Seborrhoeic keratosis (seborrheic keratosis): causes, removal and when to worry

BAD says SK do not need treatment as they are harmless and cause no symptoms. For those who wish to have them removed, usually in the private sector, options include freezing with liquid nitrogen (cryotherapy), laser, or scraping off (curettage) under local anaesthetic. It adds that individual SK can be treated successfully but can regrow in the same site and others may continue to appear.

BAD states that treatments for SK are not funded by the NHS. NHS Scotland's Right Decisions guidance says that if the diagnosis is certain, reassurance is enough, and that treatment in primary care, where available, can be considered for symptomatic lesions with cryotherapy by a trained nurse or curettage for larger ones, with specimens sent for pathology. Referral to a specialist is only for diagnostic doubt. The PCDS says very thick lesions are best removed by curettage and cautery with samples sent for histology.

None of the UK sources reviewed here describe removing a seborrhoeic keratosis at home. The options the British Association of Dermatologists (BAD) lists are all clinic treatments: freezing with liquid nitrogen, laser, or scraping off under local anaesthetic.

There is also a safety reason to have it looked at first. BAD says a very dark seborrhoeic keratosis can look similar to a melanoma, and that a skin biopsy may be done if there is any doubt. A spot that has been scraped, cut or burned at home cannot then be examined in its original state. If a growth is catching on clothing or bothering you, speak to a GP or pharmacist about options rather than picking at it.

Seborrhoeic keratoses (SK) are also called seborrhoeic warts and basal cell papillomas. BAD describes them as benign growths caused by a build-up of skin cells. The Primary Care Dermatology Society calls an SK a benign overgrowth of epidermal keratinocytes of unknown cause, prevalent in middle-aged and older people.

The name is misleading. BAD stresses they are nothing to do with sebaceous (oil) glands or viral warts. They are also not contagious.

BAD says SK have a rough surface and range from pink to almost black, and look as if stuck onto the skin. The PCDS describes a thickened lesion that is scaly or greasy, sometimes with an irregular warty surface, which sits on top of normal-looking skin and gives the impression that it could be picked off. Most are 1 to 3 cm across, though some are larger.

They occur most often on the trunk, and are also common on the head and neck. Thinner, paler lesions tend to arise on thinner skin such as the lower legs and forearms. On darker skin, BAD says they can appear as many small dark brown or black bumps, particularly on the face and neck, called dermatosis papulosa nigra.

• A waxy, rough or warty surface that looks stuck on.

• Colours from pale yellow or pink to brown and black.

• A single growth or many.

• New ones may appear over the years, and existing ones usually stay.

The cause is unknown. BAD says it has been suggested that sunlight is a risk factor, and that some people may inherit a tendency. The PCDS says they most commonly appear from the fourth decade onwards, although younger adults can be affected, and that some people with a family history have very large numbers.

BAD says SK are harmless and usually cause no symptoms, but they can itch, become red and sore, and catch on clothing. Many people dislike how they look, particularly on the face. The PCDS adds that part or all of a lesion can come away with minimal trauma, and that a lesion is usually non-tender unless it has been traumatised.

BAD says SK are much more common than skin cancers, but a very dark one can look similar to a melanoma. That is why a GP or specialist should check any changing brown or black lesion, and why a skin biopsy may be done if there is doubt. SK can also become a worry if they are red, itchy, sore or bleeding.

The PCDS says that if there is any uncertainty about the diagnosis the person should be referred urgently for teledermoscopy or through the urgent skin cancer pathway. It also describes the Leser-Trélat sign, a sudden eruption of many SK that rapidly grow, and says that when it occurs with weight loss, digestive symptoms or other red flags, urgent investigation is needed.

BAD advises that you always contact your doctor if you are worried about a pigmented spot that is changing in any way. It says a general practitioner or specialist should check any changing brown or black lesion, and that seborrhoeic keratoses can become a worry if they are red, itchy, sore or bleeding.

The Primary Care Dermatology Society says that if there is any uncertainty about the diagnosis, a person should be referred urgently through the skin cancer pathway, and that a sudden eruption of many growths with weight loss or digestive symptoms needs urgent investigation.

On the NHS, a GP can confirm the diagnosis and reassure you. BAD says treatments are not funded by the NHS, while NHS Scotland's Right Decisions guidance describes treatment of symptomatic lesions in primary care, where that service is offered, and referral only if there is diagnostic doubt.

Private dermatology and skin clinics offer freezing, laser and curettage. Ask who will examine the growth first, whether a removed lesion will be sent for laboratory testing, what the total cost is, and be aware that BAD says growths can regrow at the same site.