Seborrheic keratosis

Published on 18/03/2015 by admin

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Last modified 18/03/2015

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Seborrheic keratosis

Richard J. Motley

Evidence Levels:  A Double-blind study  B Clinical trial ≥ 20 subjects  C Clinical trial < 20 subjects  D Series ≥ 5 subjects  E Anecdotal case reports

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Seborrheic keratosis is a benign, exophytic, warty, lightly pigmented growth of the skin surface that becomes increasingly common with age. Found mainly on the trunk, often at sites of pressure, it is a cosmetic nuisance and rarely a cause for diagnostic confusion. Several variants exist and are described below.

Management strategy

Many patients present with seborrheic keratoses because of concern about possible melanoma, and reassurance may be all that is required. Occasionally the lesion can become ‘irritated’ and show erythema, crusting, and itching (lower lesion in photograph). In this case the appearance may resemble a pyogenic granuloma or squamous cell carcinoma.

Where treatment is requested there are several options and the choice will depend on patient and physician preference. Surgical excision, although effective, is never the treatment of choice and usually indicates that the physician failed to make the correct clinical diagnosis or is unfamiliar with alternative treatments. When the diagnosis is in doubt then material should be taken for histologic examination, preferably by a ‘shave’ or tangential biopsy technique or by sharp curettage. Blunt curettage provides poor material for histologic assessment. Cautery is very effective at softening the lesion and often allows it to be removed with minimal effort, the heat separating the lesion at the dermoepidermal junction. The ‘melting’ of the lesion observed after the application of heat is almost diagnostic. Smaller lesions can be ‘flicked off’ the skin using a traditional curette, often without local anesthesia. Heat can be applied to the surface of the lesion followed by curettage, and for superficial lesions ‘curettage’ can be achieved using a cotton gauze swab to wipe away the softened lesion. Cautery can also be used after shave excision to treat any tissue remnants. With all these treatments the aim is to remove the lesion, but little of the underlying skin surface.

Cryotherapy using a liquid nitrogen spray is an alternative method of treatment. Liquid nitrogen is sprayed onto the lesion until it is frozen, and then continued for 5 to 10 seconds. It can be undertaken without local anesthesia because freezing reduces sensation of pain, and this can be an advantage when treating multiple lesions. After a day or two the treated lesion blisters and crumbles away. The underlying wound heals over after several days and is often quite exudative, requiring daily cleansing by the patient. Overall the recovery period is longer and the wound slower to heal than following curettage and cautery. Whereas following cautery hyperpigmentation is common, following cryotherapy, hypopigmentation occurs. For this reason it is not recommended in black people.

Seborrheic keratosis variants

Senile or ‘solar’ lentigines can be considered to be flat versions of the seborrheic keratosis. Sometimes referred to as ‘age’ or ‘liver’ spots, these small pigmented papules and plaques are more commonly seen on areas of frequent sun exposure, such as the face and dorsa of the hands. Their true nature can be recognized by the slight velvety texture to the lesional surface, which is best seen with tangential lighting. This indicates that the lesion is not a true lentigo but a superficial keratosis. These lesions are amenable to very minor treatments. Topical tretinoin cream can be effective. Other treatments include light abrasion with an exfoliating cream, light dermabrasion or laser resurfacing, cryotherapy, or chemical peels using trichloroacetic acid or phenol. A favorite treatment is minimal cautery followed by ‘curettage’ with a cotton gauze swab. This leaves an erythematous superficial wound that heals rapidly.

Dermatosis papulosa nigra is commonly seen on the cheeks of black adults. These small seborrheic warts are easily treated by light cautery or diathermy followed by cotton gauze curettage, but patients should be warned about the possibility of hyperpigmentation.

Stucco keratoses are small grayish-white seborrheic keratoses which are typically found on the forearms and lower legs and are easily removed with curettage without bleeding. The edge of these lesions is often curled up away from the skin surface.

Giant seborrheic keratoses are large lesions, usually found on the scalp, and are often several centimeters in diameter.

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