Immunohistochemical evaluation of giant cell tumor of bone

Twenty seven cases of giant cell tumor of bone were evaluated for their cell kinetics by using proliferating cell nuclear antigen (PCNA) immunoreactivity and antiproteolytic and lysozymal activities in multinucleated giant cells and mononuclear cells in order to evaluate their cellular characteristics and possible histogenesis. The multinucleated giant cell nuclei were unlabeled by PCNA and the major proliferating cells in the tumor were identified as mononuclear cells. No significant correlation existed between the PCNA labeling index and histopathological gradings of the giant cell tumors. Mononuclear cells were either fibroblast-like cells or histiocyte-like cells. The fibroblastlike cells showed an intense immunoreactivity for vimentin and PCNA whereas the histiocyte-like cells were intensely reactive for lysozyme, alpha-1 antitrypsin, alpha-1 antichymotrypsin. The multinucleated giant cells, on the other hand, more frequently showed immunoreactivity of lysozyme, alpha-1 antitrypsin, alpha-1 antichymotrypsin mimicing the profile of histiocyte-like cells. The results of the present study allowed us to reasonably conclude that the fibroblast-like cells were the major proliferating cells in the giant cell tumors which may originate from the mesenchymal fibroblasts; the multinucleated giant cells do not form a proliferating population of cells but may be a fusion product of histiocyte-like cells possibly derived from the mononuclear phagocyte system. The conventional histopathological grading of the giant cell tumors of bone do not correspond with the cell proliferation potential in the tumor as assessed by PCNA immunohistochemistry.