Bcl-6 and c-Myc are rarely co-expressed in adult diffuse large B-cell lymphoma

Cutaneous presentation of Double Hit Lymphoma: A Case Report With Review of the Literature

Diffuse large B-cell lymphoma (DLBCL) is the most common type of non-Hodgkin lymphoma (NHL), representing approximately 25% of diagnosed NHL. DLBCL is heterogeneous disease both clinically and genetically. The 3 most common chromosomal translocations in DLBCL involve the oncogenes BCL2, BCL6, and MYC. Double hit (DH) DLBCL is an aggressive form in which MYC rearrangement is associated with either BCL2 or BCL6 rearrangement. Patients typically present with a rapidly growing mass, often with B symptoms. Extranodal disease is often present. Though there is a paucity of prospective trials in this subtype, double hit lymphoma (DHL) has been linked to very poor outcomes when patients are treated with standard R-CHOP. There is, therefore, a lack of consensus regarding the standard treatment for DHL. Several retrospective analyses have been conducted to help guide treatment of this disease. These suggest that DA EPOCH-R may be the most promising regimen and that achievement of complete resolution predicts better long-term outcomes.

MYC expression and distribution in normal mature lymphoid cells

The distribution of the product of the proto-oncogene MYC in lymphoid tissue has not been established in three decades, due to a combination of factors including low abundance, short half-life, and antibody sensitivity and specificity. We sought to validate antibodies in order to define the expression and distribution of MYC in mature normal lymphoid cells by multiparametric immunophenotyping. Having validated two antibodies for flow cytometry and for immunohistochemistry, we analysed normal tonsil tissue. MYC is expressed predominantly in B cells, some of which are interfollicular large, activated, and cycling CD30+, IRF4+, AID± blasts. Follicular mantle, isotype-switched memory B cells and FcRH4/IRTA1+ B cells express MYC in a wide range of levels and are small non-proliferating CDKN1B/p27-positive or -negative resting B lymphocytes. Germinal centre founder cells, CD30+ BCL6± AID± germinal centre blasts, and a population of GC cells in the apical light zone express MYC. MYC is expressed in all phases of the cell cycle in activated and mature B cells, but rarely in other lymphoid types and only partially fulfils the predictions derived from extractive and ex vivo experiments of the past 30 years.

Prognostic sub-grouping of diffuse large B-cell lymphomas into germinal centre and post germinal centre groups by immunohistochemistry after 6 cycles of chemotherapy

INTRODUCTION

Diffuse large B-cell lymphomas (DLBCL) can be divided into germinal centre (GC-DLBCL) and post germinal centre (post GC-DLBCL) groups by applying immunohistochemical antibodies. As these subgroups respond differently to chemotherapy, it is possible at diagnosis to select a poor prognostic subgroup for aggressive treatment.

OBJECTIVE

To determine the frequencies of GC-DLBCL and post GC-DLBCL in patients by immunohistochemistry (IHC) and the clinical response after six cycles of chemotherapy.

SUBJECTS AND METHODS

In this descriptive study conducted in AFIP and CMH, Rawalpindi and NORI, Islamabad, from September 2010 to September 2011, a total of 75 pretreatment cases of DLBCL diagnosed during the study period were included. Cases were segregated in to GC-DLBCL and post GC-DLBCL groups according to results of immunohistochemistry markers CD10, BCL6 and MUM1. Immediate clinical response was assessed after 6 cycles of chemotherapy. Response was divided into complete response, partial response, stable disease or relapse or progression.

RESULTS

The mean age was 54.2 ± 15. Males were 53 (70.7%). Forty (53.3%) cases comprised the GC-DLBCL group; 25(62.5%) of them showed a complete response. Most patients of the post GC-DLBCL 19(54%) showed relapse/progression. Results of immediate clinical response in both prognostic subgroups were significant (p<0.05). Results regarding positivity with immunohistochemical antibodies CD10 (p 0.011), BCL6 (p 0.013) and MUM1 (p 0.000) regarding immediate clinical response were also significant.

CONCLUSION

GC-DLBCL group shows better response to CHOP chemotherapy regimen. Immunohistochemistry should be used to further classify DLBCL as this can enable us to select aggressive group for aggressive treatment. This manuscript is important because the study is the first to becarried out exclusively in Pakistan or our part of the world.

c-Myc overexpression promotes a germinal center-like program in Burkitt's lymphoma

The germinal center (GC) reaction has a pivotal function in human B-cell lymphomagenesis. Genetic aberrations occurring during somatic hypermutation and class switch recombination deregulate key factors controlling B-cell physiology and proliferation. Several human lymphoma entities are characterized by a constitutive GC phenotype and ongoing somatic hypermutation, but the molecular basis for this phenomenon is only partly understood. We have investigated the reasons for a constitutive GC-like program in Burkitt's lymphoma cells. Here, overexpression of c-Myc leads to a centroblast phenotype, promotes high constitutive expression of the key GC factors Bcl-6, E2A and activation-induced cytidine deaminase and contributes to proliferation and somatic hypermutation. Our findings elucidate how the activity of a pivotal transcription factor may freeze B-cell lymphoma cells in a constitutive GC-like state that is even maintained at an extrafollicular location.