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Actinic Keratosis

Actinic keratosis (senile or solar keratosis) is the most common precancerous dermatosis.
Single or multiple lesions develop on areas exposed to the sun, such as the face, the backs of
the hands, the forearms, the neck, and balding scalp. Actinic cheilitis denotes scaly or
crusted patches of precancer on the vermilion of the lips. 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. These lesions
result in squamous cell carcinomas that occasionally metastasize [see Malignant Epithelial
Tumors, Squamous Cell Carcinoma, below].1,14 Signs that an actinic keratosis has become
malignant are elevation, ulceration or inflammation, and recent enlargement, usually to a
diameter greater than actinic keratosis.

On histologic examination, the epidermis may be thickened or atrophic. Atypical cells tend
to invade the most superficial portion.

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.17 For patients who have numerous actinic keratoses, topical
chemotherapy with one to five percent fluorouracil is practical and effective. The solution,
cream, or gel is applied once or twice a day for at least 10 to 14 days, until a pronounced
erythematous reaction ensues in the affected skin areas . Crusting and
desquamation of the keratoses occur.

Masoprocol cream is a newer topical chemotherapy for actinic keratoses that is applied
twice daily for four weeks to eradicate the lesions. This agent has the advantage of causing
significantly less local irritation than fluorouracil. However, it can cause an allergic contact
dermatitis in about 10 percent of persons treated. Other methods, such as chemical peels and
sun spot.