Macrophages in giant cell tumours of bone

Abstract

Five giant cell tumors of bone were studied to determine the degree of macrophage infiltration and whether the giant cells expressed the characteristics commonly associated with macrophages, i.e., Ig[immunoglobulin]G Fc and C3 [3rd complement component] receptors, phagocytosis and non-specific esterase activity. Macrophages were assessed in trypsin-derived tumor cell suspensions by IgG EAC [erythrocyte, antibody, complement] rosette formation and in frozen sections of tumor by EA adsorption. The percentage of macrophages in cell suspensions from 4 of the tumors ranged from 11-40%. Strong EA adsorption occurred over 35-95% of the tumors'' surface and significant non-specific esterase positivity was observed in the tumor sections. The giant cells were receptor negative and non-phagocytic, but a low percentage of them expressed esterase activity. Despite the fact that large numbers of macrophages were present in the tumors, the giant cells were probably derived from cells other than macrophages.