Oral epithelial dysplasia classification systems: predictive value, utility, weaknesses and scope for improvement

Abstract

At a workshop coordinated by the WHO Collaborating Centre for Oral Cancer and Precancer in the United Kingdom issues related to potentially malignant disorders of the oral cavity were discussed by an expert group. The consensus views of the Working Group are presented in a series of papers. In this report, we review the oral epithelial dysplasia classification systems. The three classification schemes [oral epithelial dysplasia scoring system, squamous intraepithelial neoplasia and Ljubljana classification] were presented and the Working Group recommended epithelial dysplasia grading for routine use. Although most oral pathologists possibly recognize and accept the criteria for grading epithelial dysplasia, firstly based on architectural features and then of cytology, there is great variability in their interpretation of the presence, degree and significance of the individual criteria. Several studies have shown great interexaminer and intraexaminer variability in the assessment of the presence or absence and the grade of oral epithelial dysplasia. The Working Group considered the two class classification (no⁄questionable⁄ mild -low risk; moderate or severe -implying high risk) and was of the view that reducing the number of choices from 3 to 2 may increase the likelihood of agreement between pathologists. The utility of this need to be tested in future studies. The variables that are likely to affect oral epithelial dysplasia scoring were discussed and are outlined here; these need to be researched in longitudinal studies to explore the biological significance of a low-risk or high-risk dysplasia.

Correlation Between Dysplasia and Ploidy Status in Oral Leukoplakia

“…The association between the grade of epithelial dysplasia and OSCC development is supported by several other studies [1,3,4,23]. It is important to note that patients with mild dysplasia may develop OSCC [9].…”

“…The haematoxylin and eosin-stained sections of all the cases were examined by two experienced oral pathologists for agreement on the diagnosis and grade of dysplasia. Grading of epithelial dysplasia was done according to the 2005 WHO classification of epithelial dysplasia [17] and was then further defined as low-risk or high-risk according to the workshop coordinated by the WHO Collaborating Centre for Oral Cancer and Precancer in 2005 [1]. Cases where there was disagreement on the histologic grading of the dysplasia, ulceration with extensive inflammation, or an inadequate amount of tissue for flow cytometric evaluation were excluded from the study.…”

“…The current best practice of care is to remove these lesions for histologic analysis. The presence of epithelial dysplasia, albeit with well-documented limitations, is still the gold standard in evaluating the malignant potential of suspicious lesions of the oral mucosa [1][2][3][4]. It is also well-documented that a number of PMDs, regardless of the presence of dysplasia, do not progress to carcinoma [5].…”

Current Views and Perspectives on Classification of Squamous Intraepithelial Lesions of the Head and Neck

“…However, due to frequent problems in providing reliable distinctions between the different grades, the Working Group considered a replacement of the four grades of DS with a two-grade DS, more applicable when reporting the presence or absence of epithelial dysplasia, such as: ''no/ questionable/mild''-low risk, and ''moderate or severe''-implying high risk. This reduction of the number of grades has been shown to have merit, with an improvement in kappa agreements, as previously presented by Kujan and co-workers [6,7,14]. The authors compared the interobserver agreement using the WHO-dysplasia system and the new binary grading system.…”

“…Preference depends on a pathologist's training, bias and local custom [5]. Numerous articles have reported attempts to evaluate the reliability and inter-observer agreement of these grading systems for oral and laryngeal SILs [6][7][8][9][10][11][12][13]. Some of them have also compared WHO grading systems with new proposals, such as a binary grading system and other classifications for oral lesions or, more widely, for the whole head and neck region (Table 1) [2,7,9,[15][16][17].…”