Yun SJ, Bae JM, Kim H, et al. - Researchers carried out a nationwide retrospective cohort study to evaluate the risk of internal malignancy in non-melanoma skin cancers (NMSC) patients (n = 27,259) vs controls without NMSC (n = 54,518) in the Korean population. From January 2007 to December 2016, the Korean national health insurance database were used. For the NMSC patients and controls, respectively, the overall risk of an internal malignancy at all sites was 2727.7 and 1392.4 per 100,000 person-years. In patients with NMSC, the risk was significantly higher. The highest risk of bone cancer was followed by nasal cavity and larynx, oral cavity and pharynx, anus and anal canal, and cervical cancers with risks greater than fivefold higher in NMSC patients compared with the controls. The NMSC patients also had statistically higher risks of thorax, esophagus, breast, lung, stomach, thyroid gland, and non-Hodgkin's lymphoma. On the other hand, the risks of colon and rectum cancers in NMSC patients were found to be significantly decreased. Findings suggested that NMSC patients need thorough screening and follow-up for internal malignancy.