Diagnosis is usually made on the clinical appearance without the need for a tissue biopsy. However, when biopsies have been taken, the histologic appearance is one of marked elongation and hyperparakeratosis of the filiform papillae and numerous bacteria growing on the epithelial surface.<unk>  tongue may be confused with<unk>  leukoplakia, however the latter usually occurs on the sides of the tongue and is associated with an opportunistic infection with Epstein–Barr virus on a<unk> ground immunocompromise (almost always human immunodeficiency virus infection but rarely other conditions which suppress the immune system). Classification<unk>  tongue (lingua villosa) refers to a marked accumulation of keratin on the filiform papillae on the dorsal surface of the tongue, giving a<unk> like appearance.<unk>  tongue (lingua nigra) refers to a<unk>  discoloration of the tongue, which may or may not be associated with<unk>  tongue. However, the elongated papillae of<unk>  tongue usually develop discoloration due to growth of pigment producing bacteria and staining from food. Hence the term<unk> , although<unk>  tongue may also be discolored yellow or brown. Transient, surface discoloration that is not associated with<unk>  tongue can be brushed off. Drug-induced<unk>  specifically refers to BHT that develops because of medication.
Black hairy tongue
Crenated tongue
Fissured tongue
Caviar tongue
Omphalolith
Perryville Tree engravings
Macrodontia 
Chattering teeth