Also known as solar keratosis, actinic keratosis (AK) is a rough, scaly patch on your skin due to years of sun exposure. Typically appearing in older adults, actinic keratosis usually takes years to develop and is considered to be precancerous because untreated it can advance to squamous cell carcinoma. It’s most commonly found on areas of skin typically exposed to the sun – face, lips, ears, back of your hands, forearms, scalp or neck.