Calcifying odontogenic cyst: report of two cases and review of literature.

The "Histological Typing of Odontogenic Tumours" (W.H.O., 1992) classified the Calcifying Odontogenic Cyst (C.O.C.) into two variants: the non-neoplastic cystic C.O.C. and the odontogenic ghost cell tumour, which is predominantly solid. We reported two cases of C.O.C.: a case with intraosseous development and another with extraosseous localisation, in the soft tissue of the alveolar area. The first case represents a cyst delimited by a squamous, non-keratinized epithelium, thickened in some areas through the accumulation of ghost cells (big pale-staining cells with a non-staining nuclear area). The connective tissue wall contains small ameloblastoma like islands. Dysplastic dentine islands, adjacente to the basal layer of the epithelium or in the connective tissue wall were also observed. The second case was a well-delimitated tumour consisting of ameloblastoma-like islands with numerous ghost cells inside. Islands of dysplastic dentine with psammomathous calcifications also exist. In certain histological sections microcystic aspects surrounded by ghost cells, dentinoid and ameloblastoma-like structures were noticed. The histochemical reaction for keratin and the immunohistochemical reaction for epithelial membrane antigen and for citokeratin were positive for ghost cells, suggesting their epithelial origin. Through this article we try to render pathologists sensitive with a particular and rare maxillary tumour.