PRDM1 expression levels in marginal zone lymphoma and lymphoplasmacytic lymphoma.

PRDM1 (BLIMP1) is a transcription repressor protein shown to be involved in B-cell differentiation into plasma cells. Marginal zone lymphomas (MZL) and lymphoplasmacytic lymphomas (LPL) are B cell lymphomas that both show some degree of plasmacytic differentiation and thus can sometimes constitute a difficult differential diagnosis. In this study, we investigated if MZL and LPL have abnormalities in the expression of PRDM1 beta and if there are any differences in expression between these two entities. After interrogating 42 samples (15 marginal zone lymphomas, 9 lymphoplasmacytic lymphomas, 3 follicular lymphomas, and 13 normal/control samples), we have found that a significant percentage of MZL and LPL cases harbor abnormalities (67% and 44%, respectively) involving the PRDM1-β transcript (P=0.004). By immunohistochemistry, PRDM1 positive staining (>5%) was more common in MZL. We conclude that PRDM1-β may play a role in the pathogenesis of these low-grade lymphomas with plasmacytic differentiation.