Actinic keratosis develops as a dry, flat, scaly spot and is caused by cumulative sun damage. The rough-textured lesion feels hard and calloused and can range from the size of a pinhead to larger than a quarter. Color may be skin tone to reddish brown.
Actinic keratoses take years to develop and appear on sun-exposed areas, such as the face, scalp, neck and hands. People who develop numerous actinic keratoses tend to have repeated occurrences throughout life.
Actinic keratoses or any skin lesions should never be dismissed as "just age spots." They have the potential to become squamous cell carcinoma, a serious form of skin cancer.
Source: Prepared by the Editors of The Johns Hopkins Medical Letter: Health After 50