Table 1.

Comparison of grading systems for LD, after WHO 2017 [8], 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 [61]	SIN classification  [60]	Ljubljana classification [59]	Amended Ljubljana classification [58]	WHO 2017 [8]
	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

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

SIN  squamous intraepithelial neoplasia, SIL  intraepithelial lesion