OBJECTIVETo investigate the histogenetic origin of primary central nervous system diffuse large B-cell lymphoma (DLBCL) with respect to the stage of B-cell differentiation, and identification of the relevant prognostic markers.

METHODSImmunohistochemical staining (EnVision method) for CD10, bcl-6, MUM-1, CD138 and FOXP1 antigens was performed on 47 paraffin-embedded sections.

RESULTSCD10, bcl-6, MUM-1 and FOXP1 expression in the tumor cells were 6.4%, 53.2%, 91.5% and 93.6% respectively. There was no expression of CD138 in all the cases. Among the 47 patients, 43 cases (91.5%) showed an activated B-cell-like (ABC) phenotype: 21 (44.7%) were bcl-6+ and MUM-1+, suggesting an "activated germinal center (GC) B-cell-like" in origin; 22 (46.8%) were exclusively MUM-1+, suggesting an "activated non-GCB" in origin. No significant correlation of the classification and FOXP1 expression found on the outcome (P=0.279 and P=0.154).

CONCLUSIONSMost primary central nervous system DLBCL are shown belonging to the ABC subgroup, suggesting that primary central nervous system DLBCL is quite similar to a DLBCL subset, which is derived from late GC to early post-GC B cell. The classification and FOXP1 expression do not show prognostic value in primary central nervous system DLBCL.