Osteoclasts are present in the giant cell variant of malignant fibrous histiocytoma.

We assessed the osteoclast-like giant cells in a giant cell-rich variant of malignant fibrous histiocytoma (MFH) for characteristics which are specific for osteoclasts, including excavation of bone and binding of osteoclast-specific monoclonal antibodies. Excavations characteristic of osteoclastic activity were found when the bone slices were inspected in the scanning electron microscope after incubation. Two monoclonal antibodies which bind specifically to osteoclasts showed strong membrane reactivity. These results provide strong evidence for the osteoclastic nature of the giant cells in this variant of the MFH. Osteoblasts are known to control the function of the osteoclast, and since there is bone formation present in at least half of the giant cell-rich variant of MFH it may be that it is the cells with properties peculiar to osteoblasts within the tumour which are responsible for the recruitment of the osteoclasts.