FGF18 and neoplasm: FGF18 plays a key role in regulating the biological activity of tumor cells and immediately surrounding tissue cells of the tumor microenvironment via multiple signaling pathways (Shimokawa et al., 2003; Sonvilla et al., 2008; Gauglhofer et al., 2011; Zhang et al., 2019a; Zhang et al., 2019b; Jomrich et al., 2019).