Combination of Binary System with Ki67 Immunohistochemical Staining: a Reliable Grading Method for Oral Epithelial Dysplasia

Statement of the Problem: Oral epithelial dysplasia (OED) is a common potentially malignant lesion of oral cavity that should be managed to prevent likely malignant transformation.Purpose: Here, we present a combination of binary grading system with complementary immunohistochemical (IHC) staining for Ki67 biomarker to provide a reproducible OED grading system.Materials and Method: In this crosssectional study, seventy out of one hundred OED specimens, which were accompanied by IHC stained microscopic slides for Ki67 antigen were evaluated by four independent oral pathologists. Both threetier and binary grading systems based on WHO microscopic criteria were employed , blindly in a fourstep method with at least twoweek interval between each observation. Intra and interobservational reliability was assessed using Kappa statistical analysis.Results: OED diagnosis based on binary system showed significant intraobserver reliability comparing to threetier system without biomarker. Moreover, OED diagnosis based on binary system using Ki67 biomarker showed significant interobserver reliability comparing to diagnosis in three tier system and based on binary system without Ki67 biomarker showed significant interobserver reliability comparing to diagnosis based on threetier system without Ki67.Conclusion: Here, we found that application of IHC staining for Ki67 biomarker in binary system might provide a more reliable grading method for oral pathologist form different educational background.