Fig. 1.

Osteoclastogenesis by giant-cell tumor is constituted of stromal cells (GCTSCs). A diagram representing pathophysiology of osteoclast-rich giant-cell tumor (GCT). A neoplastic component of GCT is mainly dysfunctional stromal cells. Mesenchymal stromal cell markers such as STRO-1 and SDF-1α are positive. Stromal cells produce sufficient chemokines and cytokines which recruit CXCR4 (+) osteoclast precursors from blood vessels and promote osteoclastogenesis. SDF: stromal cell-derived factor, MCP: monocyte chemoattractant protein, TNF: tumor necrosis factor, IL: interleukin, RANKL: receptor activator of nuclear factor kappa-B ligand, RANK: receptor activator of nuclear factor kappa, M-CSF: macrophage colony-stimulating factor.