CXCR4 and synovial sarcoma: Because earlier research showed that high levels of CXCR4 expression are linked to a poor prognosis and a high incidence of metastasis in bone and STS (Kim et al., 2011; Li et al., 2017), the results of the research team mentioned in the preceding paragraph (Pazzaglia et al., 2019) suggested that CXCR4 plays an important role in cancer cell movement between the main and metastatic sites in SS.