IL1RL1 and neoplasm: IL-33, in addition to being involved in proliferation, apparently when acting directly on the proliferating epithelial cells given their expression of ST2, is also capable of inducing M2 macrophage polarization and vigorous infiltration of eosinophils, perpetuating a chronic inflammatory state that is associated with progression towards a more advanced metaplasia [41,42], and of promoting angiogenesis and tumor cell proliferation [43].