Histopathology of nonalcoholic fatty liver disease

Table 1 Grading activity and staging fibrosis in nonalcoholic steatohepatitis according to Brunt et al (adapted from[53,54])

	Steatosis (1: ≤ 33%, 2: 33%-66%, 3: ≥ 66%)	Ballooning (zonal location and severity recorded)	Inflammationa
			L-Lobular [(0-3): 0: absent, 1: < 2, 2: 2-4, 3: > 4 foci]	P-Portal [(0-3): 0: absent, 1: mild, 2: moderate, 3: severe]
Grade 1 (mild)	1-2	Minimal, zone 3	L = 1-2	P = 0-1
Grade 2 (moderate)	2-3	Present, zone 3	L = 1-2	P = 1-2
Grade 3 (severe)	2-3	Marked, predominantly zone 3	L = 3	P = 1-2

^aCounted in 20 × fields. Stage of fibrosis: 1: Zone 3 perisinusoidal fibrosis, focal or extensive; 2: As above with focal or extensive periportal fibrosis; 3: Bridging fibrosis; 4: Cirrhosis, probable or definite.

Table 2 Nonalcoholic steatohepatitis Clinical Research Network system for scoring activity and fibrosis in nonalcoholic fatty liver disease (modified from[54])

Steatosis grade (S)	Lobular inflammationa (L)	Hepatocyte ballooning (B)
0: < 5%	0: None	0: None
1: 5%-33%	1: < 2	1: Few ballooned cells
2: 34%-66%	2: 2-4	2: Many ballooned cells
3: > 66%	3: > 4

^aCounted in 20 × fields. Nonalcoholic fatty liver disease Activity Score: S + L + B (range 0-8). Stage of fibrosis (Fibrosis score): 0: None; 1: 1a, mild, zone 3 perisinusoidal fibrosis, 1b, moderate, zone 3 perisinusoidal fibrosis, 1c, portal/periportal fibrosis only; 2: Zone 3 perisinusoidal fibrosis and portal/periportal fibrosis; 3: Bridging fibrosis; 4: Cirrhosis, probable or definite.