Giant-cell tumour of bone: cytological studies.

Cell-surface markers were investigated in 7 patients with giant-cell tumours and 30 patients with other tumours as controls. 25--55% of mononuclear cells in giant-cell tumours showed immunoglobulin-mediated phagocytosis. These phagocytic cells showed rapid adherence, trypsin resistance and potent nonspecific esterase activity. Thus, giant-cell tumours contained considerable numbers of macrophages with typical characteristics and functions. Macrophages did not proliferate in cultures of giant-cell tumours, whereas the non-adherent cells did. Further, established cell lines from these tumours consisted of spindle-shaped cells without surface markers or the ability to phagocytose or display nonspecific esterase activity. We consider that macrophages, which may be precursors of giant cells in giant-cell tumours, are non-malignant cells of host origin rather than tumour cells acquiring some properties of macrophages. We found that macrophages were more abundant in giant-cell tumours than in other tumours of mesenchymal origin, but any effect of their presence on the clinical behaviour and prognosis of the tumour remains highly speculative.