We plan to collect peripheral blood serum samples of osteosarcoma patients at different stages, isolate and detect the XIST level in serum exosomes, so as to clarify the difference between osteosarcoma patients and normal people, as well as the difference between the XIST level in serum exosomes of osteosarcoma patients at different stages. The gene discussed is XIST; the disease is osteosarcoma.