Also known as solar keratosis, actinic keratosis affects more than 10 million Americans. These precancerous growths on the skin are caused by overexposure to the sun over a long period of time. They are characterized by rough dry lesions or patches that appear on sun-exposed areas of the skin, such as the face, back of hands, arms, scalp or shoulders. The lesions may be red, pink, gray or skin colored. Lesions often begin as flat, scaly areas and develop into a rough-textured surface. Sometimes it is easier to feel a growth than it is to see it.