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II. Causes:
AKs are defined as a cutaneous dysplasia
skin growth of the
epidermis (the outermost layer of skin). In everyday terms, AKs are an
alteration in size, shape and organization of skin cells. The cells most
affected in AKs are the keratinocytes, the tough-walled cells that make up more
than 90 percent of the epidermis and give the skin its texture. Cellular
alterations in AKs may extend into the dermis, the layer of skin under
the epidermis. The most significant cause of actinic keratoses is long-term
exposure to sunlight, and specifically to the ultraviolet wavelengths of solar
radiation. The most significant predisposing factor to AKs is fair
skin.
The alteration in skin growth and differentiation of keratinocytes is manifested in the clinical features of AKs - rough, scaly skin,
"bumps" on the skin, mottled skin, and cutaneous horn. Alterations in cell
growth and differentiation also set the stage for transformation of AKs into
invasive squamous cell carcinoma.
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