Double-hit B-cell Lymphomas With BCL6 and MYC Translocations Are Aggressive, Frequently Extranodal Lymphomas Distinct From BCL2 Double-hit B-cell Lymphomas

Prognostic impact of concurrent MYC and BCL6 rearrangements and expression in de novo diffuse large B-cell lymphoma

Double-hit B-cell lymphoma is a common designation for a group of tumors characterized by concurrent translocations of MYC and BCL2, BCL6, or other genes. The prognosis of concurrent MYC and BCL6 translocations is not well known. In this study, we assessed rearrangements and expression of MYC, BCL2 and BCL6 in 898 patients with de novo diffuse large B-cell lymphoma treated with standard chemotherapy (cyclophosphamide, doxorubicin, vincristine, and prednisone plus rituximab). Neither BCL6 translocation alone (more frequent in activated B-cell like diffuse large B-cell lymphoma) nor in combination with MYC translocation (observed in 2.0% of diffuse large B-cell lymphoma) predicted poorer survival in diffuse large B-cell lymphoma patients. Diffuse large B-cell lymphoma patients with MYC/BCL6 co-expression did have significantly poorer survival, however, MYC/BCL6 co-expression had no effect on prognosis in the absence of MYC/BCL2 co-expression, and had no additive impact in MYC+/BCL2+ cases. The isolated MYC+/BCL6+/BCL2- subset, more frequent in germinal center B-cell like diffuse large B-cell lymphoma, had significantly better survival compared with the isolated MYC+/BCL2+/BCL6- subset (more frequent in activated B-cell like diffuse large B-cell lymphoma). In summary, diffuse large B-cell lymphoma patients with either MYC/BCL6 rearrangements or MYC/BCL6 co-expression did not always have poorer prognosis; MYC expression levels should be evaluated simultaneously; and double-hit B-cell lymphoma needs to be refined based on the specific genetic abnormalities present in these tumors.

Novel drug targets for personalized precision medicine in relapsed/refractory diffuse large B-cell lymphoma: a comprehensive review

Diffuse large B-cell lymphoma (DLBCL) is a clinically heterogeneous lymphoid malignancy and the most common subtype of non-Hodgkin's lymphoma in adults, with one of the highest mortality rates in most developed areas of the world. More than half of DLBLC patients can be cured with standard R-CHOP regimens, however approximately 30 to 40 % of patients will develop relapsed/refractory disease that remains a major cause of morbidity and mortality due to the limited therapeutic options.Recent advances in gene expression profiling have led to the identification of at least three distinct molecular subtypes of DLBCL: a germinal center B cell-like subtype, an activated B cell-like subtype, and a primary mediastinal B-cell lymphoma subtype. Moreover, recent findings have not only increased our understanding of the molecular basis of chemotherapy resistance but have also helped identify molecular subsets of DLBCL and rational targets for drug interventions that may allow for subtype/subset-specific molecularly targeted precision medicine and personalized combinations to both prevent and treat relapsed/refractory DLBCL. Novel agents such as lenalidomide, ibrutinib, bortezomib, CC-122, epratuzumab or pidilizumab used as single-agent or in combination with (rituximab-based) chemotherapy have already demonstrated promising activity in patients with relapsed/refractory DLBCL. Several novel potential drug targets have been recently identified such as the BET bromodomain protein (BRD)-4, phosphoribosyl-pyrophosphate synthetase (PRPS)-2, macrodomain-containing mono-ADP-ribosyltransferase (ARTD)-9 (also known as PARP9), deltex-3-like E3 ubiquitin ligase (DTX3L) (also known as BBAP), NF-kappaB inducing kinase (NIK) and transforming growth factor beta receptor (TGFβR).This review highlights the new insights into the molecular basis of relapsed/refractory DLBCL and summarizes the most promising drug targets and experimental treatments for relapsed/refractory DLBCL, including the use of novel agents such as lenalidomide, ibrutinib, bortezomib, pidilizumab, epratuzumab, brentuximab-vedotin or CAR T cells, dual inhibitors, as well as mechanism-based combinatorial experimental therapies. We also provide a comprehensive and updated list of current drugs, drug targets and preclinical and clinical experimental studies in DLBCL. A special focus is given on STAT1, ARTD9, DTX3L and ARTD8 (also known as PARP14) as novel potential drug targets in distinct molecular subsets of DLBCL.

Update in large cell lymphoma: understanding the pathology report

The diffuse aggressive large B-cell lymphomas are a heterogeneous group of B-cell malignancies. Although many are readily recognized due to characteristic clinical and pathologic features, several problematic areas still exist in diagnosis of these lymphomas due to a variety of reasons that include imprecise or difficult-to-apply diagnostic criteria, gaps in our understanding of lymphoma biology, and limitations in technologies available in the clinical laboratory compared to the research laboratory. This may result in some degree of confusion in the pathology report, particularly if the issues are not clearly explained, leading to frustration or misinterpretation on the part of the reader. In this review, I will discuss the pathologic features of a subset of the WHO 2008 classification diffuse aggressive large B-cell lymphomas, focusing on areas in which difficulties exist in diagnosis and/or biomarker marker assessment. A deeper understanding of the issues and areas of uncertainty due to limitations in our knowledge about the biology of these diseases should lead to better communication between pathologists and clinicians.

Impact of Single or Combined Genomic Alterations of TP53, MYC, and BCL2 on Survival of Patients With Diffuse Large B-Cell Lymphomas: A Retrospective Cohort Study

MYC and BCL2 translocations as well as TP53 deletion/mutation are known risk factors in diffuse large B-cell lymphoma (DLBCL) but their interplay is not well understood.In this retrospective cohort study, we evaluated the combined prognostic impact of TP53 deletion and mutation status, MYC and BCL2 genomic breaks in tumor samples of 101 DLBCL patients. The cohort included 53 cases with MYC rearrangements (MYC+).TP53 deletions/mutations (TP53+) were found in 32 of 101 lymphomas and were equally distributed between MYC+ and MYC- cases (35.8% vs. 27.1%). TP53+ lymphomas had lower responses to treatment than TP53- (complete remission 34.4% vs. 60.9%; P = 0.01). TP53 alteration was the dominant independent prognostic factor in multivariate analysis (P = 0.01). Overall survival (OS) varied considerably between subgroups with different genomic alterations: Patients with sole MYC translocation, and interestingly, with triple MYC+/BCL2+/TP53+ aberration had favorable outcomes (median OS not reached) similar to patients without genomic alterations (median OS 65 months). In contrast, patients with MYC+/BCL2+/TP53- double-hit lymphomas (DHL) (28 months), MYC+/BCL2-/TP53+ lymphomas (10 months) or sole TP53 mutation/deletion (12 months) had a poor median OS. Our findings demonstrate differences in OS of DLBCL patients depending on absence or presence of single or combined genetic alterations of MYC, BCL2, and TP53. Cooccurrence of TP53 and BCL2 aberrations ameliorated the poor prognostic impact of single TP53+ or BCL2+ in MYC positive patients.This pilot study generates evidence for the complex interplay between the alterations of genetic pathways in DLBCL, which goes beyond the concept of DHL. The variable survival of DLBCL patients dependent on single or combined alterations in the TP53, MYC, and BCL2 genes indicates the need for comprehensive genomic diagnosis.

MYC-driven aggressive B-cell lymphomas: biology, entity, differential diagnosis and clinical management

MYC, a potent oncogene located at chromosome locus 8q24.21, was identified initially by its involvement in Burkitt lymphoma with t(8;14)(q24;q32). MYC encodes a helix-loop-helix transcription factor that accentuates many cellular functions including proliferation, growth and apoptosis. MYC alterations also have been identified in other mature B-cell neoplasms and are associated with aggressive clinical behavior. There are several regulatory factors and dysregulated signaling that lead to MYC up-regulation in B-cell lymphomas. One typical example is the failure of physiological repressors such as Bcl6 or BLIMP1 to suppress MYC over-expression. In addition, MYC alterations are often developed concurrently with other genetic alterations that counteract the proapoptotic function of MYC. In this review, we discuss the physiologic function of MYC and the role that MYC likely plays in the pathogenesis of B-cell lymphomas. We also summarize the role MYC plays in the diagnosis, prognostication and various strategies to detect MYC rearrangement and expression.

Impact of oncogene rearrangement patterns on outcomes in patients with double-hit non-Hodgkin lymphoma

BACKGROUND

Double-hit lymphomas (DHLs) are collectively defined as B-cell non-Hodgkin lymphomas harboring rearrangements of MYC as well as B-cell lymphoma 2 (BCL2) and/or B-cell lymphoma 6 (BCL6). To the authors' knowledge, the impact of specific oncogene rearrangements on outcomes of patients with DHL who are treated with immunochemotherapy has not been previously described.

METHODS

The authors identified patients whose diagnostic tissue specimens underwent metaphase karyotyping or fluorescence in situ hybridization for MYC as well as both BCL2 and BCL6 rearrangements. Cohorts were defined by the presence (+) or absence (-) of rearrangements: MYC+/BCL2+/BCL6- (BCL2-DHL), MYC+/BCL2-/BCL6+ (BCL6-DHL), and MYC+/BCL2+/BCL6+ (triple-hit lymphoma; THL).

RESULTS

A total of 117 patients were included in the current analysis (76 BCL2-DHL patients, 16 BCL6-DHL patients, and 25 THL patients). Compared with patients with BCL2-DHL, those with BCL6-DHL were more likely to be classified as having a non-germinal center cell of origin, presented with extranodal disease, and appeared to achieve higher rates of complete response despite receiving intensive induction therapy less frequently. However, patients with BCL6-DHL experienced a shorter median overall survival if achieving an initial complete response compared with patients with BCL2-DHL. Patients with THL experienced survival outcomes similar to those of patients with BCL2-DHL.

CONCLUSIONS

Recognition of the specific oncogene rearrangements may be of prognostic value and potentially guide future therapeutic strategies for patients with DHL.

Outcome prediction by extranodal involvement, IPI, R-IPI, and NCCN-IPI in the PET/CT and rituximab era: A Danish-Canadian study of 443 patients with diffuse-large B-cell lymphoma

18F-fluorodeoxyglucose PET/CT (PET/CT) is the current state-of-the-art in the staging of diffuse large B-cell lymphoma (DLBCL) and has a high sensitivity for extranodal involvement. Therefore, reassessment of extranodal involvement and the current prognostic indices in the PET/CT era is warranted. We screened patients with newly diagnosed DLBCL seen at the academic centers of Aalborg, Copenhagen, and British Columbia for eligibility. Patients that had been staged with PET/CT and treated with R-CHOP(-like) 1(st) line treatment were retrospectively included. In total 443 patients met the inclusion criteria. With a median follow-up of 2.4 years, the 3-year overall (OS) and progression-free survival (PFS) were 73% and 69%, respectively. The Ann Arbor classification had no prognostic impact in itself with the exception of stage IV disease (HR 2.14 for PFS, P<0.01). Extranodal involvement was associated with a worse outcome in general, and in particular for patients with involvement of >2 extranodal sites, including HR 7.81 (P < 0.001) for PFS for >3 sites. Bone/bone marrow involvement was the most commonly involved extranodal site identified by PET/CT (29%) and was associated with an inferior PFS and OS. The IPI, R-IPI, and NCCN-IPI were predictive of PFS and OS, and the two latter could identify a very good prognostic subgroup with 3-year PFS and OS of 100%. PET/CT-ascertained extranodal involvement in DLBCL is common and involvement of >2 extranodal sites is associated with a dismal outcome. The IPI, R-IPI, and NCCN-IPI predict outcome with high accuracy.

Triple-hit B-cell Lymphoma With MYC, BCL2, and BCL6 Translocations/Rearrangements: Clinicopathologic Features of 11 Cases

Lymphomas with translocations/rearrangements of MYC, BCL2, and BCL6, so-called triple-hit B-cell lymphoma, are rare, and few studies on these tumors are available in the literature. We report 11 cases of triple-hit B-cell lymphoma and characterize their clinicopathologic findings. All patients were men, with a median age of 64 years (range, 45 to 80 y), and 4 patients had antecedent or concurrent follicular lymphoma. Using the 2008 World Health Organization classification, these cases were classified as: 5 B-cell lymphoma, unclassifiable, with features intermediate between diffuse large B-cell lymphoma (DLBCL) and Burkitt lymphoma; 4 DLBCL; 1 DLBCL with concurrent follicular lymphoma; and 1 low-grade follicular lymphoma. All cases were positive for CD10, BCL2, and FOXP1. Ten of 11 cases were positive for CD20. MYC expression was high in 10/11 (91%), BCL6 was positive in 8/11 (73%), and MUM1/IRF4 was positive in 6/11 (55%) cases. T-cell antigens, TdT, and Epstein-Barr virus-encoded RNA were negative in all cases. Ten of 11 cases showed a high proliferation index-70% to 100%, and the follicular lymphoma had a 30% proliferation rate. Using most algorithms, all cases belonged to germinal center B-cell-like group. All patients received standard or more aggressive immunochemotherapy regimens. Three patients had no response to chemotherapy; 4 patients showed a partial response; 2 patients had complete remission after chemotherapy; and 2 patients had just begun chemotherapy. Three patients underwent a stem cell transplant. The median follow-up time was 5.3 months. Five patients died, and 6 patients were alive at last follow-up. Two patients who underwent stem cell transplant after complete response to chemotherapy were in remission with 16 to 19 months of clinical follow-up. In summary, triple-hit lymphomas are clinically aggressive tumors associated with a poor prognosis. Patients often respond poorly to chemotherapy, but a subset may completely respond to chemotherapy followed by stem cell transplant.

Detection of Enhancer-Associated Rearrangements Reveals Mechanisms of Oncogene Dysregulation in B-cell Lymphoma

B-cell lymphomas frequently contain genomic rearrangements that lead to oncogene activation by heterologous distal regulatory elements. We used a novel approach called "pinpointing enhancer-associated rearrangements by chromatin immunoprecipitation," or PEAR-ChIP, to simultaneously map enhancer activity and proximal rearrangements in lymphoma cell lines and patient biopsies. This method detects rearrangements involving known cancer genes, including CCND1, BCL2, MYC, PDCD1LG2, NOTCH1, CIITA, and SGK1, as well as novel enhancer duplication events of likely oncogenic significance. We identify lymphoma subtype-specific enhancers in the MYC locus that are silenced in lymphomas with MYC-activating rearrangements and are associated with germline polymorphisms that alter lymphoma risk. We show that BCL6-locus enhancers are acetylated by the BCL6-activating transcription factor MEF2B, and can undergo genomic duplication, or target the MYC promoter for activation in the context of a "pseudo-double-hit" t(3;8)(q27;q24) rearrangement linking the BCL6 and MYC loci. Our work provides novel insights regarding enhancer-driven oncogene activation in lymphoma.

SIGNIFICANCE

We demonstrate a novel approach for simultaneous detection of genomic rearrangements and enhancer activity in tumor biopsies. We identify novel mechanisms of enhancer-driven regulation of the oncogenes MYC and BCL6, and show that the BCL6 locus can serve as an enhancer donor in an "enhancer hijacking" translocation.

MYC or BCL2 copy number aberration is a strong predictor of outcome in patients with diffuse large B-cell lymphoma

Diffuse large B-cell lymphoma (DLBCL) is the most common non-Hodgkin lymphoma (NHL). Patients with DLBCL harboring MYC aberrations concurrent with BCL2 or/and BCL6 aberrations constitute a specific group with extremely poor outcome. In this study, we retrospectively investigated the incidence and prognosis of MYC, BCL2, and BCL6 aberrations with DLBCL patients in Chinese population. We applied fluorescence in situ hybridization and immunohistochemical analysis in 246 DLBCL patients. The results showed that patients with MYC or BCL2 copy number aberration (CNA) had significantly worse overall survival (OS) and progression-free survival (PFS) than negative cases (P < 0.0001). Patients with both MYC and BCL2 CNA had similar outcomes to those with classic double hit lymphoma or protein double expression lymphoma (MYC and BCL2/BCL6 coexpression). By multivariate analysis, MYC CNA, BCL2 CNA and double CNA were the independent worse prognostic factors. In conclusions, patients with MYC or BCL2 CNA constituted a unique group with extremely poor outcome and may require more aggressive treatment regimens.

Isolated MYC cytogenetic abnormalities in diffuse large B-cell lymphoma do not predict an adverse clinical outcome

In this study, we investigated the significance of MYC, BCL2 and BCL6 gene abnormalities in a cohort of 205 diffuse large B-cell lymphoma (DLBCL) patients studied by conventional and/or fluorescence in situ hybridization cytogenetic analysis. Combining these methods, 172 cases (84%) were classified as MYC-, 17 (8%) were MYC+/BCL2-/BCL6-, and 16 (8%) were double/triple-hit lymphomas (i.e. MYC+/BCL2+, MYC+/BCL6+, or MYC+/BCL2+/BCL6+). We found a significant difference in event-free survival (EFS) among the three groups (p = 0.02), with the double/triple-hit group having the worst EFS. Patients who were MYC+, but BCL2- and BCL6-, had the best EFS. We conclude that patients with MYC+ DLBCL, but without BCL2 or BCL6 abnormalities, do not have a worse outcome when compared to those who are MYC-. However, patients with double/triple-hit DLBCL have a very poor outcome and should be treated with aggressive or novel therapies.

The prognosis of MYC translocation positive diffuse large B-cell lymphoma depends on the second hit

A proportion of MYC translocation positive diffuse large B‐cell lymphomas (DLBCL) harbour a BCL2 and/or BCL6 translocation, known as double‐hit DLBCL, and are clinically aggressive. It is unknown whether there are other genetic abnormalities that cooperate with MYC translocation and form double‐hit DLBCL, and whether there is a difference in clinical outcome between the double‐hit DLBCL and those with an isolated MYC translocation. We investigated TP53 gene mutations along with BCL2 and BCL6 translocations in a total of 234 cases of DLBCL, including 81 with MYC translocation. TP53 mutations were investigated by PCR and sequencing, while BCL2 and BCL6 translocation was studied by interphase fluorescence in situ hybridization. The majority of MYC translocation positive DLBCLs (60/81 = 74%) had at least one additional genetic hit. In MYC translocation positive DLBCL treated by R‐CHOP (n = 67), TP53 mutation and BCL2, but not BCL6 translocation had an adverse effect on patient overall survival. In comparison with DLBCL with an isolated MYC translocation, cases with MYC/TP53 double‐hits had the worst overall survival, followed by those with MYC/BCL2 double‐hits. In MYC translocation negative DLBCL treated by R‐CHOP (n = 101), TP53 mutation, BCL2 and BCL6 translocation had no impact on patient survival. The prognosis of MYC translocation positive DLBCL critically depends on the second hit, with TP53 mutations and BCL2 translocation contributing to an adverse prognosis. It is pivotal to investigate both TP53 mutations and BCL2 translocations in MYC translocation positive DLBCL, and to distinguish double‐hit DLBCLs from those with an isolated MYC translocation.

Acquisition of a t(11;14)(q13;q32) in clonal evolution in a follicular lymphoma with a t(14;18)(q32;q21) and t(3;22)(q27;q11.2)

Chromosome translocations involving an immunoglobulin (IG) locus and another gene, either BCL or MYC, are common events in B-cell lymphoma. Occasionally, two IG loci, one with BCL and the other with MYC, are simultaneously involved; such cases are classified as double-hit (DH) lymphomas. These tumors often show intermediate histologic features between those of diffuse large B-cell lymphoma and those of Burkitt lymphoma. Patients with DH lymphoma have a poor prognosis. Rarely, lymphomas in which three IG loci are simultaneously involved with two different BCL genes and MYC have been reported. These cases are classified as triple-hit lymphomas; virtually all these are aggressive tumors with an even worse prognosis. We present here a unique case of follicular lymphoma (FL) with rearranged BCL2, BCL6, and BCL1 (also known as CCND1) genes. Lymphoma cells at first clinical relapse had a complex karyotype that included a t(3;22)(q27;q11) and t(14;18)(q32;q21). About 15 years after initial diagnosis, the lymphoma cells showed clonal cytogenetic evolution and acquired a t(11;14)(q13;q32). This article is the first case report of a low grade B-cell lymphoma that had three lymphoma-associated reciprocal translocations not involving MYC and that had a long indolent clinical course.

Impact of MYC on malignant behavior

MYC, a member of the helix-loop-helix leucine zipper family of nuclear transcription factors, is a potent proto-oncogene primarily identified as the target of the t(8;14)(q24;q32) chromosome translocation in Burkitt lymphoma. Activation of the MYC gene in normal cells both results in enhanced cellular proliferation and up-regulation of pro-apoptotic pathways, reflecting the tight regulation of the molecule in the normal cellular system. In the process of transformation, these secondary inhibitory functions of the MYC molecule have to be overcome through secondary mutations of the MYC gene itself and/or by abrogating the inhibitory effects of physiological regulators and/or repressors of proliferation such as BCL2, BCL6, BLIMP1, or others. Most aggressive lymphomas, therefore, harbor additional oncogenic alterations that cooperate with MYC deregulation, with different alterations identified in human solid or hematological tumors. These alterations are likely to counteract the pro-apoptotic function of MYC. MYC gene alterations in diffuse large B-cell lymphomas and in B-cell lymphomas, unclassifiable, with features intermediate between diffuse large B-cell lymphoma and Burkitt lymphoma are frequently associated with BCL2 or/and BCL6 translocations conferring a very aggressive behavior. This review summarizes inherent factors of the biology and function of MYC important in the process of transformation, especially taking account the interdependence of MYC on various cellular networks that have to be co-deregulated to achieve the full malignant phenotype.

Diagnosis of ‘double hit’ diffuse large B-cell lymphoma and B-cell lymphoma, unclassifiable, with features intermediate between DLBCL and Burkitt lymphoma: when and how, FISH versus IHC

Identification of large B-cell lymphomas that are “extra-aggressive” and may require therapy other than that used for diffuse large B-cell lymphoma, not otherwise specified (DLBCL, NOS), is of great interest. Large B-cell lymphomas with MYC plus BCL2 and/or BCL6 rearrangements, so-called ‘double hit’ (DHL) or ‘triple hit’ (THL) lymphomas, are one such group of cases often recognized using cytogenetic FISH studies. Whether features such as morphologic classification, BCL2 expression, or type of MYC translocation partner may mitigate the very adverse prognosis of DHL/THL is controversial. Classification of the DHL/THL is also controversial, with most either dividing them up between the DLBCL, NOS and B-cell lymphoma, unclassifiable, with features intermediate between DLBCL and Burkitt lymphoma (BCLU) categories or classifying at least the majority as BCLU. The BCLU category itself has many features that overlap those of DHL/THL. Currently, there is growing interest in the use of MYC and other immunohistochemistry either to help screen for DHL/THL or to identify “double-expressor” (DE) large B-cell lymphomas, defined in most studies as having ≥40% MYC+ and ≥50%-70% BCL2+ cells. DE large B-cell lymphomas are generally aggressive, although not as aggressive as DHL/THL, are more common than DHL/THL, and are more likely to have a nongerminal center phenotype. Whether single MYC rearrangements or MYC expression alone is of clinical importance is controversial. The field of the DHL/THL and DE large B-cell lymphomas is becoming more complex, with many issues left to resolve; however, great interest remains in identifying these cases while more is learned about them.

A Double Hit CD10-Negative B-Cell Lymphoma with t(3;8)(q27;q24) Leading to Juxtaposition of the BCL6 and MYC Loci Associated with Good Clinical Outcome

The WHO classification of lymphomas allows for a group of diseases that have features intermediate between those of Burkitt lymphoma and diffuse large B-cell lymphoma. These are a diverse group of diseases whose genetics and clinical course are yet to be fully described. We report an unusual case of high grade B-cell lymphoma, intermediate between DLBCL and BL, lacking CD10 expression in which the chromosomal translocation t(3;8)(q27;q24) was found to be the sole chromosomal abnormality. FISH analysis demonstrated juxtaposition of the BCL6 and MYC loci without obvious involvement of the IGH locus, suggesting constitutive MYC expression due to promoter substitution. The patient responded to intensive chemotherapy and remains in remission two years after finishing therapy.

Aggressive B-cell lymphomas with translocations involving BCL6 and MYC have distinct clinical-pathologic characteristics

OBJECTIVES

Recently described, aggressive B-cell lymphomas with genetic abnormalities involving MYC and BCL2 have been shown to have a poor prognosis when treated with regimens for diffuse large B-cell lymphomas. Similar data on cases with concurrent MYC and BCL6 translocation are still scant. Moreover, little is known regarding the morphologic and immunophenotypic characteristics of these cases, which further complicates their identification. This study describes six cases of aggressive B-cell lymphoma with translocations involving MYC and BCL6.

METHODS

Six cases of large B-cell lymphoma with translocation involving MYC and BCL6 confirmed by fluorescence in situ were identified. The morphologic, immunophenotypic, and clinical features of the cases were examined.

RESULTS

All the patients were older women, and in 50% of cases, the presentation was extranodal. In two cases, the liver was involved at presentation. A starry-sky pattern was a constant feature of the cases in which the morphology could be reliably assessed. Five of six cases had an immunophenotype corresponding to the germinal center B cells, and only one was positive for BCL2, an immunophenotype reminiscent of that of Burkitt lymphoma.

CONCLUSIONS

B-cell lymphomas with translocations involving MYC and BCL6 have morphologic and immunophenotypic features suggestive of Burkitt lymphoma or gray zone lymphoma, and they tend to be diagnosed mainly in women, often in extranodal locations.

Large B-cell lymphoma of the base of the tongue and oral cavity: a practical approach to identifying prognostically important subtypes

OBJECTIVE

The aim of this study is to illustrate a practical approach to the identification of prognostically important subtypes of large B-cell lymphomas.

STUDY DESIGN

Twenty-six cases of large B-cell lymphoma in the base of the tongue and oral cavity were retrieved from 2003 through 2012. All cases were classified based on the 2008 World Health Organization criteria. Hematoxylin-eosin-stained sections, immunohistochemical stains, flow cytometric immunophenotypic data, and fluorescence in situ hybridization studies were performed and evaluated.

RESULTS

Four different subtypes of large B-cell lymphoma were identified: pleomorphic variant mantle cell lymphoma, Epstein-Barr virus-positive diffuse large B-cell lymphoma of the elderly, diffuse large B-cell lymphoma not otherwise specified, and B-cell lymphoma unclassifiable with features intermediate between diffuse large B-cell lymphoma and Burkitt lymphoma, including a case of double-hit lymphoma.

CONCLUSIONS

Diverse subtypes of large B-cell lymphoma were identified in the base of tongue and oral cavity, and illustrate a practical approach to recognizing prognostically important lymphoma subtypes.

Current perspectives in genetics of "double-hit" lymphoma with possible clinical implications

This article reviews particular subgroup of B-cell lymphoma, called "double-hit" lymphoma (DHL) because of its distinct aberrations-related genes influencing various processes such as apoptosis, differentiation, and proliferation. Recent studies indicate that tumorigenesis is a complex process involving multiple genes, genetic abnormalities, including gene mutations, deletions, and chromosomal alterations. Chromosomal aberrations are not affecting only basic cellular life preserving activities such as cell proliferation, differentiation, apoptosis, and signal transduction, but are also indispensible for evaluation of lymphoma occurrence, progression, and prognosis as well differential diagnosis and other aspects assessment. DHL is group accompanied by IGH-BCL2 and MYC rearrangement, behaving highly aggressively, with a complex and distinct karyotype which can not be extrapolated solely by morphological pathological assessment, since it has not been entirely characteristic. Therefore, we are reviewing possible effects of multiple genetic rearrangements, particular genes mutations, and developing hypothesis due which pathophysiology mechanisms DHL accomplish synergistic malignant potential.

Management of B-cell non-Hodgkin lymphoma in Asia: resource-stratified guidelines

Treatment of B-cell non-Hodgkin lymphomas has undergone substantial developments in the past 10 years. The introduction of rituximab has greatly improved survival outcomes in patients. Clinical practice guidelines based on current evidence have been developed to provide recommendations for standard treatment approaches. However, guidelines do not take into account resource limitations in resource-poor countries. The huge disparities in economy, health-care infrastructure, and access to novel drugs between Asian countries can hinder the delivery of optimum care to patients with lymphoma in Asia. We outline guidelines appropriate to different levels of health-care resources and expertise, aiming to provide advice on diagnosis and treatment, unify interpretation of results, and allow the design of future studies in Asia. In this resource-adapted consensus, we summarise recommendations for diagnosis, staging, risk stratification, and treatment of common B-cell non-Hodgkin lymphomas in Asia.

Biological characterization of adult MYC-translocation-positive mature B-cell lymphomas other than molecular Burkitt lymphoma

Chromosomal translocations affecting the MYC oncogene are the biological hallmark of Burkitt lymphomas but also occur in a subset of other mature B-cell lymphomas. If accompanied by a chromosomal break targeting the BCL2 and/or BCL6 oncogene these MYC translocation-positive (MYC(+)) lymphomas are called double-hit lymphomas, otherwise the term single-hit lymphomas is applied. In order to characterize the biological features of these MYC(+) lymphomas other than Burkitt lymphoma we explored, after exclusion of molecular Burkitt lymphoma as defined by gene expression profiling, the molecular, pathological and clinical aspects of 80 MYC-translocation-positive lymphomas (31 single-hit, 46 double-hit and 3 MYC(+)-lymphomas with unknown BCL6 status). Comparison of single-hit and double-hit lymphomas revealed no difference in MYC partner (IG/non-IG), genomic complexity, MYC expression or gene expression profile. Double-hit lymphomas more frequently showed a germinal center B-cell-like gene expression profile and had higher IGH and MYC mutation frequencies. Gene expression profiling revealed 130 differentially expressed genes between BCL6(+)/MYC(+) and BCL2(+)/MYC(+) double-hit lymphomas. BCL2(+)/MYC(+) double-hit lymphomas more frequently showed a germinal center B-like gene expression profile. Analysis of all lymphomas according to MYC partner (IG/non-IG) revealed no substantial differences. In this series of lymphomas, in which immunochemotherapy was administered in only a minority of cases, single-hit and double-hit lymphomas had a similar poor outcome in contrast to the outcome of molecular Burkitt lymphoma and lymphomas without the MYC break. Our data suggest that, after excluding molecular Burkitt lymphoma and pediatric cases, MYC(+) lymphomas are biologically quite homogeneous with single-hit and double-hit lymphomas as well as IG-MYC and non-IG-MYC(+) lymphomas sharing various molecular characteristics.

Follicular lymphoma-like B cells of uncertain significance (in situ follicular lymphoma) may infrequently progress, but precedes follicular lymphoma, is associated with other overt lymphomas and mimics follicular lymphoma in flow cytometric studies

In situ follicular lymphoma, more recently known as follicular lymphoma-like B cells of uncertain/undetermined significance is well accepted. However, the morphological criteria have evolved since it was first described and data are limited and conflicting regarding its clinical implications and whether the extent of involvement predicts an association with overt lymphoma. It is also unknown how often it will be identified by flow cytometric studies and how often it precedes overt follicular lymphomas. A multiparameter study of 31 biopsies with follicular lymphoma-like B cells of uncertain significance and 4 'benign' lymph node biopsies that preceded an overt follicular lymphoma was, therefore, performed. Fifty-two percent of biopsies with follicular lymphoma-like B cells were associated with a prior or concurrent lymphoma but only 6% subsequently developed lymphoma (median follow up 26 months). Neither the number, proportion or density of BCL2(+) germinal centers were associated with overt follicular lymphoma/diffuse large B-cell lymphoma. Flow cytometric studies identified follicular lymphoma-like B cells in 8 of 15 evaluable cases. The proportion but not the absolute number of BCL2(+) germinal centers was associated with the likelihood of positive flow cytometric studies (P<0.01). All 4 'benign' biopsies that preceded an overt follicular lymphoma demonstrated follicular lymphoma-like B cells. Thus, although few patients with follicular lymphoma-like B cells of uncertain significance progress within the follow-up period, it at least precedes many follicular lymphomas. The extent of involvement does not predict the occurrence of prior or concurrent lymphomas. Flow cytometric studies demonstrating follicular lymphoma-like B cells must not be over-interpreted as they may only reflect follicular lymphoma-like B cells.

Understanding MYC-driven aggressive B-cell lymphomas: pathogenesis and classification

MYC is a potent oncogene initially identified as the target of the t(8;14)(q24;q32) chromosome translocation in Burkitt lymphoma. MYC gene alterations have been identified in other mature B-cell neoplasms that are usually associated with an aggressive clinical behavior. Most of these tumors originate in cells that do not normally express MYC protein. The oncogenic events leading to MYC up-regulation seem to overcome the inhibitory effect of physiological repressors such as BCL6 or BLIMP1. Aggressive lymphomas frequently carry additional oncogenic alterations that cooperate with MYC dysregulation, likely counteracting its proapoptotic function. The development of FISH probes and new reliable antibodies have facilitated the study of MYC gene alterations and protein expression in large series of patients, providing new clinical and biological perspectives regarding MYC dysregulation in aggressive lymphomas. MYC gene alterations in large B-cell lymphomas are frequently associated with BCL2 or BCL6 translocations conferring a very aggressive behavior. Conversely, MYC protein up-regulation may occur in tumors without apparent gene alterations, and its association with BCL2 overexpression also confers a poor prognosis. In this review, we integrate all of this new information and discuss perspectives, challenges, and open questions for the diagnosis and management of patients with MYC-driven aggressive B-cell lymphomas.

Understanding MYC-driven aggressive B-cell lymphomas: pathogenesis and classification

MYC is a potent oncogene initially identified as the target of the t(8;14)(q24;q32) chromosome translocation in Burkitt lymphoma. MYC gene alterations have been identified in other mature B-cell neoplasms that are usually associated with an aggressive clinical behavior. Most of these tumors originate in cells that do not normally express MYC protein. The oncogenic events leading to MYC up-regulation seem to overcome the inhibitory effect of physiological repressors such as BCL6 or BLIMP1. Aggressive lymphomas frequently carry additional oncogenic alterations that cooperate with MYC dysregulation, likely counteracting its proapoptotic function. The development of FISH probes and new reliable antibodies have facilitated the study of MYC gene alterations and protein expression in large series of patients, providing new clinical and biological perspectives regarding MYC dysregulation in aggressive lymphomas. MYC gene alterations in large B-cell lymphomas are frequently associated with BCL2 or BCL6 translocations conferring a very aggressive behavior. Conversely, MYC protein up-regulation may occur in tumors without apparent gene alterations, and its association with BCL2 overexpression also confers a poor prognosis. In this review, we integrate all of this new information and discuss perspectives, challenges, and open questions for the diagnosis and management of patients with MYC-driven aggressive B-cell lymphomas.