Immunohistochemical study of mononuclear phagocyte antigens in giant cell tumor of bone.

The cytogenesis of giant cell tumor of bone (GCT) was assessed by immunohistochemical methods. Three GCT were analyzed by a sensitive immunoalkaline phosphatase technique with a panel of monoclonal antibodies, including eight reacting with separate antigens previously found to be present on mononuclear phagocytes (MPs) and one specific for the endothelial marker, coagulation Factor 8. Among the MP-associated antigens evaluated were leukocyte common antigen (LCA), HLA-DR, C3b receptor, and C3bi receptor. Also incorporated in the panel were antibodies to MP-associated antigens with well-characterized tissue distribution but of currently unknown function. Constituent cells of the tumors varied in their reactions with the antibodies of the panel. Although mononuclear cells in tumor stroma were labeled with all of the antibodies against the MP markers, giant cells reacted strongly only with antibodies to LCA and the MP-associated antigen recognized by the antibody EBM11. Giant cells were weakly and focally labeled with antibodies (KB90 and UCHM1) against two additional MP-associated determinants and were unreactive with the remaining antibodies in the panel. Spindled stromal cells, which appeared to produce collagen, were not labeled with any of the antibodies in the panel. Only endothelial cells reacted with antibody to Factor 8. The results of this study suggest that giant cells of GCT are derived from stromal cells of mononuclear phagocyte lineage, and that the stromal precurser cells lose some, but not all, MP-associated antigens as they mature into giant cells.