Current status and agenda in the diagnosis of nonalcoholic steatohepatitis in Japan

Table 1 The pathological criteria for the diagnosis of nonalcoholic fatty liver disease

Matteoni’s classification[45]
Type	Histological findings	Liver related deaths (mean observation period)		Diagnosis
		8.17 years[31]	18.5 years[32]
Type 1	Fatty liver alone	1.70%	2.70%	non-NASH
Type 2	Fat accumulation and lobular inflammation
Type 3	Fat accumulation and ballooning degeneration	11.00%	17.50%	NASH
Type 4	Type 3 and either Mallory-Denk body or fibrosis
NAFLD activity score (NAS)[47]
Item	Definition		Score	Diagnosis
Steatosis	< 5%		0	Total score
	5%-33%		1	0-2: non-NASH
	> 33%-66%		2	3-4: borderline
	> 66%		3	5-8: NASH
Lobular inflammation	No foci		0
	< 2 foci per 200 × field		1
	2-4 foci per 200 × field		2
	> 4 foci per 200 × field		3
Ballooning	None		0
	Few balloon cells		1
	Many cells/prominent ballooning		2

NAFLD: nonalcoholic fatty liver disease; NASH: nonalcoholic steatohepatitis.