[Hairy tongue and hairy oral leukoplakia--a differential histopathologic diagnosis].

10 specimens taken from oral hairy leukoplakia were compared to 8 histological preparations from hairy tongue. We found 9 criteria helpful concerning the histopathologic differential diagnosis of these entities. Oral hairy leukoplakia shows a gently papillated surface, a prominent horny layer with confluent bacterial overgrowth, and ballooned epithelial cells with a distinct perinuclear halo in a bandlike arrangement. Hairy tongue, in contrast, grows exophytically with a digitiform surface, the horny layer is rather thin, and the microorganisms are confined to the ends of the digitations; the ballooned epithelial cells show pale cytoplasm. Considering the growing incidents of HIV infection, the dermatologist should be familiar with the characteristics of oral hairy leukoplakia and its histopathological differential diagnosis.