I. Definition:

A solar or actinic keratosis is a precancerous skin growth caused by sun damage. Solar keratoses are difficult to see, they feel rough and are sometimes scaly. Solar keratoses are not skin cancer, but if left untreated they can turn into skin cancer.

II. Causes: 

Repeated, prolonged sun exposure causes skin damage which may develop into a solar keratosis. The sun damage responsible for a solar keratosis usually occurred years before the lesion forms.

III. Treatment:

Solar keratoses can be removed by surgery or by freezing with liquid nitrogen. Sometimes we are not sure whether the growth is a solar keratosis or an early cancer. When there is doubt, we like to cut the growth off and send it for microscopic analysis (biopsy). Healing after removal usually takes one to two weeks and leaves a flat white scar.

When there are many keratoses, a useful treatment is 5-FU (5-fluorouracil) cream. The medication is applied to the involved area twice a day for 4 weeks. The treated area becomes red, raw, and irritated. Healing starts when the 5-FU cream is stopped. A complete course of 5-FU, including healing time, can take up to two months.

New solar keratoses and skin cancers often arise near or at the location where old ones have been treated. This is because the skin cells nearby have just as much damage as the ones already treated. Once a person develops solar keratoses they need to be checked every six to twelve months for new ones.     

 IV. Prevention:

The above treatments do not prevent new solar keratoses from forming. Daily sunscreen use (SPF 15 or higher) will help some, but most of the damage causing these growths occurred many years ago.

Retin-A (Renova), alpha hydroxyacid lotion and beta hydroxyacid applied daily to areas of sun damaged skin will reverse some microscopic keratoses and help prevent new ones.

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