Pathology of fatty liver: differential diagnosis of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) has emerged as a worldwide epidemic in the 21st century. The spectrum of its histopathology ranges from simple steatosis to steatohepatitis, with risk for progressive fibrosis that may lead to cirrhosis and hepatocellular carcinoma. This review is an update of the histopathology of NAFLD and its differential diagnosis, in particular alcoholic liver disease (ALD), encountered by practising pathologists. It also discusses the pathology of NAFLD in various ‘non-traditional’ settings: in children, after therapeutic intervention, and with concomitant liver diseases. The current grading and staging systems of NAFLD and ALD are also discussed.