In actinic keratosis, lesions are round or irregularly shaped, erythematous or tan plaques with an adherent scaly or rough surface. They range in size from several millimeters to 1 cm or more. Locally invasive lesions have been reported to develop in 12 percent of patients with actinic keratoses. Signs that an actinic keratosis has become malignant are elevation, ulceration or inflammation, and recent enlargement, usually to a diameter greater than 1 cm. On histologic examination, the epidermis may be thickened or atrophic.
Atypical cells tend to invade the most superficial portion of the dermis.
An actinic keratosis is usually treated by liquid-nitrogen cryotherapy. Persistent, recurrent, or hypertrophic actinic keratoses may be removed by surgical excision or removed by scalpel with biopsy and curettage. For patients who have numerous actinic keratoses, topical chemotherapy with one to five percent fluorouracil is practical and effective. Crusting and desquamation of the keratoses occur, followed by reepithelialization. Masoprocol cream is a newer topical chemotherapy for actinic keratoses that is applied twice daily for four weeks to eradicate the lesions.