الفهرس 
material and methodsOnly 14 pages are availabe for public view
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Abstract
Giant cell lesions in the oral tissues occur as extrabony lesions in the soft tissues and intraosseous growths within the jaws. The present study was carried out to determine both the vascular changes and possible histogenesis of the giant cell lesions by using factor VIII related antigen for detection of the possible endothelial cell origin immunohistochemically. Moreover monoclonal antibody MB1 was used for detection of possible osteoclastic origin among these lesions . The current study was conducted on thirty patients complaining of PGCG, CGCG and GCT. These patients were subjected to complete clinical and radiographic examination . Two groups were identified from the bony lesions : nonaggressive group and aggressive group. Biopsies were taken from the lesions and stained with haematoxylin & eosin ( for histological examination and diagnosis) and factor VIII & MB1 immunohistochemical staining. Statistically GCT cases revealed higher mean values than that of the studied aggressive CGCG cases. The differences showed mild statistical significance as regard to mean number of MNGCs, nuclei inside these cells, lymphocytes, blood vessels and stromal mononuclear cells. The histogenesis of the MNGCs showed to be of osteoclastic origin (positive to MB1 immunohistochemical staining). Conclusioins 1The increased number of mitotic figures of the stromal mononuclear cells, number of lymphocytic infiltration and number of blood vessels were directly related to the aggressiveness . 2 GCT of the jaw is likely to be biologically distinct from the aggressive giant cell lesions as it showed significant clinicopathological features of higher grade of aggressiveness . 3The histogenesis of the MNGCs in the giant cell lesions were clarified in the current study to be of osteoclastic nature being positive to the monoclonal antibody MB1, while the endothelial origin is excluded as they were negative to factor VIIIrelated antigen . 4The positive reactivity of the mononuclear stromal cells to the monoclonal antibody MB1 might point to these cells as proosteoclast progenitors. Consequently the union of these progenitor cells might be a possible mechanism of MNGCs formation .