LGR5 and cyst: Lgr5, a member of the Wnt signaling pathway, has been identified as a new molecular marker of stem cells in endoderm-derived organs including the small intestine, colon, stomach, liver, and pancreas.3–8 The 3D culture system known as organoid culture allows long-term expansion of Lgr5-positive stem cells into cyst-like structures (organoids) with properties resembling those of the original tissues.