Value of immunohistochemical detection of noncollagenous proteins of bone for the diagnosis of bone tumours.

The expression of osteonectin, osteopontin, bone sialoprotein, and osteocalcin was evaluated by immunohistochemistry in 57 cases of osteoid-forming and non-osteoid-forming bone tumours using specific polyclonal antibodies and the avidin-biotin peroxidase complex method. A positive immunostaining was found in all of the osteoid-forming rumours (osteoblastoma and osteosarcoma), both in the cells and in the extracellular matrix. Among non-osteoid-forming tumours, immunoreactivity to noncollagenous proteins was present in the cells but not in the matrix of chondrosarcoma, malignant fibrous histiocytoma, and fibrosarcoma, as well as in the mononuclear component of giant-cell rumours. Contrary to small-cell osteosarcoma, Ewing's sarcoma was always negative for all of the noncollagenous proteins considered. These results suggest that the immunohistochemical evaluation of noncollagenous proteins of bone may be a useful tool for the differential diagnosis of bone neoplasms, particularly among the heterogeneous group of small round cell tumours.