IRF4 and neoplasm: We then ranked GC clusters from our data according to their annotations, following the normal GC differentiation lineage, and observed that XBP1 and IRF4 were activated while PRDM1 was unactivated in the late GC differentiation stage (MP2 cells) both at the RNA expression and motif activity levels (Fig. 4f), suggesting that the differentiation program of the MP2 B-cell lineage may be partially retained during tumor progression in PCNS DLBCL.