Premalignant skin lesions.

The most common precancerous skin lesions are actinic keratoses, Bowen's disease, and keratoacanthoma. Actinic keratoses appear over the exposed areas of the body as the result of actinic radiation. Bowen's disease is most probably secondary to the effects of internal carcinogens. Keratoacanthomas are self-limited lesions that occasionally may transform into invasive squamous cell carcinoma.