What is actinic keratosis?

Updated: Jun 03, 2021
  • Author: James M Spencer, MD; Chief Editor: William D James, MD  more...
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Actinic keratosis (AK) is a UV light–induced lesion of the skin that may progress to invasive squamous cell carcinoma. [18, 19, 20] It is by far the most common lesion with malignant potential to arise on the skin. Actinic keratosis is seen in fair-skinned persons on skin areas that have had long-term sun exposure. [5] In Australia, the country with the highest skin cancer rate in the world, the prevalence of actinic keratosis among adults older than 40 years has been reported to range from 40-60%. [21]

The premalignant nature of actinic keratosis was recognized almost 100 years ago, and the name literally means thickened scaly growth (keratosis) caused by sunlight (actinic). In the United States, actinic keratosis represents the second most frequent reason for patients to visit a dermatologist. [22]

An actinic keratosis may follow 1 of 3 paths; it may regress, it may persist unchanged, or it may progress to invasive squamous cell carcinoma. The actual percentage that progress to invasive squamous cell carcinoma remains unknown, and estimates have varied from as low as 0.1% to as high as 10%. [18, 23]

In 2009, Criscione and colleagues conducted a study examining the progression of actinic keratoses to squamous cell carcinoma and basal cell carcinoma. [24] The study examined 7784 actinic keratoses in a high-risk population and found that nearly 65% of primary squamous cell carcinomas and 36% of primary basal cell carcinomas arise from clinically diagnosed actinic keratoses. Furthermore, risk of progression of actinic keratosis to squamous cell carcinoma was 0.60% at 1 year and 2.57% at 4 years, which is 6-8 times more frequent than has been reported in some prior studies.

Although it is impossible to predict which individual lesion will follow which course, as most patients have many lesions, accessing risk becomes more significant and aids in tailoring treatments. Overall, actinic keratoses can be safely and effectively eradicated, and, therefore, therapy is warranted.

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