A case of osseous choristoma of the tongue in a 27-year old man is described. The lesion appeared as a pedunculated mass measured about 1.0 by 1.0cm, on the dorsal surface of the left posterior third of the tongue. The patient stated that the lesion had been present for about twenty years. The mass was excised under general anesthesia. Rentogenogram of the excised material revealed a well-circumscribed radiopaque nodule within the mass. Histologically the lesion consisted of a well-circumscribedmass of dense lamellar bone. Haversian canals were seen, as well as osteocytes in the lacunae. The bony mass was surrounded by dense fibrous connective tissue with stratified squamous epithelium of the lingual surface. The ulcer formation was partially observed in the overlying epithelium with seconday inflammatory changes. There have been very few reports of the osseous choristomas in the oral region. To date, Thirty-six cases have been reported in the world literature. The present report is the fourth case in Japan.
