Hi everyone. Today I want to talk about some new information coming out about actinic keratoses, which are thought to be precancerous lesions commonly found on sun exposed areas of skin. These scaly, usually somewhat reddish skin lesions are commonly treated with liquid nitrogen in order to prevent them from possibly evolving into squamous cell carcinoma. Other common treatments include topical creams such as imiquimod, diclofenac, and fluorouracil. People tend to have multiple actinic keratoses, with more occurring in people with more cumulative sun exposure over the course of many years. These lesions are one of the common reasons for office visits to the dermatologist.
The traditional thought on these lesions is that they can evolve into squamous cell carcinoma over time so we treat all these lesions as it is difficult to predict which would turn into cancer. But we never have had good studies that would allow to know which of these lesions and how many of them would become cancerous. More recent information shows that these common lesions are more complicated than simply being pre-squamous cell carcinomas. New research now suggests that after diagnosis, the rate at which these lesions evolve into squamous cell carcinoma is 0.6% at one year and 2.6% after four years. Also, during this study, they found that some lesions would “come and go” over the course of time. This is not expected for lesions that would progress from normal to skin cancer. Many individuals come in for skin exams with greater than 15 or 20 of these lesions at any given time. This new information suggests that about 1 out of every 40 lesions will turn into squamous cell carcinoma. This is important as it shows that people with many lesions will likely get skin cancer rather than just maintaining a precancerous stage for many years.
Another interesting finding is that after four years, over 1% of the diagnosed actinic keratoses evolved into basal cell carcinoma. This skin cancer is the most common and usually most easily treated skin cancer but was always thought to be separate from the actinic keratosis. This is unexpected as the dogma for many years was that the actinic keratoses are precursors of squamous cell carcinoma only. So this new information now makes us realize we do not know as much about these common lesions as previously thought. Although this new information will not necessarily change our approach to treating these lesions, we now know that our knowledge of actinic keratoses is limited and more research is needed.
While this information is important, it is new and the studies on which this information is based may have several flaws. However, it is clear that more studies will help us clarify how actinic keratoses become cancerous and hopefully allow us to identify the ones that are at higher risk of becoming cancerous. Thicker and bigger lesions are more likely to become cancerous but it would be helpful to have other guidelines to know which lesions may be most likely to evolve into cancer. Although liquid nitrogen is the most common treatment, remember to alert your dermatologist to any lesions that were treated in the past without resolution. Lesions that persist through multiple treatments are more likely to be cancerous. And of course, prevention is the best treatment so remember to wear sunscreen, protective clothing, and avoid prolonged sun exposure in the afternoon hours.