[Ultrastructural study of 6 cases of ameloblastoma].

Three cases of simple ameloblastoma were studied by electron microscopy. The classical ultrastructural features of these tumors are analysed and compared with reports in the literature and the development of the enamel organ. The authors stress the presence of two cell types (light and dark) probably corresponding to different degrees of maturity. One case of cystic ameloblastoma and one of granular cell ameloblastoma are then reported. The nature of the inclusions in this latter tumour is probably mixed: lysomal and secretory, perhaps ameloblastic. Finally, a malignant ameloblastoma is described under electron microscopy, for the first time. Closely related to simple ameloblastomas, it may be distinguished only by the presence of signs of cellular degeneration and numerous mitoses, sometimes abnormal.