CXCR6 and Ewing sarcoma/peripheral primitive neuroectodermal tumor: Studies on patients show that CXCR6 expression is greater in metastasis than in primary tumors of such cancers as cervical cancer [125], Ewing sarcoma family tumor [126], gastric cancer [102,118], melanomas [127], nasopharyngeal carcinoma [112], ovarian carcinoma [128], papillary thyroid cancer [114], and prostate cancer [116].