Hairy leukoplakia–a histological study

Hairy leukoplakia is a recently described oral mucosal condition seen in immunosuppressed individuals, usually in association with HIV infection, when it is thought to be a sign of decreasing immunocompetence. It probably results from reactivation of infection by Epstein‐Barr virus (EBV) and usually presents as bilateral white patches on the lateral borders of the tongue. From a histological study of 20 cases we have found that the typical appearance of hairy leukoplakia is of acanthotic, hyperparakeratinized epithelium with Candida hyphae sometimes present in the parakeratin. A band of EBV infected, koilocyte‐like cells is present in the upper part of the prickle cell layers, these cells being swollen and pale staining, with prominent cell borders and perinuclear vacuoles. There is a paucity of inflammation in both the epithelium and lamina propria. An atypical appearance shows the koilocyte‐like cells lying isolated or in small groups, irregularly arranged in the prickle cell layer and without a hyperparakeratinized surface. Diagnosis of hairy leukoplakia should normally be confirmed by demonstrating EBV in the koilocyte‐like cells by immunocytochemistry or DNA in situ hybridization.