More than ten million Americans have pre-cancerous growths, known as actinic keratoses, on their skin. What exactly are actinic keratoses? Actinic keratoses, or AKs, are a common skin condition characterized by rough, scaly patches, on the top layer of skin. AKs occur due to sun exposure over long periods of time. Although AKs are not actually cancer they are classified as the earliest stage in its development. AKs are not always dangerous, but 16% of untreated cases will grow into squamous cell carcinoma, a type of skin cancer. All AKs develop from keratinocytes, which are the tough-walled cells that make up 90% of the skin's outer layer. Years of sun damage can cause these cells to change in size and shape, resulting in the skin lesions that are characteristic of AKs. AKs usually develop on areas of the skin that receive the most exposure to sunlight. These include the face, ears, scalp, neck, forearms, and the backs of hands. Sometimes, lesions appear on the lips, a condition that is called actinic cheilitis. AKs vary in appearance. They can range in size from that of a pinhead to a quarter, and in color from light tan to red. On occasion, a lesion will grow into a small horn, called a cutaneous horn. Almost anyone can get AKs, however some people are more prone to them than others. It is certainly true that those who have spent a great amount of time in the sun are more likely to develop the growths. Because AKs develop with cumulative exposure to the sun's ultraviolet rays, the skin lesions are most often found in people 50 years of age or older. Earlier occurrence is rare and can usually be linked to tanning beds and sunny locations. People with fair skin, light hair, and light eyes are usually more sensitive to the sun's rays, and therefore more likely to develop AKs on their skin. For this reason, individuals with darker skin types rarely develop these lesions. The prevalence of AKs is higher in men than in women. Although no one knows why, it has been theorized that this is due to greater likelihood that men will have outdoor occupations, and thus receive greater sun exposure. A weakened immune system, or immunosuppression, can also increase the odds of developing AKs. Many factors can stifle the immune system, among them: taking medication to prevent organ rejection, chemotherapy, and HIV. Because AKs can progress to become squamous cell carcinoma, it's important for people with AKs to be under a dermatologist's care. A dermatologist will usually be able to treat actinic keratoses safely and effectively, ensuring that you stay healthy. Remember, see your doctor immediately if you have any concerns about your skin. Want to learn more? Check out other videos and sources on this site for more information.