Giant cell tumor of bone (GCT) and aneurysmal bone cyst (ABC) are common benign aggressive bone tumors or aneurysmal lesions in clinical practice. Although they are generally benign lesions of bone, these diseases also have the potential to develop malignancy, distant metastases, and eventually undergo amputation or even life-threatening conditions. Therefore, early detection and diagnosis, and selection of appropriate treatment according to the stage of the disease are particularly important. Clinical manifestations Taking GCT of limbs as an example, the main symptoms are pain, mostly mild to moderate pain, joint function limitation and joint effusion, and pathological fracture may occur in a few patients; there may be swelling at the lesion site, and local soft tissue masses may be found if the bone lesion penetrates the bone cortex and protrudes into the soft tissue, and sometimes the masses increase rapidly, mostly due to tumor bleeding; there may be increased local skin temperature and venous filling, etc. Diagnosis and differentiation Based on the clinical manifestations and imaging data, the preliminary diagnosis of GCT and ABC can be made. (ABC presents as a distending osteolytic lesion in the proximal epiphysis, which is sometimes difficult to differentiate from GCT or TOS (highly malignant osteosarcoma) on imaging and requires tissue biopsy pathology for a definitive diagnosis. X-ray of GCT of the distal right femur, showing eccentric, osteolytic expansile growth lesions Tumor staging According to Enneking’s bone tumor staging and Campanacci’s imaging staging, GCT and ABC, etc. can be divided into 3 stages. Stage 1 (G0T0M0) The stationary stage or latent stage generally has no clinical symptoms; X-ray shows complete or slightly thinned bone cortex, complete boundary of osteolysis area, and mild bone hypertrophy around the tumor. The tumor is usually not large and does not extend to the articular cartilage. The pathological changes are benign. Stage 2 (G0T0M0) There are clinical symptoms in the active stage, obvious X-ray performance, the lesion is distended, but the bone cortex is not destroyed, the pathological changes are benign. Stage 3 (G1T1～2M0～1) Aggressive with clinical symptoms, obvious X-ray performance, aggressive lesions with bone cortical defects, with soft tissue masses, lesions may extend to subchondral bone, or even invade the joint. Pathological changes are benign or malignant. Treatment Surgery is the most effective method. The ideal surgery is to completely remove the tumor while preserving the normal bone structure and joint function. The ideal surgery is to completely remove the tumor while preserving the normal bone structure and joint function. The corresponding surgical procedures can be selected according to the different conditions of the tumor (Table 1 is the reference of surgical options for benign bone tumors at different stages). Commonly used surgical procedures include lesion scraping and bone grafting or bone cement filling (for stage I and most stage II cases); segmental resection and reconstruction (for recurrent stage II and most stage III cases); amputation is only used for patients with primary or secondary malignant GCT or recurrent recurrence with loss of limb preservation. For small portions of GCT that cannot be completely resected or for those patients who are not suitable for surgery, especially those with localized aggressiveness and/or recurrence after surgery, moderate doses of radiation therapy can be applied. However, many reports have shown that sarcoma may develop secondary to radiotherapy for giant cell tumors of bone, so radiotherapy can be tried unless surgery cannot completely remove the tumor or for those who are inoperable or have improved radiotherapy equipment, but must be followed closely for tumor malignancy. The newer methods are local radiotherapy with ultra-high voltage and particle radiotherapy.