CXCL12 and primary central nervous system lymphoma: The analysis of putative biomarkers in serum (IL-6, IL-8, IL-10, CXCL-12 and CXCL 13) and CSF (IL-10, CXCL-12 and CXCL 13) revealed aberrant protein levels in association with PCNSL [8,9,10,11,12].