Seborrhoeic keratoses

Seborrhoeic keratoses are one of the most common spots or lumps on the skin. Because they often develop on previously normal skin and appear different from other spots on the body, they frequently cause concern. Fortunately, they are harmless and treatment is rarely required.

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How common are seborrhoeic keratoses?

Almost every Australian over 50 has at least one seborrhoeic keratosis. With increasing age, more seborrhoeic keratoses appear. It’s common for people over 75 to have dozens. Although seborrhoeic keratoses are especially common in older people, about a quarter of young adults (aged 15-30) have them.

Seborrhoeic keratoses can appear on most parts of the skin (but rarely on the palms, soles or genitals). They are more likely to appear on areas that have been exposed to sunlight, but they don’t always appear on these areas.

Seborrhoeic keratoses tend to be more common in people whose parents or grandparents have many.

There is no known way of preventing them from appearing.

Appearance

The appearance of seborrhoeic keratoses varies widely.

A typical seborrhoeic keratosis is slightly raised and has a “stuck-on” appearance. The edges are usually clearly defined, and it’s possible to pick at them.  They may be very dry, rough and crusty, or smooth and waxy in consistency.

The colour is usually darker than the surrounding skin, but can be black, dark brown, grey, yellow, white, or skin-coloured.

Diagnosis

Usually a doctor can diagnose a seborrhoeic keratosis by looking at it and feeling its consistency. High magnification examination with a dermoscope usually shows characteristic features.

Sometimes seborrhoeic keratoses don’t exactly fit these criteria, and even an experienced doctor might find them challenging to identify.

In some cases, they can look like skin cancers (melanoma or squamous cell carcinoma) — and a small number of melanomas look like seborrhoeic keratoses and can potentially be missed.

If there is any doubt about the diagnosis, the spot should be biopsied. This is commonly done by shaving it off the surface of the skin. The specimen can then be examined by a skin pathologist to provide a diagnosis.

If you have a single or small number of suspect spots, they can be examined by our doctor during a mole check appointment.

Complications

Seborrhoeic keratoses have no dangerous complications, but people often don’t like them because:

• occasionally they are very itchy
• they may be unsightly
• they may become irritated or caught in clothing

Some people think of them as a reminder of ageing, even though they are also common in young people.

The main medical concern is that in people with many seborrhoeic keratoses, it could be difficult to identify a new or changing melanoma or other skin cancer in a region surrounded by many other dark or raised spots.

Treatments

Because seborrhoeic keratoses are harmless, it’s not medically necessary to treat them. They are usually treated for cosmetic reasons or because they are itchy or irritated.

Unfortunately, seborrhoeic keratoses frequently return after treatment.

Exfoliation

After soaking the seborrhoeic keratosis (in a bath or swimming), gently rub it with a rough object such as an exfoliating glove, pumice stone, emery board or even fine sandpaper. This treatment may need to be repeated several times, but tends to give a good cosmetic result.

Salicylic or lactic acid

Salicylic and lactic acid preparations dissolve rough, dry and crusted skin, and can be helpful in breaking down seborrhoeic keratoses. They are available over the counter or online without a prescription. Stronger concentrations of salicylic acid are more effective against seborrhoeic keratoses, but can lead to pigmentation abnormalities in the treated area.

Cryotherapy (freezing)

A doctor can freeze off seborrhoeic keratoses on the spot during a consultation. This treatment is popular because it usually only needs to be performed once. Disadvantages of this treatment include pain, blistering and redness at the treated site, and a small risk of scarring.

There is no Medicare rebate for this treatment, so there may be an out of pocket expense.

Shave or excision

If the diagnosis of a seborrhoeic keratosis is not obvious, a doctor can shave it off the surface of the skin or cut around it to remove it. This is best way to confirm the diagnosis and rule out skin cancer in uncertain cases.

Electrosurgery and radiofrequency surgery

Seborrhoeic keratoses can be removed by burning them off. Radiofrequency surgery is often recommended if a good cosmetic result is required, for example if the seborrhoeic keratosis is on the face or upper chest. This technique tends to leave less scarring than other methods.

Broadband light / IPL

If a seborrhoeic keratosis is very flat and pigmented, treatment with broadband intense pulsed light can sometimes be successful. This treatment can be useful if:

• the skin is sun-damaged and there are lentigines (freckles) and/or prominent blood vessels or angiomas, which can be treated at the same time
• there are many seborrhoeic keratoses and a good cosmetic outcome with minimal scarring is desired.

Hydrogen peroxide

Concentrated hydrogen peroxide is an effective treatment for seborrhoeic keratoses. It is a powerful bleach and must therefore be used with extreme caution.

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