Actinic Keratosis

Abstract

Actinic keratosis is the topic of this book organized in 21 chapters. Actinic keratosis (AKs), also known as solar keratosis, are common pre-cancerous skin lesions that, occurring predominantly in the middle-aged and elderly, affect sun-exposed areas, such as face, V of chest, and backs of the arms and hands. They are of public health importance because their presence significantly raise risks of skin cancers, such as basal cell carcinoma, squamous cell carcinoma (SCC) and melanoma. AKs are usually less than one centimetre in size and appear as slightly elevated, rough surfaced lesions. The presence of hyperkeratosis may make it difficult to distinguish between an actinic keratosis and a squamous cell carcinoma or an irritated seborrheic dermatitis. Although the natural history of AK is poorly understood, it is associated with immunosuppression so that the immune surveillance and the sun protection play a key role to prevent the skin tumour genesis. However, it is clear from studies conducted in many different populations that AKs are a public health burden in sun-sensitive people living without adequate sun protection at low latitudes. Moreover, the major risk factors are male sex, advanced age, sensitive complexion, high lifetime sun exposure, and prolonged immunosuppression. In any way, a very small proportion of AKs undergo malignant transformation, also if the precise rate of transformation is unknown due to the inaccuracies in monitoring these skin lesions over time.