Madani S, Marwaha S, Dusendang JR, et al. - In this investigation involving 220,236 patients with actinic keratosis (AK) and 220,236 matched control patients (mean [SD] age, 64.1 [12.2] years; 231 248 [52.5%] female), researchers estimated the risk and identified risk factors for cutaneous squamous cell carcinoma (cSCC) development up to 10 years after diagnosis of AK. For this longitudinal cohort study, patients with AK and control participants were followed up for up to 10 years for incidence of cSCC. Data reported that the risk of cSCC was 1.92% per year after diagnosis of 1 or more AKs and 0.83% per year in matched controls without an AK diagnosis. Older patients were much more likely to develop cSCC than younger patients, with patients 49 years or younger diagnosed with AK being nearly 7 times more likely to be diagnosed with cSCC than those without AK. Other risk factors for cSCC besides AK included older age, White race (a proxy for skin type), a history of basal cell carcinoma, and male sex. The cumulative incidence of cSCC at 10 years reached 17.1% in patients with AK and 5.7% in control patients. The findings of this longitudinal cohort study can be used to develop recommendations for improving cSCC detection.