Each cancer type is presented according to the following scheme: (1) short introduction to the specific cancer type; (2) net effect of IL-33/ST2 signaling for tumorigenesis; (3) origin of IL-33- and ST2-expressing cells in the tumor stroma of a particular cancer type; (4) mechanisms of action of IL-33; and (5) therapeutic opportunities. Here, IL1RL1 is linked to neoplasm.