Actinic keratoses (AKs) are common pre-cancerous skin lesions that occur on sun-exposed areas, particularly in blond or red-haired, fair-skinned individuals with green or blue eyes. These lesions relate most directly to cumulative sun exposure. AKs represent the initial manifestation of abnormal proliferation of skin cells (keratinocytes) with the possibility of progression to squamous cell carcinoma in situ (SCC in situ), superficial basal cell carcinoma (sBCC), and invasive squamous cell carcinoma (SCC) and basal cell carcinoma (BCC).

Actinic Keratosis (Photos: Anetta Reszko)

AKs are red, pink, or light lesions with a scaly, rough surface. They frequently occur on sun-exposed areas and are especially common on the balding scalp, forehead, face, dorsal forearms, and hands.   Early subclinical (non-visible) AKs are estimated to occur up to 10 times more often than clinically visible AKs, particularly on sun-exposed skin.

Clinically, AKs have three possible behavioral patterns:

• spontaneous regression
• persistence
• progression into invasive SCC or BCC

The risk of progression of an AK to invasive SCC is between 0.025 and 16 percent per year. The long-term risk of development of invasive SCC in patients with multiple AKs has been estimated to be as high as 10 percent. The majority of SCCs, approximately 60 to 65 percent, arise within prior AKs. Spontaneous temporary regression of AKs has been reported in as high as 25.9 percent of patients over a 12-month period, although a 15 percent recurrence rate was noted at subsequent follow-up.

Factors linked to the development and progression of AKs include:

• exposure to ultraviolet B (UVB) light; UVB causes mutations of the main tumor suppressor genes
• genetic disorders (i.e., xeroderma pigmentosum) or melanin deficiency (albinism)
• older age
• male gender
• anatomical location; over 80 percent of AKs are located on the head and neck, dorsal forearms, and hands
• history of immunosuppression; solid organ transplant patients are at significantly increased risk

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