Incidence of diffuse large B-cell lymphoma of germinal center B-cell origin in whole diffuse large B-cell lymphoma: tissue fluorescence in situ hybridization using t(14;18) compared with immunohistochemistry.

Diffuse large B-cell lymphoma (DLBCL) can be divided into prognostically important categories such as germinal center B (GCB)-like and non-GCB-like groups. The t(14;18)(q32;q21) translocation defines a unique subset of DLBCL cases with a GCB gene expression profile. Two-color fluorescence in situ hybridization (FISH) analysis was applied to detect t(14;18) (q32;q21) in the nuclei of paraffin-embedded tissue sections from 61 patients with de novo DLBCL. Nine (15%) of 61 cases had a positive pattern. Fifty-seven cases were subclassified in an immunohistochemical study with anti-CD10, anti-bcl-6, and anti-MUM1 antibodies. In this classification, 21 cases (37%) were placed in the GCB group, and 36 (63%) were placed in the non-GCB group. There was a discrepancy between t(14;18) occurrence and bcl-2 protein expression. Bcl-2 protein expression was positive in 40 (67%) of 60 cases. The expression of bcl-2 protein in the GCB and non-GCB groups was not significantly different: 15 (71%) of 21 cases in the GCB group and 24 (67%) of 36 cases in the non-GCB group tested positive. We found no difference between the FISH-positive and FISH-negative groups in overall survival time (P = .6019, log-rank test). The overall survival rates of GCB and non-GCB groups did not differ significantly by immunohistochemical classification (P = .5399, log-rank test). Overall survival was significantly longer in the group with a low International Prognostic Index (IPI) score than in the group with a high IPI score (P = .0002, log-rank test). Our results suggest that immunohistochemical study and cytogenetic study with t(14;18) FISH cannot predict the clinical outcomes of DLBCL patients. A study with a larger number of patients may show a difference in clinical outcomes between FISH-positive and FISH-negative groups and between GCB and non-GCB groups.