A seborrheic keratosis is a usually harmless skin growth, tumor or lesion on an area of the skin where hair grows, such as the head, neck or trunk. Seborrheic keratoses can vary in appearance; are usually tan to dark brown; and have a rough, wart-like surface that can make them appear "stuck" on the skin.
A doctor should examine the growths to rule out cancer. Many people have them removed for cosmetic reasons, but removing them may be medically necessary if they bleed, itch, cause pain or obstruct vision.
Source: Prepared by the Editors of The Johns Hopkins Medical Letter: Health After 50