Seborrheic keratoses (SKs) are extremely common benign neoplasms of the epidermis that typically appear on the chest and the back. There can be 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.  

A lichenoid keratosis is an inflamed seborrheic keratosis that presents as a pink shiny papule or plaque with an appearance that resembles that of a nodular or cystic basal cell cancer.

Dermatosis papulosa nigra is a term given to the papular seborrheic keratoses (most often seen as dark brown 1-3 mm papules) on the face of individuals with darker skin colors.

Relatively rapid onset of numerous SKs may be a cutaneous sign of internal malignancy. Multiple eruptive SKs in association with a visceral cancer is referred to as the sign of Leser-Trélat. The most common associated malignancy is adenocarcinoma of the gastrointestinal tract.