INTER-OBSERVER VARIABILITY AMONG PATHOLOGISTS IN THE INTERPRETATION OF LESIONS OF PROLIFERATIVE VERRUCOUS LEUKOPLAKIA SPECTRUM: A COLLABORATIVE PILOT STUDY

Objective The use of diverse terminology may lead to inconsistency in the diagnosis and subsequent treatment of lesions within the proliferative verrucous leukoplakia (PVL) spectrum. The objective of this study was to determine inter-observer variability between pathologists in the diagnosis of PVL spectrum lesions. Methods Digitally scanned slides of 40 PVL lesions of varying stages were diagnosed by six oral pathologists (OP) and six head and neck pathologists (HNP) at multiple institutions. Inter-observer agreement on diagnoses was evaluated by Fleiss’ kappa analysis using Microsoft Excel 2013 and IBM SPSS version 25 software. Results The responses provided were grouped into five broad categories. Category 1, simple hyperkeratosis with/without low-grade dysplasia; category 2, verrucous hyperplasia/keratosis with/without low-grade dysplasia; category 3, high-grade dysplasia or carcinoma-in-situ with/without verrucous surface change; category 4, verrucous carcinoma (VC) or atypical epithelial proliferation suggestive of but not fulfilling criteria of VC or squamous cell carcinoma (SCC) and; category 5, papillary or conventional SCC. The overall level of agreement between all pathologists for all cases as measured by Fleiss’ kappa (KF) was 0.270, considered fair agreement. Amongst OP the KF was 0.225, whereas amongst HNP the KF was 0.344. The best agreement between pathologists was on category 5 lesions (KF=0.650) followed by category 1 (KF=0.312). The least agreement was within categories 2 (KF=0.150), 3 (KF=0.192) and 4 (KF=0.156). Conclusion This study reflects the lack of standardized diagnostic criteria and terminology for lesions in the PVL spectrum. We recommend that standardized criteria and terminology be proposed and established by an expert panel position paper, which would assist pathologists and clinicians to uniformly diagnose and manage PVL spectrum lesions more effectively.