Seborrheic keratoses (SKs) are extremely common benign neoplasms of the epidermis that typically appear on the chest and the back. There can be a few or hundreds of these raised, "stuck-on"-appearing papules and plaques with well-defined borders. The etiology is unknown, although there is a familial trait for the development of multiple SKs with an autosomal dominant mode of inheritance. SKs tend to increase in incidence and number with increasing age. They may start out as a flat, wrinkled plaque with a "postage stamp" appearance (flat seborrheic keratosis). SKs are asymptomatic, but when irritated or traumatized, they may become pruritic or painful with associated redness or bleeding.

SKs are rarely seen on the penile skin. SKs in the genital area have been associated with the presence of human papillomavirus (HPV) infection as identified by polymerase chain reaction.