Some lesions on the tongue include the white patches that are characteristic of leukoplakia and the cottage-cheese-like patches that are characteristic of thrush, according to WebMD. Oral lichen planus produces lesions that resemble lacy white lines on the tongue.
In leukoplakia, the cells on the tongue grow too quickly and so build up into white patches, according to WebMD. Though it's benign, it can increase a person's risk of oral cancer and should be treated by a dentist. Thrush is a yeast infection that strikes people whose immune systems are weakened. Medical professionals do not know what causes lichen planus, and it often goes away without treatment.
The lesions of geographic tongue or migratory glossitis are characterized by patches arranged in a way that remind people of a map, says Mayo Clinic. This is because the tongue is missing papillae. Moreover, when the lesions heal in one area of the tongue they migrate to a different area. Geographic tongue is harmless.
Black hairy tongue is also a benign condition, according to the National Institutes of Health. It is characterized by enlarged and elongated papillae that make the tongue seem carpeted. The papillae may be black, but can also be green, blue, yellow, brown or have no pigment at all. Black hairy tongue usually goes away on its own.