DR P. MARAZZI / SCIENCE PHOTO LIBRARY DR P. MARAZZI / SCIENCE PHOTO LIBRARY
Solar keratosis on a 94-year-old man's scalp. Also known as actinic keratosis or solar warts, these dry and scaly, raised areas of skin may develop into a squamous cell carcinoma, a type of cancer. Treatment is by surgical removal or cryotherapy (a technique that uses freezing to remove unwanted tissue). Solar keratoses are caused by the ultraviolet radiation in sunlight, and so develop on exposed areas of skin such as the face or arms.
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