TRANSFORMING GROWTH-FACTOR-ALPHA AND CD68 IMMUNOREACTIVITY IN GIANT-CELL TUMORS OF BONE - A STUDY ON THE NATURE OF STROMAL AND GIANT-CELLS,AND THEIR INTERRELATIONS

To clarify the nature of neoplastic cells, 17 giant cell tumours of bo ne were studied histologically and immunohistochemically. L1 antigen a nd S-100 protein were not detected in the tumour giant cells and strom al cells, although present in non-neoplastic macrophages. The giant ce lls in all the lesions, some stromal cells, and osteoclasts in the nor mal bone showed CD68 and transforming growth factor alpha (TGFalpha) i mmunoreactivity. Fibrohistiocytic antigen, factor XIIIa, was expressed in large numbers of stromal cells in all lesions. Some stromal cells expressed alpha-smooth muscle actin and osteocalcin. These immunohisto chemical results suggested that the stromal cells of giant cell tumour s of bone showed histiocytic and occasional myofibroblastic and osteob lastic differentiation. Proliferating cell nuclear antigen was demonst rated in the nuclei of the stromal cells only, indicating that these w ere the sole proliferating elements. TGFalpha produced by the giant ce lls and some stromal cells may play a role as a mediator for the attra ction and/or proliferation of the precursor cells, and may suppress th e activity of osteoblastic stromal cells, resulting in restricted bone formation in giant cell tumours.