FIG. 1.

Stages of fibrosis in NAFLD according to the NASH CRN staging system (Masson trichrome stains). Collagen is blue with this method. Stage 1 (left): centrilobular perisinusoidal fibrosis. Blue stained collagen fibers outline the sinusoids surrounding the central vein in the center of the field. Stage 2 (left middle): centrilobular perisinusoidal fibrosis and periportal fibrosis. Delicate collagen fibers are deposited around the sinusoids in the upper part of the field while denser collagen expands the portal tract in the lower part of the field. Stage 3 (right middle): bridging fibrosis. A vascularized septum of fibrous tissue transects the hepatic parenchyma. Stage 4 (right): cirrhosis. Nodules of hepatocytes are surrounded by variable-size fibrous septa.