Actinic keratoses (AKs) are rough scaly spots on sun-damaged skin (Fig. 1). Other synonymous terms used include 'solar keratosis' and 'keratosis senilis'. in the UK, the incidence of new AKs is estimated as 149 per 1000 patient-years (Harvey, Frankel, Marks, Shalom, Nolan-Farrell, 1996) and 19-23 of people over the age of 60 have at least one AK (Harvey et al., 1996; Memon, Tomenson, Bothwell, Friedmann, 2000). AKs represent focal areas of abnormal keratinocyte proliferation and differentiation. In all cases there is epithelial dysplasia; this may be restricted to the basal layer or extend through the full thickness of the lesion. There is never any invasion through the basement membrane zone into the dermis.
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