A person who has been treated for actinic keratoses (AKs) is always considered at risk for new lesions, especially if the person has AK risk factors of white skin, red or blond hair, light-colored eyes and chronic sun exposure. While treatment of AKs is usually successful, repeated formation of new lesions increases risk for malignant transformation of the AK lesions. Many people at high risk have new AK lesions every year. A person who has recurrent AKs should be examined regularly by a dermatologist, and should also self-examine to detect new lesions at early stages of development.

Actinic keratoses (AKs) are lesions that can be the early beginnings of skin cancer. If they undergo malignant transformation, AKs evolve into squamous-cell carcinoma, a common form of skin cancer.

Left untreated, AKs can transform into squamous-cell carcinoma in some patients—in less than 1 percent to as many as 16 percent in various studies (Glogau RG. The risk of progression to invasive disease. J Am Acad Dermatol 2000; 42:S23-24). Most squamous-cell carcinomas that develop from AKs are low-grade malignancies that can metastasize (spread) if they are ignored and allowed to invade deeper tissues. However, even if it does not metastasize, a squamous-cell carcinoma may spread locally and cause substantial local tissue damage if not treated early.

Squamous-cell carcinoma may be more invasive and likely to metastasize;

1. When it arises in the lip or scalp
2. When it is the type called adenoid squamous cell carcinoma and is larger than 2.5 centimeters in diameter.

In the great majority of cases, AK lesions and squamous-cell carcinomas that arise from AK lesions are successfully treated with complete removal of all keratotic and/or malignant tissue (Click on Treatment of Actinic Keratoses for information about types of treatment for AKs).Treatment of AKs before malignant transformation occurs is always preferable to finding that the AK lesion has evolved into squamous-cell carcinoma.

Prevention of AK Lesions After Treatment
If you have been treated for AKs and/or squamous-cell carcinoma you should understand that you are at moderate to high risk for new lesions. You should take all the necessary protective measures to prevent new lesions:

• Consistent use of sunscreen and protective clothing when you are outdoors.
• Avoid sun exposure at peak hours of sunlight, between 10 a.m. and 4 p.m.

In addition, if you have been treated for AKs you should:

• Learn how to recognize AKs and self-examine your skin regularly to identify any new lesions at the earliest stage of development.
• Schedule regular follow-up examinations by a dermatologist.

Some medications may be helpful in preventing new AKs. Topical tretinoin (a vitamin A derivative used as a treatment for aging skin) has been shown to reduce onset of new AK lesions. A dermatologist should be consulted regarding the use of tretinoin, a prescribed topical medication.

References
AAD Guidelines of Care for Actinic Keratoses