Diagnosis: Seborrheic keratosis

The lesion was a seborrheic keratosis (SK). Also referred to as senile warts, senile keratoses, seborrheic verrucae, and basal cell papillomas, SKs are common, benign epithelial tumors that usually appear after three decades of life. Most people will develop several such lesions during their lifetime; some will acquire hundreds of them. They are seen on any part of the body except the mucous membranes.

SKs begin as flat, sharply demarcated, light-brown macules with a velvety to finely verrucous surface. Although the initial size is usually <1 cm, mature SKs can measure several centi-meters. With time, the lesions become thicker and assume a polypoidal appearance with an uneven surface. A greasy scale and a warty topography seem “stuck” on the dull or lackluster surface. Follicular prominence causes either a pale follicular plug within a darker lesion or the reverse. 

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There are five clinical types of SKs. The classic lesion (as previously described) has a mushroomlike configuration and was the type our patient demonstrated. Small polypoidal lesions, commonly referred to as “skin tags,” are rough-surfaced polyps most commonly noted on the neck, under the breasts, or in the axillae. Stucco keratoses are numerous, small, superficial, grayish-white, flat, keratotic lesions that favor the dorsal feet, ankles, hands, and forearms of adults. These acanthotic growths range from 3 to 4 mm. Clinically, they resemble small flat warts. Irritated SKs exhibit eczematous changes with erythema and crusting of skin in and around the lesion. Although trauma is sometimes the cause of inflammation, in most cases, no antecedent event is reported. Dermatosis papulosa nigra affects the face, especially the upper cheeks and lateral orbital areas, of black patients. The lesions are small and heavily pigmented with a minimal keratotic element. Over time, many of these lesions also become pedunculated. 

Although SKs are benign, many patients associate them with aging and find them annoying because they can catch on clothing or cause itching. In addition, SKs can be confused with nevi and raise the specter in some patients’ minds of malignant melanoma. 

Reports in the literature note an association known as the sign of Leser-Trélat, linking SKs with adenocarcinomas of the stomach, colon, and breast; lymphomas; leukemias; and melanomas, but evidence to support such relationships is meager at best.  

Histologically, the basaloid cells in this entity fail to differentiate like normal epidermal basal cells, although they multiply, keratinize, and mature into squamous cells. By biologic assessments, SKs consist of accumulated senescent epidermal cells in G1 arrest of the cell cycle.  

SKs that bother patients either functionally or cosmetically can be treated. The most common mode of treatment is cryotherapy, although surgical excision, curettage, electrodesiccation, and lasers have been utilized. Topical agents routinely are not advocated; however, they can be helpful in thick, hyperkeratotic SKs. The use of keratolytics for SKs is not new, and various proteases and keratolytics have been used with some success, including tazarotene (Tazorac) and benzoyl peroxide in consort with a tertiary amine.1,2 We recently published our work on the use of urea as a keratolytic agent with occlusion in the topical treatment of hyperkeratotic SKs.3 Urea is a keratolytic agent that partially unfolds protein molecules by disrupting noncovalent interactions and hastens the natural sloughing of excess stratum corneum. Additionally, we are conducting further trials with various keratolytic agents using other delivery systems in the hopes of better meeting patient needs in the treatment of SKs. 

We instructed our patient to apply a 50% urea ointment (Keralac) to the lesion nightly and cover it with a Band-Aid. Once or twice a week, she scraped the lesion’s surface with a fingernail to see if she could flake some of it off. After she had removed the bulk of the lesion over a two-month period, we used liquid nitrogen on the flattened lesion, with results that proved satisfactory to the woman’s daughters.

Dr. Burkhart is clinical professor of dermatology at the University of Toledo College  of Medicine in Ohio and clinical assistant professor of dermatology at Ohio University College of Osteopathic Medicine, in Athens.


1. Herron MD, Bowen AR, Krueger GG. Seborrheic keratoses: a study comparing the standard cryosurgery with topical calcipotriene, topical tazarotene, and topical imiquimod. Int J Dermatol. 2004;43:300-302.
2. Burkhart CG. The search for topical treatments for seborrheic keratoses continues. Int J Dermatol. 2006;45:1110-1112.
3. Burkhart CG, Burkhart CN. Use of a keratolytic agent with occlusion for topical treatment of hyperkeratotic seborrheic keratoses. Skinmed. 2008;7:15-18.