Actinic keratosis (AK) is a common skin condition resulting from prolonged ultraviolet (UV) radiation exposure. It appears as rough, scaly patches. While individual AK lesions do not spread like an infection, new ones can develop in other sun-exposed areas. AK is considered precancerous, meaning it has the potential to develop into skin cancer if left untreated.
What Actinic Keratosis Is
Actinic keratosis is characterized by rough, dry, or scaly patches on the skin. These lesions can vary in appearance, from flat or slightly raised bumps to wart-like surfaces, and often feel like sandpaper. They commonly develop on sun-exposed areas like the face, ears, lips, scalp, neck, hands, forearms, and shoulders. The primary cause of AKs is cumulative damage to skin cells’ DNA from long-term exposure to UV radiation. AK is classified as a precancerous lesion, representing an early stage of abnormal skin cell development.
Understanding How AK Appears
Actinic keratosis lesions do not “spread” across the skin surface like a rash or infection. Each lesion develops independently due to localized sun damage. However, new AKs commonly appear in other sun-exposed areas.
This phenomenon is known as “field cancerization,” where extensive UV exposure causes widespread genetic alterations in a region of skin. Importantly, AK itself does not metastasize, meaning it does not spread to distant organs. If an AK lesion progresses to an invasive skin cancer, then the potential for metastasis arises.
The Risk of Transformation to Cancer
While actinic keratosis does not metastasize on its own, it carries a risk of transforming into a type of skin cancer called squamous cell carcinoma (SCC). AKs are considered an early form of cutaneous SCC. The estimated rate of progression from an individual AK lesion to SCC can vary, with some studies suggesting a lifetime risk of less than 1% per year, while others report a 5% to 10% risk or up to 20% for untreated lesions. A large study found that after 10 years, the incidence of SCC in patients originally diagnosed with AK was 17.1%.
Several factors can increase the likelihood of an AK progressing to SCC. Continued exposure to UV radiation further damages skin cells, contributing to malignant transformation. A weakened immune system, whether due to illness, medications, or organ transplant, significantly increases this risk. Additionally, certain characteristics such as older age, fair skin type, and male sex are associated with a higher risk of developing AKs and their progression to SCC. Given this potential for progression, monitoring and appropriate treatment of AKs are important steps in preventing the development of invasive skin cancer.
Managing Actinic Keratosis
Diagnosis of actinic keratosis typically involves a visual examination by a healthcare provider. In cases where the diagnosis is uncertain or to rule out skin cancer, a skin biopsy may be performed. Treatment options for AK aim to remove or destroy the affected skin cells.
Common procedures include:
Cryotherapy, which involves freezing the lesions with liquid nitrogen.
Topical medications, such as fluorouracil cream, imiquimod cream, or diclofenac gel, which are applied to the skin over several weeks or months to eliminate abnormal cells.
Photodynamic therapy (PDT), where a light-sensitizing solution is applied to the skin, followed by exposure to a special light that destroys the AKs.
Surgical removal for individual lesions.
Preventing new actinic keratoses and reducing the risk of progression involves consistent sun protection. This includes daily application of broad-spectrum sunscreen with an SPF of 30 or higher, even on cloudy days, and reapplying it frequently, especially after swimming or sweating. Wearing protective clothing, such as wide-brimmed hats, long-sleeved shirts, and sunglasses, helps shield the skin from direct sunlight. Seeking shade, particularly during peak sun hours between 10 a.m. and 4 p.m., is also advised. Avoiding tanning beds, which emit harmful UV radiation, is another important preventive measure.