Consensus in Diagnosis and Classification of Oral Epithelial Dysplasia: A Comparative Analysis of H&E-Stained Sections with and without p53/p16 Immunohistochemistry

Introduction

WHO grading of oral epithelial dysplasia (OED) is employed by pathologists to aid in prognostication and treatment planning. However, considerable inter-observer variability exists. Recently, p53 abnormal OED has been proposed as a unique entity with an increased risk of malignant transformation. Subsequently, a pattern-based approach to p53/p16 immunohistochemistry (IHC) interpretation has been developed to classify OED into Human Papillomavirus (HPV)-associated, p53 wild-type (conventional), and p53 abnormal OED. In this study, the grading (three-tiered and two-tiered) and classification of OED were compared using hematoxylin and eosin-stained sections (H&E) with and without p53/p16 IHC.

Materials and Methods

Formalin-fixed, paraffin-embedded oral biopsy specimens with targeted Next-Generation Sequencing results and/or high-risk HPV in situ hybridization results were collected from 51 patients. Inter-observer variability among 18 pathologists was determined using Fleiss’ kappa (κ).

Results

93% of HPV-associated OED and 77% of p53 abnormal OED were successfully identified using p53/p16 IHC. In contrast, 55% of HPV-associated OED and 37% of p53 abnormal OED were identified using H&E. 19% of p53 abnormal OED were initially interpreted as “reactive, no dysplasia” using H&E; this decreased to 10% following reviewing of p53/p16 IHC. There is excellent agreement beyond chance and fair to good agreement beyond chance for the classification of OED using p53/p16 IHC (overall, κ = 0.61, HPV-associated OED, κ = 0.92; p53 abnormal OED, κ = 0.56). Both the three-tiered and two-tiered dysplasia grading systems demonstrate poor agreement beyond chance in H&E (κ = 0.35 and 0.39; p < 0.0001) and p53/p16 IHC (κ = 0.33 and 0.37; p < 0.0001).

Conclusions

A panel of p53/p16 IHC can improve both diagnostic accuracy and inter-observer agreement in the diagnosis of OED. p53 abnormal OED cannot be reliably identified on H&E alone, and the histologic spectrum of HPV-associated dysplasia is broader than currently appreciated.