, and specific gene changes have been found in the growths.
• Sun exposure: may play a role, since they are common on sun-exposed skin, but they also occur on covered areas.
• Hormonal changes: they can appear or increase during pregnancy.

They are not caused by poor hygiene, and they do not spread from person to person.

Seborrheic keratosis vs melanoma and other spots

Most seborrheic keratoses are obvious, but some dark or irregular ones look like melanoma, and the reverse is also true. A dermatologist checks with a magnifying light called a dermatoscope, which shows features specific to each.

Other look-alikes:

• Actinic keratosis: rough, scaly, pink or red patches on sun-damaged skin. These are precancerous and are treated.
• Age spots (solar lentigines): flat, brown spots on sun-exposed skin. Not raised or waxy.
• Skin tags: soft, skin-colored flaps on a narrow stalk, usually in skin folds.
• Pigmented basal cell carcinoma: a pearly or shiny bump that may bleed and fail to heal.

Sign of Leser-Trelat

Very rarely, a sudden appearance of dozens of seborrheic keratoses over a short time, often with itching, can be a sign of an internal cancer, usually of the stomach or bowel. This is uncommon, but a sudden eruption is worth mentioning to your doctor.

Diagnosis

A dermatologist usually diagnoses seborrheic keratosis just by looking, often with a dermatoscope. If there is any doubt, they remove part or all of the growth (a biopsy) and send it to a lab. Spots that are removed for cosmetic reasons are not always sent for testing, so tell your doctor if a spot has changed.

Treatment and removal

Seborrheic keratoses do not need treatment. Removal is considered when a growth is irritated, itchy or bleeding, catches on clothing, is unsightly, or the diagnosis is uncertain. Insurance often does not cover purely cosmetic removal.

Options include:

• Cryotherapy: freezing with liquid nitrogen. The spot blisters and falls off within weeks. It can leave a lighter patch, especially on darker skin.
• Curettage: scraping off the growth after numbing the skin, sometimes with electrocautery to stop bleeding.
• Electrodesiccation: burning off the growth with an electric current.
• Shave excision: used when tissue is needed for testing.
• Laser treatment for some, especially small facial growths.
• Topical hydrogen peroxide 40% solution has been approved in the US for raised seborrheic keratoses, though availability varies.

Do not try to cut, scrape or pick off a growth at home. This causes bleeding, infection and scarring, and could mean a skin cancer is missed.

Outlook

Seborrheic keratoses are harmless and do not turn into cancer. Treated spots usually do not return, but new ones commonly appear over time. Itchy, dry skin can be soothed with a fragrance-free moisturizer. Keep an eye on all your spots and show a doctor any that change, look different from the others, or bleed without injury.

Frequently asked questions

What are wisdom spots in dermatology?

"Wisdom spots" is an informal, friendly name for seborrheic keratoses, the waxy brown stuck-on growths that become common with age. Dermatologists sometimes use it to reassure patients that the spots are a normal, harmless sign of getting older, like gray hair.

Can seborrheic keratosis turn into cancer?

No. Seborrheic keratoses are benign and do not become cancer. However, a skin cancer can occasionally look similar, or grow next to one. Any spot that changes quickly, looks different from the rest, or bleeds without injury should be checked.

Why do seborrheic keratoses itch?

They can itch when the skin is dry, when clothing rubs them, or when they become inflamed. Moisturizing and avoiding scratching usually help. A doctor can freeze or remove a persistently itchy growth.

How can I get rid of seborrheic keratosis?

A doctor can remove them by freezing with liquid nitrogen, scraping (curettage), electrocautery or laser. There is no proven home remedy, and picking or cutting them off risks infection, scarring and missing a skin cancer.

Are seborrheic keratoses contagious?

No. They are not caused by a virus, unlike true warts, and cannot spread from person to person or from one part of your body to another.