Osseous choristoma of oral cavity--report of two cases and review of the literature. 
Osseous choristoma of the oral cavity is an extremely rare lesion.  Two cases of osseous choristomas of oral cavity, representing two different natures of such lesions are reported.  One was situated on the dorsal surface of posterior tongue just anterior to the circumvallate papillae and the other on the right buccal mucosa just below the orifice of the Stensen's duct.  To date, about 73 cases of oral osseous choristoma have been reported in the literature including the two present cases, of which, 61 and 8 cases occurred in the tongue and buccal mucosa, respectively.  The clinical and microscopic characteristics, and their common sites of these peculiar lesions are presented.  The origin and pathogenesis of the lesion are discussed and the literature on the subject is reviewed.