Giant cell tumor of bone

A rare bone sarcoma characterized by a usually benign space-occupying lesion, which is nevertheless locally aggressive and massively damaging to surrounding bone tissue. The tumor is composed of giant multinucleated cells (osteoclast-like cells), mononuclear macrophages, and mononuclear stromal cells which secrete pro-myeloid and pro-osteoclastic factors. Metastasis and malignant transformation are rare, but the recurrence rate is high.