Skin Cancer Pictures, Part IV: Non-Cancerous and Pre-Cancerous Skin Lesions

Actinic keratosis (also called solar keratosis) is a precancerous skin lesion usually caused by too much sun exposure. (It may also be caused by many other factors, such as radiation or arsenic exposure.) If left untreated, actinic keratoses can develop into a more invasive and potentially disfiguring skin cancer called squamous cell carcinoma. They appear predominantly on sun-exposed skin, such as the face, neck, back of the hands and forearms, upper chest, and upper back. Men may develop keratoses along the rim of the ear.