Seborrheic keratoses are raised growths on the skin. Seborrheic means greasy and keratosis means thickening of the skin. There may be just one or clusters of dozens. They are usually start off light tan, and then may darken to dark brown or nearly black. They may be oval spots a fraction of an inch across, or form long Christmas tree like patterns on the torso inches long. The consistent feature of seborrheic keratoses is their waxy, pasted-on or stuck-on look. The look is often compared to brown candle wax that was dropped onto the skin.

Seborrheic keratosis consists of benign, verrucous (wart-like), often pigmented, greasy lesions consisting of proliferating epidermal cells which usually occur after the third decade.