The CSF of PCNSL patients has been reported to contain increased levels of cytokines such as interleukin (IL)6, IL-10, CXCL-12 and CXCL-13 [15–20], as well as the ectodomains of transmembrane proteins (sCD27 and sIL-2R) [15, 18, 21, 22]. Here, CXCL13 is linked to primary central nervous system lymphoma.