Clinical practice and pathology of oral potentially malignant disorders and oral epithelial dysplasia following the revision of the WHO Classification of Head and Neck Tumours （5th Edition）

Abstract

It is well known that the World Health Organization （WHO） Classification of Head and Neck Tumours is an essential tool and glossary for standardizing diagnostic practices worldwide. This report provides an overview of the revisions to the WHO Classification of Head and Neck Tumours （5th edition） regarding oral potentially malignant disorders and oral epithelial dysplasia related to superficial lesions among epithelial tumors in the oral cavity. In 2017, the fourth edition of the WHO Classification of Head and Neck Tumours described oral potentially malignant disorders for the first time. A major topic at that time was the integration of the concepts of previous precancerous conditions and precancerous lesions. In this revision, three disorders were deleted, one was incorporated into a familial cancer syndrome, and three new disorders were added: proliferative verrucous leukoplakia, oral lichenoid lesions, and oral graft-versus-host disease. Oral epithelial dysplasia is defined as a lesion with oral potentially malignant disorders and carries a risk of malignant transformation to squamous cell carcinoma. The grading of oral epithelial dysplasia has become a histopathological evaluation tool for potentially malignant disorders of the oral cavity. On the other hand, the revisions to oral epithelial dysplasia may be interpreted as contradictory. We outline the issues and the Oral Superficial Cancer Working Group’s thinking on oral epithelial dysplasia.