Positive association between actinic keratosis and internal malignancies: a nationwide population-based cohort study.

Little is known about the comorbidities in actinic keratosis patients. To evaluate the association of actinic keratosis with certain malignancies. All patients with actinic keratosis (n = 61,438) and age- and sex-matched control subjects (n = 307,190) at a 5:1 ratio were enrolled using data from the Korean National Health Insurance Service between the years 2007 and 2014. In subjects with actinic keratosis, overall cancer incidence was higher than that for controls after income level, habitat, diabetes, hypertension, and dyslipidemia were adjusted (Hazard Ratio [HR] = 1.43 [95% confidence interval 1.38-1.47]). The positive association of specific cancers were observed in the following order: skin cancer (HR = 3.43 [2.47-4.75]), oral cavity and pharyngeal cancer (HR = 1.99 [1.57-2.52]), lymphoma (HR = 1.59 [1.28-1.96]), leukemia (HR = 1.35 [1.03-1.77]), prostate cancer (HR = 1.35 [1.21-1.51]), renal cancer (HR = 1.29 [1.02-1.63]), liver cancer (HR = 1.21 [1.09-1.35]), thyroid cancer (HR = 1.20 [1.05-1.38]), and gastric cancer (HR = 1.13 [1.03-1.23]). Although further research on pathologic mechanism is needed, the implications of a positive correlation between actinic keratosis and internal organ malignancies has great significance.