Giant cell tumors are considered benign, however, they do rarely metastasize to the lungs and can be multicentric. They have a high potential for local recurrence when treated solely with a curettage. Characteristically they affect the articular ends of bone and may be associated with aneurysmal bone cysts.

CT is useful for demonstrating the absence of mineralization and for showing internal trabeculations as well as a subtle periosteal reaction. Campanacci et al. classified GCTs into three types based on their biological behavior, radiographic appearance, and degree of bone destruction:

• type I are considered latent with small intraosseous lesions
• type II are active and radiographically larger, with intact periosteum
• type III is aggressive and extends throughout the periosteum and surrounding tissues

Sarcomatous degeneration of giant cell tumors (GCT) occurs rarely and most of them are GCT previously treated with radiotherapy. The sarcomatous degeneration always has as a result high-grade sarcomas, with a high tendency to hematogenous dissemination.