Canals of Hering: recent insights and current knowledge.

The canals of Hering (CoH) begin in the lobules, are lined partially by cholangiocytes and partly by hepatocytes, and conduct bile from bile canaliculi to terminal bile ducts in portal tracts. They are not readily apparent on routine histological staining but are highlighted by the biliary cytokeratins CK19 and CK7. There is on average 1 CoH per 10 microm of bile duct length. The canals represent the true hepatocytic-biliary interface that thus lies within the lobule and not at the limiting plate. The CoH are destroyed early in primary biliary cirrhosis, perhaps explaining lobular "hepatitis" in this disease. They may also be the primary sites of scarring in methotrexate toxicity. Most intriguingly, the CoH have been speculated to harbor intraorgan stem cells of the liver, perhaps forming the hepatic stem cell "niche" and have been demonstrated to proliferate in disease states.