About actinic keratosis (keratoses)
An actinic keratosis is often better felt than seen, appearing as a poorly defined red-yellow rough patch or papule with adherent scale. Actinic keratoses are found in sun-exposed areas such as the head, neck, forearms and back of the hands. Other signs of photoaging, such as solar elastosis and lentigines, are usually present as well. Actinic keratosis is considered a pre-malignant lesion in which the precancerous cells are located only in the superficial epidermal layer. Actinic keratoses are the result of sun damage, specifically exposure to ultraviolet light. It is more common in light skinned persons, and the incidence increases with nearness to the equator.
What else looks like actinic keratosis?
Actinic keratosis must be distinguished from other growths, including: seborrheic keratosis, squamous cell carcinoma, superficial basal cell carcinoma, and Bowen’s disease (in situ squamous cell carcinoma)
How is actinic keratosis diagnosed?
A history of sun exposure is usually present. Patients are often fair-skinned and may report a history of skin cancer. The lesions of actinic keratoses may be difficult to detect and can often be more easily detected by feeling carefully for a rough scaling patch. Biopsy is usually not necessary but may sometimes be required to rule out malignancy.
How is actinic keratosis treated?
Actinic keratosis can be destroyed with liquid nitrogen cryotherapy. For widespread lesions, 5-fluorouacil (5-FU) cream (e.g. Efudex) applied for several weeks will result in an inflammatory reaction and subsequent crusting and destruction of the lesions. Imiquimod (e.g. Aldara) is another option. Normal skin has only a minor reaction to 5-fluorouracil or imiquimod. The use of either agent results in an unsightly appearance for several days to weeks but is usually very effective. Multiple treatment courses may be required for clearance. Chemical peels with trichloroacetic acid (TCA) can also be used to treat large areas. Photodynamic therapy is also effective for large areas.
Sun protection and sun avoidance is mandatory. It prevents new lesions from forming and may speed the resolution of existing ones. Sunscreen with an SPF of at least 15 to 30, avoidance of midday sun, and protective clothing are all necessary.
What is the prognosis for actinic keratosis?
Some lesions spontaneously resolve. This is more likely to occur with the consistent adoption of sun-protective measures. As a pre-malignant lesion, some (estimated to be less that 0.1% per year) develop into squamous cell carcinoma. Actinic keratoses continue to develop over time in previously sun damaged skin. Repeat treatments with 5-FU, imiquimod or photodynamic therapy, or removal of isolated lesions with cryotherapy, may be required. Surveillance is necessary for new actinic keratoses or evolution into, or simultaneous development of, skin cancer. Cryotherapy can result in scarring.
