Diffuse aggressive B-cell lymphomas

Diffuse Large B-Cell Lymphoma in Kenya: MYC, BCL2, and the Cell of Origin

PURPOSE

Diffuse large B-cell lymphoma (DLBCL) is the most commonly diagnosed non-Hodgkin lymphoma in adults in Kenya. Cell of origin (COO) and double expression of MYC and BCL2 are two important prognostic factors for DLBCL. A small subset (5% to 10%) of DLBCL cases show positivity for CD5 and are associated with poor prognosis, whereas CD30 antigen, seen in up to 10% of cases, may be a useful target for therapy. We sought to determine the prevalence of MYC/BCL2 double expression, COO, and proportion of Epstein-Barr virus positivity among patients with DLBCL diagnosed at a tertiary referral laboratory in Kenya.

PATIENTS AND METHODS

All cases of DLBCL diagnosed from 2012 through 2015 in our pathology department were analyzed. Tumor tissue microarray sections were stained with CD20, CD3, CD5, CD30, BCL2, BCL6, CD10, MUM1, MYC, and Ki67, classified for COO on the basis of the Hans algorithm, and subjected to Epstein-Barr virus-encoded small RNAs in situ hybridization.

RESULTS

Among 165 DLBCL cases, the median age was 50 years, and there was no sex predilection. Only 18 (10.9%) cases showed double expression for MYC and BCL2. Germinal center B (GCB)-cell type DLBCL accounted for 67 cases (40.6%) and 97 cases (59.4%) were classified as non-GCB. The mean Ki67 proliferation index was significantly higher in the double-expressing (45%) and non-GCB groups (36%) compared with the non–double-expressing group (29%) and GCB group (26%). Sixteen cases (9.7%) were Epstein-Barr virus-encoded small RNAs positive, 12 (75%) of which were non-GCB.

CONCLUSION

DLBCL in Kenya is seen in much younger patients with the poor prognostic non–GCB-type accounting for 59.4% of cases. MYC and BCL2 double expression was seen in fewer tumors than reported in the literature and in significantly older patients.

Cytologic perspectives on neoteric B-cell lymphoproliferative disorders

The 2008 World Health Organization (WHO) classification of hematopoietic and lymphoid tissues has been recently revised, and publication of the updated 2016 version is expected soon. Given that cytopathologists are often involved in the diagnosis of primary, recurrent, and transformed lymphoproliferative disorders, knowledge of updates to the WHO lymphoma classification, including terminology, pathogenesis, ancillary techniques, and targeted therapies is necessary. Herein, we reference the last decade of cytology specific literature for seven newer B-cell disorders and provide illustrative examples of each entity from our files.

Epstein-Barr virus-specific CD8(+) T lymphocytes from diffuse large B cell lymphoma patients are functionally impaired

Epstein-Barr virus (EBV) is a persistent virus with oncogenic capacity that has been implicated in the development of aggressive B cell lymphomas, primarily in immunosuppressed individuals, although it can be present in immunocompetent individuals. Changes in the function and clonal diversity of T lymphocytes might be implied by viral persistence and lymphoma development. The aim of the present study was to evaluate the frequency, phenotype, function and clonotypical distribution of EBV-specific T cells after peripheral blood stimulation with a virus lysate in newly diagnosed patients with diffuse large B cell lymphoma (DLBCL) aged more than 50 years without prior histories of clinical immunosuppression compared with healthy controls. Our results showed impaired EBV-specific immune responses among DLBCL patients that were associated primarily with decreased numbers of central and effector memory CD8(+) T lymphocytes. In contrast to healthy controls, only a minority of the patients showed CD4(+)/tumour necrosis factor (TNF)-α(+) T cells expressing T cell receptor (TCR)-Vβ17 and CD8(+)/TNF-α(+) T cells with TCR-Vβ5·2, Vβ9 and Vβ18 in response to EBV. Notably, the production of TNF-α was undetectable among TCR-Vβ5·3(+), Vβ11(+), Vβ12(+), Vβ16(+) and Vβ23(+) CD8(+) T cells. In addition, we observed decreased numbers of CD4(+)/TNF-α(+) and CD8(+)/TNF-α(+), CD8(+)/interleukin (IL)-2(+) and CD8(+)/TNF-α(+)/IL-2(+) T lymphocytes in the absence of T cells capable of producing TNF-α, IL-2 and IFN-γ after EBV stimulation simultaneously. Moreover, DLBCL patients displayed higher IL-10 levels both under baseline conditions and after EBV stimulation. These findings were also observed in patients with positive EBV viral loads. Prospective studies including a large number of patients are needed to confirm these findings.

Age-associated Epstein-Barr virus-specific T cell responses in seropositive healthy adults

Epstein-Barr virus (EBV) is present in 95% of the world's adult population. The immune response participates in immune vigilance and persistent infection control, and this condition is maintained by both a good quality (functionality) and quantity of specific T cells throughout life. In the present study, we evaluated EBV-specific CD4(+) and CD8(+) T lymphocyte responses in seropositive healthy individuals younger and older than 50 years of age. The assessment comprised the frequency, phenotype, functionality and clonotypic distribution of T lymphocytes. We found that in both age groups a similar EBV-specific T cell response was found, with overlapping numbers of tumour necrosis factor (TNF)-α(+) T lymphocytes (CD4(+) and CD8(+)) within the memory and effector cell compartments, in addition to monofunctional and multi-functional T cells producing interleukin (IL)-2 and/or interferon (IFN)-γ. However, individuals aged more than 50 years showed significantly higher frequencies of IL-2-producing CD4(+) T lymphocytes in association with greater production of soluble IFN-γ, TNF-α and IL-6 than subjects younger than 50 years. A polyclonal T cell receptor (TCR)-variable beta region (Vβ) repertoire exists in both age groups under basal conditions and in response to EBV; the major TCR families found in TNF-α(+) /CD4(+) T lymphocytes were Vβ1, Vβ2, Vβ17 and Vβ22 in both age groups, and the major TCR family in TNF-α(+) /CD8(+) T cells was Vβ13·1 for individuals younger than 50 years and Vβ9 for individuals aged more than 50 years. Our findings suggest that the EBV-specific T cell response (using a polyclonal stimulation model) is distributed throughout several T cell differentiation compartments in an age-independent manner and includes both monofunctional and multi-functional T lymphocytes.

Aggressive B-cell lymphomas: how many categories do we need?

Aggressive B-cell lymphomas are diverse group of neoplasms that arise at different stages of B-cell development and by various mechanisms of neoplastic transformation. The aggressive B-cell lymphomas include many types, subtypes and variants of diffuse large B-cell lymphoma (DLBCL), Burkitt lymphoma (BL), mantle cell lymphoma and its blastoid variant, and B lymphoblastic lymphoma. Differences in histology, cytogenetic and molecular abnormalities, as well as the relationship with the tumor microenvironment, help define characteristic signatures for these neoplasms, and in turn dictate potential therapeutic targets. Rather than survey the entire spectrum of aggressive B-cell lymphomas, this report aims to identify and characterize important clinically aggressive subtypes of DLBCL, and explore the relationship of DLBCL to BL and the gray zone between them (B-cell lymphoma unclassifiable with features intermediate between DLBCL and BL).

Genomic profiling using array comparative genomic hybridization define distinct subtypes of diffuse large B-cell lymphoma: a review of the literature

Diffuse large B-cell lymphoma (DLBCL) is the most common type of non-Hodgkin Lymphoma comprising of greater than 30% of adult non-Hodgkin Lymphomas. DLBCL represents a diverse set of lymphomas, defined as diffuse proliferation of large B lymphoid cells. Numerous cytogenetic studies including karyotypes and fluorescent in situ hybridization (FISH), as well as morphological, biological, clinical, microarray and sequencing technologies have attempted to categorize DLBCL into morphological variants, molecular and immunophenotypic subgroups, as well as distinct disease entities. Despite such efforts, most lymphoma remains undistinguishable and falls into DLBCL, not otherwise specified (DLBCL-NOS). The advent of microarray-based studies (chromosome, RNA, gene expression, etc) has provided a plethora of high-resolution data that could potentially facilitate the finer classification of DLBCL. This review covers the microarray data currently published for DLBCL. We will focus on these types of data; 1) array based CGH; 2) classical CGH; and 3) gene expression profiling studies. The aims of this review were three-fold: (1) to catalog chromosome loci that are present in at least 20% or more of distinct DLBCL subtypes; a detailed list of gains and losses for different subtypes was generated in a table form to illustrate specific chromosome loci affected in selected subtypes; (2) to determine common and distinct copy number alterations among the different subtypes and based on this information, characteristic and similar chromosome loci for the different subtypes were depicted in two separate chromosome ideograms; and, (3) to list re-classified subtypes and those that remained indistinguishable after review of the microarray data. To the best of our knowledge, this is the first effort to compile and review available literatures on microarray analysis data and their practical utility in classifying DLBCL subtypes.

Although conventional cytogenetic methods such as Karyotypes and FISH have played a major role in classification schemes of lymphomas, better classification models are clearly needed to further understanding the biology, disease outcome and therapeutic management of DLBCL. In summary, microarray data reviewed here can provide better subtype specific classifications models for DLBCL.

Dominant genetic aberrations and coexistent EBV infection in HIV-related oral plasmablastic lymphomas

We present common cytogenetic features in the largest cohort of plasmablastic lymphoma (PBL) of the oral cavity published to date. This cohort included 45 patients, 32 of whom had a known HIV status, of which 31 were HIV positive. Ninety eight per cent of all PBL cases were known to be EBV positive. In line with previous studies, we found that rearrangements of the MYC gene was the most common genetic abnormality seen in 60% of cases with the immunoglobulin heavy chain (IGH) locus as a partner in 51% of cases. Additional complex genetic aberrations were frequent, in particular, an increased copy number of the CCND1 gene was seen in 41% of cases with true amplification of CCND1 in 15% of cases. Aneuploidy was also observed for the BCL6 gene in 28% of cases. Interestingly, rearrangements of both IGH genes were detected in 16% of cases with t(14;18) and t(11;14) respectively involved in conjunction with a t(8;14) in two cases. These bi-allelic IGH rearrangements have not been described before in oral PBL. Our results reinforce the notion that EBV infection and MYC rearrangements are important events in the pathogenesis of oral PBL. The genetic diversity and complexity observed in these cases, underlines the importance to genetically characterise PBL patients at presentation as this may inform the choice of more effective treatment modalities.