Diagnostic Studies. Radiographs reveal a large radiolucent lesion surrounded by a distinct margin of reactive bone. Cortical thinning, endosteal erosion, and trabecularization, or bony septation, of the cavity are associated findings. CT or MRI discloses the extent of involvement and bony margination. Lesions extend to with 1.5 cm of the adjacent joint space and articular cartilage. A chest radiograph should be performed in all patients with giant cell tumor to rule out metastases.

Gross examination reveals a soft, friable, reddish brown neoplastic tissue with the consistency of a wet sponge. Some areas are gelatinous or fatty, and some are aneurysmal and cavitated. Histologic features include multinucleated giant cells, a proliferative stroma with vesiculated nuclei, areas of aneurysmal tissue, areas of necrosis, reactive peripheral bone, and occasional mitotic figures and intravascular tumor plugs in venous sinuses.

Treatment. The size and stage of the tumor determine the type of treatment. For stage 1 or 2 lesions, curettage is often combined with bone grafting or cementation. Giant cell tumors of bone have a recurrence rate between 5% and 30%; Cementation and adjuvant treatment with phenol or liquid nitrogen may decrease the recurrence rate. For recurrent lesions or articular destruction, extensive joint reconstruction or joint replacement may be required.