This nationwide population-based retrospective cohort study of the association between JIA by their treatment allocation and cancer risk with up to 8 years follow-up reveals that this East Asian children population with JIA is associated with a 3-fold increased risk of malignancy (IRR = 3.21 and adjusted HR = 3.14) and there is no statistically significant increased risk in these patients with exposure to methotrexate and/or TNF inhibitors. This evidence concerns the gene TNF and cancer.