The hidden danger of sun exposure: actinic keratoses--small scaly lesions that feel like sandpaper to the touch--can progress to an invasive form of skin cancer if left untreated.

• Author: Jorizzo, Joseph
• Position: Medicine & Health

EVERYONE looks forward to weather forecasts with bright, sunny days. However, one must be aware of the anger to the skin that is posed by spending time outdoors--sometimes with deadly consequences. Most people know that the sun can accelerate the signs of aging, such as wrinkles, fine lines, and age spots, but many are unaware of some of the hidden perils of cumulative exposure.

Excessive unprotected sun exposure can lead to skin cancer, including melanoma, which affects an estimated 44,000 Americans annually. While melanoma, the deadliest of all skin cancers, can be cured if caught early enough, there is another type that is much more common, though many individuals may not even know that they have it.

Actinic keratoses (AKs) are often invisible to the naked eye. Forty-six million Americans--one-sixth of the population--will develop an actinic keratosis during their lifetime, according to the Skin Cancer Foundation. The appearance of an actinic keratosis can be the first step in the development of skin cancer.

Although it often is referred to as a "pre-cancer," dermatologists now consider AK to be an "evolving cancer" because once skin cells become abnormal, that means cancer. This is somewhat analogous to an abnormal PAP smear in women. AKs themselves are not life-threatening, but, if let untreated, they can progress to an invasive form of skin cancer called squamous cell carcinoma.

AKs are small scaly lesions that begin under the skin's surface and then emerge as rough areas that feel like sandpaper to the touch. They can be pink, tan, red, or the same color as the skin, so they are more easily recognized by touch rather than sight. Generally, AKs range from an eighth to a quarter of an inch in size. Actinic keratoses are typically found on those parts of the body that receive the most sun exposure, such as the face, ears, lips, neck, back of hands, and forearms.

AKs usually occur in clusters, so where you notice one, it is a safe bet that there are more lurking under the surface in that same general area. This occurs because the ultraviolet damage from the sun produces a field of altered cells that become actinic keratoses.

People most at risk for this disease are those over the age of 50 who have had a significant amount of sun exposure or a history of repeated sunburns. Also vulnerable are those with fair skin, blond or red hair, and blue, green, or gray eyes. Individuals who are darker-skinned can develop actinic keratoses if they...