Seborrheic keratoses are one of the most common skin tumors.[1]Pierson D, Bandel C, Ehrig T, et al. Benign epidermal tumors and proliferations. In: Bolognia JL, Jorizzo JL, Rapini RP, eds. Dermatology. London: Mosby; 2003:597-602.[2]MacKie RM, Quinn AG. Non-melanoma skin cancer and other epidermal skin tumors. In: Burns T, Breathnach SM, Cox N, et al, eds. Rook's textbook of dermatology. 7th ed. Oxford, UK: Blackwell; 2004:36-45.[3]Weedon D. Chapter 31: Tumors of the epidermis. In: Weedon D. Skin pathology. 2nd ed. London: Churchill Livingstone; 2002:765-771.[4]Altmeyer P, Bacharach-Buhles M, eds. Enzyklopadie dermatologie, allergologie, umweltmedizin. Berlin: Springer; 2002. They are uncommon in people under 30 years of age. Men and women are affected equally. The prevalence of seborrheic keratosis increases with age and sun exposure. In people with white skin, they are common over the age of 60 years. The trunk and forehead are most commonly affected.[9]Jackson JM, Alexis A, Berman B, et al. Current understanding of seborrheic keratosis: prevalence, etiology, clinical presentation, diagnosis, and management. J Drugs Dermatol. 2015 Oct;14(10):1119-25.
http://www.ncbi.nlm.nih.gov/pubmed/26461823?tool=bestpractice.com
There are many different subtypes of seborrheic keratosis. Dermatosis papulosa nigra is a common subtype of seborrheic keratosis which is more prevalent in people with brown and black skin (Fitzpatrick skin type IV, V, or VI). Lesions usually start to appear in adolescence and are usually found on the face, neck, and chest; incidence increases with age.[10]Garcia MS, Azari R, Eisen DB. Treatment of dermatosis papulosa nigra in 10 patients: a comparison trial of electrodesiccation, pulsed dye laser, and curettage. Dermatol Surg. 2010 Dec;36(12):1968-72.
http://www.ncbi.nlm.nih.gov/pubmed/21040130?tool=bestpractice.com