What is seborrheic keratosis?
A seborrheic keratosis (seb-o-REE-ik ker-uh-TOE-sis) is a common benign skin growth, similar to a mole. Most people will have at least one in their lifetime. They tend to appear in mid-adulthood and their frequency increases with age. They are harmless and don’t require treatment, but you can have them removed if they bother you.
Skin growths like seborrheic keratoses are sometimes also called epidermal tumors. That doesn’t mean they’re cancer, though. Technically, moles and warts are also epidermal tumors. That just means they are clusters of extra cells on the epiderma, the outer layer of the skin. They aren’t considered a risk factor for skin cancer.
What does seborrheic keratosis look like?
Seborrheic keratoses are roundish or oval-shaped patches on the skin with a “stuck on” appearance. They are sometimes described as waxy or scaly. They are raised above the skin and even when they are flat you can feel them with your finger. They are usually brown, but can also be black or tan, and less often, pink, yellow or white. They often appear in numbers.
Seborrheic keratoses are characterized by keratin on the surface — the same fibrous protein that fingernails, hooves, and horns are made of. This causes the textural details that often distinguish the growths. Sometimes it looks like small bubbles or cysts within the growth. Sometimes it looks scabby or wart-like. Sometimes it looks like the ridges and fissures in a brain.
Who gets seborrheic keratosis?
Anyone can get one, but most commonly:
- People who are 50 and older. They usually begin to appear in middle age, and rarely in younger people. About 30% of people have at least one by the age of 40, and about 75% by the age of 70.
- People with a family history of it. About half of all cases of multiple seborrheic keratoses occur in families, suggesting that the tendency to develop many of them may be inherited.
- Lighter-skinned people. Classic seborrheic keratosis as described here appears less frequently in darker-skinned people. However, a variant of seborrheic keratosis called dermatosis papulosa nigra is very common in darker-skinned people, including those of African, Asian and Hispanic descent.
Symptoms and Causes
What triggers seborrheic keratosis?
We don't know exactly why these growths occur, but we can look at the circumstances that often go along with it. The first is age: seborrheic keratoses are especially common in adults over 50, and they tend to multiply as people get older. Some studies suggest that sun exposure may increase their occurrence. They also appear more frequently in families, which suggests that genetics may play a role. They are not viral or bacterial. They don’t spread and they aren’t contagious.
Seborrheic keratoses usually grow slowly and may develop their texture gradually over time. If many seborrheic keratoses erupt suddenly together, it might raise some concern. This unusual occurrence has sometimes been considered a sign of internal cancer. Doctors call it “the sign of Leser Trélat”. The correlation is not yet proven or explained and may only be a coincidence. But your healthcare provider might want to screen you for any other signs of internal cancer.
Do seborrheic keratoses cause symptoms?
They usually don’t, but people sometimes report:
- Irritation from friction.
If these symptoms annoy you, you may want to have the growth removed.
Diagnosis and Tests
How do you tell seborrheic keratosis from actinic keratosis?
Seborrheic keratosis and actinic keratosis can resemble each other. They both begin to appear after the age of 40, and they both can appear crusty and scaly. It’s important to know the difference because actinic keratosis is more serious than seborrheic keratosis. Unlike seborrheic keratosis, actinic keratosis is caused by sun exposure, and it carries a small risk of turning into skin cancer (5% -10%).
Actinic keratoses vary in color, but they tend to be less pigmented than seborrheic keratoses. They can be flat or slightly raised, but tend to be flatter, and you might feel them before you see them. They feel scaly and rough, but may become more bumpy and wart-like over time, like seborrheic keratoses. They may also itch and bleed. They tend to appear in clusters in frequently sun-exposed areas.
How do you tell seborrheic keratosis from melanoma?
Seborrheic keratosis doesn't turn into melanoma, but the two can be mistaken for each other. Both can be brown or black and appear anywhere on the body. There are some important differences, however:
- Seborrheic keratoses often appear in numbers, while melanoma is usually single.
- Seborrheic keratoses tend to have texture, while melanoma tends to be smooth.
- Seborrheic keratoses are well-defined, while melanoma can have a ragged or blurry border.
- Seborrheic keratoses are uniform, while melanoma may be asymmetrical or have more than one color.
- Seborrheic keratoses change little and slowly, while melanoma can grow and change quickly.
How is seborrheic keratosis diagnosed?
- Examination. Dermatologists can usually identify a seborrheic keratosis with the naked eye.
- Dermoscopy. If in doubt, your healthcare provider may look at the growth under a dermascope, a small, handheld lighted microscope.
- Biopsy.** **If your healthcare provider suspects any cancer, they will want to take a sample — or remove the whole growth — to examine in a lab.
Management and Treatment
How is seborrheic keratosis treated?
You should always have new skin growths clinically diagnosed to make sure they aren’t cancerous. Different kinds of skin growths can be hard to tell apart from each other. If your healthcare provider is in any doubt about your growth, they might want to remove it for biopsy.
If it is clearly a seborrheic keratosis, it won’t require any treatment. But you might want to have it removed if it becomes itchy or irritated or you don’t like the look of it. Your healthcare provider can remove it for you in the office using one of several common methods.
How is seborrheic keratosis removed?
Medical offices offer several options for removing your seborrheic keratosis:
- Cryotherapy. Your healthcare provider will numb the skin and then use liquid nitrogen to freeze the growth. This will cause it to fall off within a few days or weeks. Cryotherapy is a common choice when the diagnosis is clear and there is no need to preserve a sample of the growth for biopsy. One possible side effect is that the skin where the growth was will lose some of its pigment and look lighter.
- Electrodessication/Curettage. Your healthcare provider will numb the skin and then use a targeted electrocurrent to burn the seborrheic keratosis. They use a surgical instrument called a curette to scrape away the remains of the growth. Electrodessication and curettage are also sometimes used individually. The risk of scarring is generally low with both methods, but there is some wound care involved afterward.
- Shave Excision. This is the preferred method when your healthcare provider wants to preserve a sample of the growth to analyze in the lab. After numbing the skin, your healthcare provider will carefully shave off the growth and smooth the skin underneath with a surgical curette. Then they’ll send the shaved growth to the lab for analysis.
- Laser Therapy. Lasers offer an alternative to surgery by burning the growth, sterilizing the wound and sealing the tissue all at once. Laser therapy is quick, but the wound will be sore for a while afterward. Lasers are associated with good cosmetic results.
- Prescription Hydrogen Peroxide. The FDA has recently approved a topical solution of 40% hydrogen peroxide to treat seborrheic keratosis. (Over-the-counter hydrogen peroxide is a 1% solution.) The solution comes in an applicator pen, which your healthcare provider will apply to your seborrheic keratosis several times in one visit. You may need more than one visit to see results. Mild skin reactions are a common side effect.
Is there an over-the-counter treatment for seborrheic keratosis?
Some over-the-counter topical treatments have shown promise for reducing seborrheic keratoses. Research is limited on these solutions. They take time and persistence to work and are not 100% effective. But they also have fewer side effects and little-to-no recovery time. They might be a practical option to try if you want to treat many growths at once. Options include:
- Tazarotene cream 0.1%.
- Alpha Hydroxy Acid (AHA) products, including glycolic acid and salicylic acid peels.
- Vitamin D3 cream.
Outlook / Prognosis
What can I expect if I have seborrheic keratoses?
They may continue to grow at a slow pace. You may continue to grow new ones. They occasionally, but rarely, recede.
What can I expect if I’ve had my seborrheic keratosis removed?
A seborrheic keratosis that has been removed will not return. But you might grow a new one somewhere else.
When should I see my healthcare provider about my seborrheic keratosis?
For the most part, you don’t have to worry about your seborrheic keratosis. However, you should see your healthcare provider if you notice:
- You have a new, unidentified growth.
- It’s itching, irritated or bleeding.
- An old seborrheic keratosis changed its appearance.
- Many growths suddenly develop in a short period.
A note from Cleveland Clinic
Seborrheic keratosis is nothing to worry about, but you should have it diagnosed just to make sure it isn’t something else that could be more harmful. If you want to have it removed, there are a number of options available. Your healthcare provider can walk you through the pros and cons of each method and help you determine the best one for you, based on the nature and location of the growth. Seborrheic keratoses that are removed will not return, but you might get a new one somewhere else.
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