Actinic keratosis is a skin condition characterized by rough, scaly patches that develop after years of exposure to ultraviolet (UV) light. Also known as solar keratosis, this condition is very common. The term “actinic” originates from Greek, meaning “caused by sunlight,” while “keratosis” refers to thickened skin. These growths are a direct result of cumulative sun damage over a person’s lifetime.
The Link to Squamous Cell Carcinoma
Actinic keratosis (AK) is classified as a precancerous condition, which means the skin cells in the affected area are abnormal and have the potential to develop into a form of skin cancer. Specifically, AK is a precursor to cutaneous squamous cell carcinoma (cSCC), the second most common type of skin cancer. Studies show that a significant percentage of SCCs arise from pre-existing AK lesions. This transition is a gradual process involving genetic alterations in skin cells called keratinocytes, triggered by long-term UV radiation exposure.
While not every actinic keratosis will become cancerous, their presence signals a heightened risk. The estimated rate of an individual AK lesion progressing to SCC is low, but for individuals with multiple lesions, the long-term risk is significantly higher, estimated to be between 6% and 10% over 10 years. Because it is impossible to predict which specific lesion will progress, dermatologists recommend treating all diagnosed AKs as a preventative measure.
The connection is so established that some dermatologists consider actinic keratosis to be the earliest form of SCC, sometimes referred to as SCC in situ. An individual with multiple actinic keratoses is also at a higher risk for developing other types of skin cancer. The presence of these lesions serves as a clear indicator of significant sun damage, a primary risk factor for all forms of skin cancer. Therefore, addressing AKs is a proactive step in skin cancer prevention.
Identifying Actinic Keratosis on the Skin
Actinic keratoses are often more easily felt than seen, with a texture compared to sandpaper. The lesions begin as small, rough spots and evolve into scaly, crusty patches that are flat or slightly raised. They may also develop a harder, wart-like surface or form a raised, horn-shaped bump, ranging from a tiny spot to over an inch in diameter.
The color of an actinic keratosis is variable, appearing pink, red, tan, brown, silvery, or the same color as the surrounding skin. Symptoms can include itching, a burning sensation, or tenderness. While some are asymptomatic, lesions may become inflamed, bleed, or develop a persistent sore.
These growths appear on parts of the body with high cumulative sun exposure. Common locations include the face, lips, ears, neck, shoulders, and the scalp of individuals with thinning hair. They are also found on the back of the hands and forearms. A specific variant known as actinic cheilitis occurs on the lower lip.
Treatment Pathways for Actinic Keratosis
Medical treatment for existing actinic keratosis lesions is focused on removing the damaged cells. The choice of therapy depends on the number, location, and size of the lesions, as well as the patient’s overall health. Treatments are categorized as either spot treatments, which target individual lesions, or field treatments, which address a larger area of sun-damaged skin.
For isolated or a small number of lesions, cryotherapy is the most common approach. This procedure involves applying liquid nitrogen to freeze the targeted cells, causing them to blister or peel off. Another spot treatment is curettage and desiccation, where a doctor scrapes off the lesion and then uses an electric current to destroy any remaining abnormal cells.
When multiple lesions are present, field treatments are preferred. Topical creams and gels, such as 5-fluorouracil (5-FU) and imiquimod, are prescribed for at-home application to destroy the precancerous cells. Photodynamic therapy (PDT) is another field treatment where a light-sensitizing solution is applied to the skin and activated by a special light source. Chemical peels and laser therapy can also be used to remove the top layers of damaged skin.
Prevention and Key Risk Factors
The primary cause of actinic keratosis is cumulative exposure to ultraviolet (UV) radiation from the sun or artificial sources like tanning beds. Several factors heighten this risk, including having fair skin, blond or red hair, blue or green eyes, and skin that burns or freckles easily.
Other risk factors include being over the age of 40, having a weakened immune system, and being male. Living closer to the equator and a history of sunburns, especially in childhood, also increase the risk.
Preventing actinic keratosis involves diligent sun protection and regular skin monitoring. Effective strategies include:
- Using a broad-spectrum sunscreen with an SPF of 30 or higher.
- Wearing protective clothing, including long-sleeved shirts, pants, and a wide-brimmed hat.
- Seeking shade and avoiding sun exposure during peak hours, between 10 a.m. and 4 p.m.
- Performing regular skin self-exams to identify any new or changing spots.
- Getting annual professional skin examinations by a dermatologist.