What are
Actinic Keratoses?
Actinic keratoses (AKs) are known as the early beginnings of skin
cancer. This most common lesion of the outermost layer of the
skin (epidermis) is caused by long-term exposure to sunlight (specifically
to ultraviolet wavelengths). AKs are most likely to appear after
age 40-50, and years of chronic exposure to the sun. However,
in geographic areas with year-round high-intensity sunlight (e.g.,
Florida, southern California) AKs are now found in persons as
young as the teens and twenties. The incidence of AKs is over
50 percent in older, fair-skinned persons in hot, sunny geographic
areas.
AKs are defined
as a cutaneous dysplasia 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 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.
© American Academy of Dermatology, 2001. All
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