The potential sources of these damage-induced Lgr5+ stem cells include Lgr5− progenitor cells from the noninjured liver23, recruitment from distant sites (e.g., mesenchymal cells)24, Axin2+ hepatocytes surrounding the central vein25, Sox9+ hybrid periportal hepatocytes around the portal vein and biliary tree26, or transdifferentiation of hepatocytes into ductal cells, as that occurs in tumors of the biliary tree (intrahepatic cholangiocarcinoma)27. The gene discussed is SOX9; the disease is biliary tract neoplasm.