When a bone nuclear scan is done, if there is an abnormal concentration of radionuclide in a certain bone area, there is a high possibility that it is a bone metastasis, but not all abnormal concentrations of radionuclide are bone metastases. Fractures caused by trauma or even old fractures, senile osteoporosis, especially severe osteoporosis, bone infections, including osteomyelitis, osteoarthritis, and benign tumors of bone, such as giant cell tumor of bone, can all cause abnormal concentrations of bone scan imaging agents. If the patient has a history of primary tumor with multiple abnormal concentrations, the first consideration is the bone metastasis of malignant tumor, but the benign diseases mentioned above can also cause active bone metabolism, and the differential diagnosis must be made as well.