Expression of the activation markers Blimp1, Foxp1 and pStat3 in extranodal diffuse large B-cell lymphomas

Different studies have suggested that the expression of biomarkers related to lymphoid cell activation may provide information on the behavior of DLBCL. Most studies have concentrated on nodal or a mixture of nodal and extranodal lymphomas. The differential expression and potential clinical impact of these markers in a homogeneous group of extranodal DLBCLs are not well defined. In this study, we investigated the expression of three activation markers, Blimp1, Foxp1 and pStat3, in a cohort of 35 extranodal DLBCLs homogeneously treated with R-CHOP. Immunohistochemical stains were evaluated using an immunoreactivity score on representative paraffin sections. Blimp1 was positive in 55% (19/35), Foxp1 in 60% (21/35), and pStat3 in 69% (24/35) of our cases. We did not observe any statistical differences in the expression of these markers in GCB and non-GCB tumors or in gastrointestinal and non-gastrointestinal tumors. Blimp1 expression was negatively correlated with overall survival (OS) (p=0.001) in the whole series and in the non-GCB group (Muris algorithm) (p=0.002). Foxp1 positivity and pStat3 positivity had no impact on the outcome of the patients in the global cohort, but they were associated with a better survival in the non-GCB subgroup (p=0.033, p=0.044 respectively). Multivariate analysis showed that Blimp1 expression but not COO was an independent negative prognostic factor for OS (HR=17.5, 95%, CI=2.2-141.1, p=0.007). Our results suggest that these markers are differentially expressed and have different impacts on outcome in extranodal DLBCLs compared to nodal tumors, emphasizing the need to evaluate separately these and probably other markers in these subsets of tumors.