Cell of Origin Classification of Diffuse Large B-Cell Lymphoma

Diffuse large B-cell lymphoma (DLBCL) is a neoplasm of medium-to-large B lymphoid cells with diffuse growth patterns. Although it is a potentially curable disease, around 40% of the cases are either refractory to primary treatment or relapse. Based on gene expression profiling (GEP), DLBCL can be classified as germinal center B-cell subtype (GCB) and activated B-cell subtype (ABC). About 10%-15% of cases do not convincingly fall into either of the two subtypes and hence remain unclassified. Most widely used and suggested by WHO is Hans algorithm comprising immunohistochemical markers CD10, B-cell lymphoma6 (BCL6), and IRF4/MUM1, which classifies CD10+ and CD10-/BCL6+/MUM1-DLBCL as GCB, while CD10-/BCL6+/MUM1 + and BCL6-DLBCL as non-GCB.

The aim of this study was to classify DLBCL into GCB and non-GCB subtypes using Hans Algorithm.

This was a retrospective study.

Twenty-eight histologically diagnosed cases of nodal (71.4%), as well as extranodal (28.6%) DLBCL, were taken over the period of 2 years with age ranging between 10 and 65 years with 19 males and 9 females. M: F = 2.1:1. Depending upon the site involved, a primary panel of immunohistochemistry (IHC) markers, namely CD20, CD3, LCA, EMA, and CK, followed by a secondary panel comprising CD10, CD19, CD30, LMP1, BCL2, BCL6, MUM1, MYC, and FOXP1 was used.

In this study, it was found that the non-GCB subtype was more common than the GCB subtype in Indian population.

Although the gold standard of GEP to assign cells of origin is using RNA microarray analysis, however, due to resource constraints and other limitations such as long turnaround times, IHC is the next acceptable alternative.