CD4 and Ewing sarcoma: Due to the immunogenic role of CCL21 and its immunotherapeutic potential, we studied the CCL21 expression in primary therapy-naïve Ewing sarcoma samples and EWS cell lines by analyzing the RNA expression levels of CCL21. The measured RNA expression levels were correlated with the number of infiltrating T cells and the CD4+/CD8+ T cell ratio in Ewing sarcoma samples.