In this perspective article, we focus on highlighting the importance of the determination of the chemokine (C-X-C) Ligand 13 index (ICXCL13) as an indicator of the presence of the meningeal tertiary lymphoid organ (mTLO) in patients with MS, since the presence of CXCL13 induces the formation of the germinal centers (GC) in the corresponding TLO of patients with this condition. This evidence concerns the gene CXCL13 and myeloid sarcoma.