The pathogenesis of secondary CLS due to anti-cancer treatment is not well-known, but there are several studies supporting the role of pathogenic molecules of idiopathic CLS including multiple cytokines, angiopoietin-2, and vascular endothelial growth factor (VEGF) [5,10,79,80], although the pathophysiology of idiopathic and secondary CLS may be somewhat different, because CLS by anti-cancer drugs could also develop due to a direct toxicity to the capillary system. This evidence concerns the gene ANGPT2 and capillary leak syndrome.