Objective: To perform immunophenotyping and molecular genetic analysis for diffuse large B-cell lymphoma (DLBCL), and to explore their correlation and implication for prognosis.
Methods: Immunohistochemical streptavidin peroxidase (SP) method was used to determine the expression of CD10, BCL6 and MUM1 in 59 cases of DLBCL. A Hans algorithm was used to classify DLBCL into germinal center B-cell (GCB) and non-GCB subtypes. Interphase fluorescence in situ hybridization (FISH) assay was performed on paraffin-embedded lymphoma tissue sections to detect translocations and amplifications of BCL6, BCL2 and MYC genes with dual-color break-apart BCL6 probe, dual-color dual-fusion IgH/ BCL2 probe and dual-color break-apart MYC probe, respectively.
Results: In the 59 cases of DLBCL, 28.8% (17/59) belonged to GCB subtype, and 71.2% (42/59) belonged to non-GCB subtype. The incidences of BCL6, BCL2 and MYC gene translocations were 24.1% (14/58), 1.7% (1/59) and 5.3% (3/57), respectively. The incidences of BCL6, BCL2 and MYC gene amplifications were 17.2% (10/58), 22.0% (13/59) and 21.1% (12/57), respectively. BCL6 amplification was not correlated with BCL6 translocation (P=0.424), but was correlated with amplifications of BCL2 and MYC (C=0.405 and 0.403, respectively, P <0.01). The incidence of BCL6 translocation in GCB type was higher than that in non-GCB type, and amplifications of BCL6, BCL2 or MYC were more frequently encountered in non-GCB type, though no statistical significance was detected (P=0.089 and 0.106, respectively). By univariate analysis, immunophenotyping and international prognostic index (IPI) exerted a significant effect on overall survival (OS) (P=0.047 and 0.001, respectively), but to which BCL6 translocation and amplification of the 3 genes were not related (P=0.150 and 0.444, respectively). By multivariate analysis, IPI score was the only independent prognostic factor for OS (RR =3.843, P=0.017).
Conclusion: The GCB subtype of DLBCL is less common in the patient cohort. Common genetic aberrations have included BCL6 translocation and BCL6, BCL2 and MYC amplifications. Amplification of the 3 genes is strongly correlated with each other, and the incidence of BCL2 translocation is low. Immunophenotyping only has minor significance for the prognosis. Genetic aberrations cannot predict the clinical outcome of DLBCL.