Actinic Keratosis

Figure A


Figure B


Figure C

Actinic (solar) keratoses are found on sun-exposed skin of elderly white persons—in particular redheaded or blond patients, who tend to burn frequently and tan poorly.¹ Actinic keratoses are the most common sun-related growths in white persons. More than 60% of predisposed white persons older than 40 years have at least one actinic keratosis. About 2% to 5% of these lesions evolve into squamous cell carcinoma.

Most actinic keratoses consist of irregular white scaly papules with an erythematous base (A). Lesions with thickly keratotic surfaces are referred to as hypertrophic actinic keratoses (B), and they may be pigmented (C). They are usually 3 to 10 mm in diameter and enlarge gradually. Histologically, actinic keratoses demonstrate acanthosis, parakeratosis, and dyskeratoses with cellular atypia and keratinocytes with miotic figures that vary in size and shape.

Often, the upper back of a severely sun-damaged patient demonstrates patches of solar lentigines with distinct areas of scale. On palpation, the scaly areas demonstrate the slightly rough texture that characterizes actinic keratoses.

Actinic keratosis can flare and become more noticeable with immunosuppression, such as from acute sun exposure or chemotherapy (especially with systemic 5-fluorouracil).

The most common mimics of actinic keratosis are seborrheic keratosis, xerosis, seborrheic dermatitis, Bowen disease, superficial basal cell carcinoma, warts, porokeratosis, and squamous cell carcinoma. Less common varieties of actinic keratosis include hypertrophic actinic keratosis, pigmented actinic keratosis, and actinic keratosis related to cutaneous horn. Actinic keratosis on the lips is termed actinic cheilitis.

Treatment options include topical 5-fluorouracil, topical imiquimod, cryotherapy, curettage, photodynamic therapy, dermabrasion, chemical peels, carbon dioxide laser treatment, and (rarely) surgery.^2,3 I prefer cryotherapy for discrete lesions and topical 5-fluorouracil cream for large areas where I suspect there are clinically unapparent lesions.

Actinic keratosis has a good prognosis. Treatment is determined by the extent of the patient's lesions and his or her tolerance to pain and temporary inflammation. Such inflammation may be associated with cryotherapy, laser surgery, and topical 5-fluorouracil and imiquimod.