Osteoclast Origin of Giant Cells in Giant Cell Tumors of Bone: Ultrastructural and Cytochemical Study of Six Cases

To clarify the histogenesis of giant cells appearing in giant cell tumors of bone (GCTB), an ultrastructural and cytochemical study of six cases was performed with both acid phosphatase (ACPase) and tartrate-resistant acid phosphatase (TRACPase) as marker enzymes. TRACPase is considered a specific marker for osteoclasts. ACPase was demonstrated in the macrophagelike stromal cells, the multinucleated giant cells, and the infiltrating macrophages. The enzyme reaction was localized in lysosomal dense bodies and Golgi areas. Intense TRACPase activity was demonstrated in the multinucleated giant cells, whereas a weak reaction was found in the macrophagelike stromal cells. The multinucleated giant cells and macrophagelike stromal cells resembled osteoclasts with regard to the subcellular localization of TRACPase. The present results suggest that the giant cells in GCTB are indeed derived from osteoclasts.