CXCL13 and myeloid sarcoma: The B cell survival factor tumor necrosis factor (TNF) superfamily 13b (BAFF), the B cell-attracting chemokine (CXCL13), and the Chemokine (C-C motif) ligand 19 (CCL19) have been identified in the CSF and lesions of MS patients and are proposed to be key attractants [35,36,37].