[The expression of various cytokeratins by epithelial cells of calcified odontogenic cysts].

The calcifying odontogenic cyst (COC) is a rare lesion without specific clinical characteristics. Its diagnosis is essentially histopathological showing the presence of ghost cells associated with narrow squamous epithelium, the basal strata of which consist of clearly delineated cells differentiating in areas of the stellate reticulum in a similar way to ameloblastoma. The results of ultrastructural observations of the ghost cells as well as histochemical and immunohistochemical studies suggest that they are the sites of abnormal keratinisation. The aim of this study of one COC mas to locate the stages in epithelial maturation associated with the formation of ghost cells. Six monoclonal antibodies were used; three with a wide spectrum (KL1, AE3, AE1), two with a narrow spectrum against high molecular weight cytokeratins (AE2, AE8) and one against vimentin (M725). Histopathological examination of the COC revealed three different types of cells in the epithelial lining and the epithelial islands; small basal cubic cells surrounding larger ones placed centrally or suprabasally; balloon shaped cells or flattened ghost cells rolled up on themselves to resemble keratinising pearls, or cornifying cells. The ghost cells and cornifying cells had an altered distribution of their cytokeratins demonstrated by the absence of staining of antibodies against cytokeratins. The differentiated cells adjacent to them showed cytokeratins typical of squamous epithelium rather than those associated with the process of keratinization. The coexistence of cornifying and ghost cells testifies to the great potential of odontogenic epithelium to form numerous epithelial islands.