Immunohistochemical subgroups in diffuse large B-cell lymphoma: Clinicopathologic study of 62 cases from Perú.

e18543 Background: Recent studies have shown that diffuse large B- cell lymphoma (DLBCL) cases with gene expression profiles of germinal centre B-like (GCB) had a better prognosis than DLBCL cases with gene expression profiles of activated B cells (non-GCB). DLBCL can be classified into three immunohistochemical (IHC) subgroups: GCB expressing CD10 and/or Bcl6 but not MUM1; activated GCB expressing at least one of GC B-cell markers and MUM1; and activated non-GCB expressing MUM1 but not GC B cell markers. Purpose: To determine the frequency of these patterns and the association with the clinical features, International Prognostic Index (IPI), clinical stage (CE), and treatment response. Methods: IHC analysis on paraffin-embedded tissues was performed using the streptavidin-avidin- biotin method in 62 cases of DLBCL. The IHC expression was performed as follows: positive (>30% of cells), and negative (≤30% of cells). Results: The male/female ratio was 1.2/1. The mean age was 58.6 (range: 22 - 89). 64.5%. Patients presented with nodal disease (n=40) and extranodal disease (n=22), CE I-II (n=35), CE III-IV (n=27), ECOG 0-1 (n=34), ECOG 2-4 (n=28), IPI BR-IB (n=37), and IPI IA-AR (n=25). 6 cases, 12 cases and 40 cases corresponded to GCB, activated GCB, and activated non-GCB patterns, respectively. There were 4 cases not evaluable. There was significant association between CE I-II and GCB subgroups as well as between CE III-IV and activated non-GCB subgroup (p< 0.05). Mean course of CHOP was 4.7. There was significant association between treatment response and CE (p<0.05), ECOG (p=0.009), and IPI (p=0,002) but not dependent of the patterns (p=0.746). The 3-year Overall survival (OS) for GCB subgroups and activated non-GCB subgroup was 67.9% and 60.3% respectively. The 3-year event-free survival (EFS) for these subgroups was 64.6% and 55.9%. Conclusions: The activated non-CGB was the most frequent IHC subgroup. Early CEs were associated with the GCB patterns. In our cases the IHC subgroups does not correlate with IPI and treatment response. No significant financial relationships to disclose.