Biological Characterization of Nodal versus Extranodal Presentation of Diffuse Large B-Cell Lymphoma using Immunohistochemistry

IntroductionDiffuse large B cell lymphoma (DLBCL) of primary nodal (PN) or primary extranodal (PEN) origin may differ immunophenotypically, in that PEN lymphoma cells may originate from activated rather than germinal center B (GCB) cells. We evaluated the relationship between DLBCL clinicopathological features, including expression of B-cell differentiation markers, and primary tumor site.Patients and MethodsExpression of CD10, Bcl-6, Bcl-2, and MUM1 was determined in paraffin-embedded tissues from 123 patients with DLBCL.ResultsOf the 123 patients with DLBCL, 40 (32.5%) had the GCB and 83 (67.5%) had the non-GCB phenotype. Fifty-one patients (42%) showed disease involvement at PEN sites, including 29 with disease in the gastrointestinal (GI) tract (14 in the stomach, 15 in the intestine). Of these 51 patients, 16 (31.4%) were classified with the GCB and 35 (68.5%) with the non-GCB subtype. There were no differences in the frequencies of GCB and non-GCB subtypes among primary sites. Of the 72 patients with PN DLBCL, 22 (31%) had the GCB and 50 (69%) had the non-GCB subtype. There were no differences in the frequencies of GCB and non-GCB subtypes between patients with PN and PEN DLBCL. Although lactate dehydrogenase (LDH) concentration > normal, stage >II, and rituximab-cyclophosphamide, doxorubicin, vincristine, and prednisone (RCHOP) treatment were independent predictors of overall survival (OS), GCB subtype, and presence of PEN disease failed to predict survival upon multivariate analysis.ConclusionThere was no difference in GCB and non-GCB phenotypes between patients with PN and PEN DLBCLs. Additional studies are needed to further assess molecular differences between the two groups.