Electron microscopic studies of fibrous dysplasia.

Very few ultrastructural studies of fibrous dysplasia have been reported up to date. Eight cases of fibrous dysplasia (six cases of monostotic and two cases of polyostotic disease) were studied in detail by an electron microscope, and were compared with desmoplastic fibroma and fibrous cortical defect in order to clarify the fine structure of this disease. The fine structure of osteoblast or osteocyte-like cells, large cells including collagen fibers in the cytoplasm and so on was newly observed in this study. It was impossible to distinguish between monostotic and polyostotic forms even through an electron microscope.