IL6 and primary central nervous system lymphoma: Thus, we cannot exclude the possibility that most of the suggested biomarkers of PCNSL (such as IL-6 [18], IL-10 [19] and CXCL-13 [17]) and soluble receptor proteins (such as sCD27 [15, 21] and sIL-2R [18]) were more abundant in PCNSL patients because they had originated in PCNSL tumor tissue.