An actinic keratosis is a rough, scaly patch on your skin that develops from years of exposure to the sun. It's most commonly found on your face, lips, ears, back of your hands, forearms, scalp or neck. Also known as solar keratosis, an actinic keratosis enlarges slowly and usually causes no signs or symptoms other than a patch or small spot on your skin.
Over time, actinic keratoses may develop into invasive squamous cell carcinoma; according to one study of almost 7000 patients, among the small percentage of actinic keratoses that progress into squamous cell carcinoma, the length of time for this transformation to occur was approximately 2 years.Cells within actinic keratoses (AKs) show characteristic UV-induced gene mutations.
The morphology of atypical cells in both actinic keratosis and squamous cell carcinoma is identical. The risk of progression to squamous cell carcinoma is minimal, but up to 60% of squamous cell carcinoma cases begin as actinic keratosis. Regression of actinic keratosis occurs when sun exposure is decreased.
ALA–PDT and MAL–PDT are both useful therapies for the treatment of AKs and photorejuvenation. Clinical trials have shown efficacy with both modalities in treating AKs and more work has been performed with ALA in the treatment of photorejuvenation, although MAL will work here too. Consensus papers for both therapies, which are useful guides for clinicians, have been published and may be helpful to those looking to enter the PDT field or those looking to expand their knowledge base.