Histopathology of nonalcoholic fatty liver disease/nonalcoholic steatohepatitis

Table 2 Grading and staging system for nonalcoholic steatohepatitis[13]

Grading and staging
Grading
Grade 1 (mild)	Steatosis: up to 66%
	Ballooning: occasional in zone 3
	Intralobular inflammation: scattered polymorphs ± lymphocytes
	Portal inflammation: no or mild
Grade 2 (moderate)	Steatosis: any degree
	Ballooning: obvious, predominantly zone 3
	Intralobular inflammation: polymorphs and chronic inflammation noted
	Portal inflammation: mild to moderate
Grade 3 (severe)	Steatosis: panacinar
	Ballooning: ballooning and disarray obvious, predominantly in zone 3
	Intralobular inflammation: scattered polymorphs ± mild chronic inflammation
	Portal inflammation: mild or moderate
Staging
Stage 1	Zone 3 perisinusoidal/pericellular fibrosis, focal or extensive
Stage 2	Zone 3 perisinusoidal/pericellular fibrosis + focal or extensive periportal fibrosis
Stage 3	Zone 3 perisinusoidal/pericellular fibrosis + portal fibrosis + bridging fibrosis
Stage 4	Cirrhosis