Actinic keratosis (Q43975)

Actinic keratoses (AKs) are focal areas of abnormal keratinocyte proliferation and differentiation induced by chronic exposure to ultraviolet radiation. They are very common on sun-exposed skin of fair-skinned individuals who have had excessive exposure to sunlight. Initially flat scaly papules, they may become significantly elevated from the skin surface by producing dense adherent keratin or as a result of unregulated cellular proliferation which may progress to frank carcinoma in situ or invasive squamous cell carcinoma.