Table 1.

Comparison of grading systems for LD, after WHO 2017 [20], with corrected levels. The published version limits low-grade dysplasia to the lower third, rather than the lower half of the epithelium

Level of abnormal maturation (WHO 2005)	WHO 2005 Classification [34]	SIN Classification [35]	Ljubljana Classification [33]	Amended Ljubljana classification [19]	WHO 2017 [20]
	Squamous hyperplasia	Squamous hyperplasia	Squamous hyperplasia	Low grade SIL	Low grade dysplasia
Lower 1/3	Mild dysplasia	SIN 1	Basal/parabasal hyperplasia
1/3 to 1/2	Moderate dysplasia	SIN 1 or 2	Atypical hyperplasia	High grade SIL
Upper 1/2–3/4		SIN 2			High grade dysplasia *
Full thickness	Severe dysplasia
	Carcinoma in situ		Carcinoma in situ	Carcinoma in situ

SIN squamous intraepithelial neoplasia, SIL intraepithelial lesion

^*A grade of carcinoma in situ may be used if a three-tiered system is preferred