Statement on actinic keratosis: Actinic keratoses are cutaneous neoplasms displaying chromosomal abnormalities that occur primarily on sun-exposed skin surfaces. These premalignant lesions are usually a consequence of long-term solar radiation, but may also be caused by UV light exposure from artificial sources, x-irradiation, or exposure to polycylic aromatic hydocarbons.

Actinic keratoses range in size from 1 to 2 mm papules to large plaques. They may be flesh-colored, erythematous, or more deeply pigmented, and they usually have a hyperkeratotic surface. Horn formation can occur in any location. Although it is usually possible to diagnose actinic keratosis on the basis of the clinical appearance of a lesion, it may on occasion be difficult (or impossible) to distinguish one from a squamous cell carcinoma of the skin and other pathologic lesions without doing a skin biopsy (or other procedure) to obtain tissue for histologic examination.

It has been demonstrated that the p53 chromosomal mutation, found in more than 90% of human cutaneous squamous cell carcinomas, is also present in actinic keratoses. Estimates of the percentage of these chromosomally abnormal skin lesions that convert to squamous cell carcinoma vary from 0.25% to 20% per year for an individual lesion. Because patients often have multiple actinic keratoses (because of the field effect of solar radiation), the risks of conversion to a malignancy increase significantly. It is impossible to predict accurately in which patient a squamous cell carcinoma will develop. Most actinic keratoses and squamous cell carcinomas are asymptomatic. Once an actinic keratosis converts to a squamous cell carcinoma, it may bleed, ulcerate, become infected, destroy anatomic structures, or even spread to internal organs.

Actinic keratoses must be treated to prevent their conversion to squamous cell carcinoma. Treatment of these premalignant lesions avoids the potentially more invasive and extensive treatment of subsequent malignancy.

American Academy of Dermatology