Chromosomal analyses of 52 cases of follicular lymphoma with t(14;18), including blastic/blastoid variant

Targeting PRL phosphatases in hematological malignancies

INTRODUCTION

Phosphatase of regenerating liver (PRL) family proteins, also known as protein tyrosine phosphatase 4A (PTP4A), have been implicated in many types of cancers. The PRL family of phosphatases consists of three members, PRL1, PRL2, and PRL3. PRLs have been shown to harbor oncogenic potentials and are highly expressed in a variety of cancers. Given their roles in cancer progression and metastasis, PRLs are potential targets for anticancer therapies. However, additional studies are needed to be performed to fully understand the roles of PRLs in blood cancers.

AREAS COVERED

In this review, we will summarize recent studies of PRLs in normal and malignant hematopoiesis, the role of PRLs in regulating various signaling pathways, and the therapeutic potentials of targeting PRLs in hematological malignancies. We will also discuss how to improve current PRL inhibitors for cancer treatment.

EXPERT OPINION

Although PRL inhibitors show promising therapeutic effects in preclinical studies of different types of cancers, moving PRL inhibitors from bench to bedside is still challenging. More potent and selective PRL inhibitors are needed to target PRLs in hematological malignancies and improve treatment outcomes.

MYC single-hit large B-cell lymphoma: clinicopathologic difference from MYC-negative large B-cell lymphoma and MYC double-hit/triple-hit lymphoma

MYC-rearranged large B-cell lymphoma with BCL2 and/or BCL6 rearrangement, double-hit (DH) or triple-hit (TH) lymphoma, is associated with poor survival after standard treatment. To investigate the clinical impact of single-hit (SH) MYC rearrangement, we analyzed 241 cases of diffuse large B-cell lymphoma (DLBCL) for MYC, BCL2, and BCL6 rearrangement by fluorescence in situ hybridization. Fifty-five of 241 (22.8%) cases showed MYC rearrangements. Twenty-three cases were diagnosed as DLBCL; 18 as high-grade B-cell lymphoma (HGBCL)-DH; 3 as HGBCL-TH; and 11 as HGBCL, not otherwise specified. Both DH and TH lymphomas showed high-grade morphology (P = 0.002), higher stage (P = 0.022), and more frequent germinal center B-cell-like phenotype (P = 0.008). SH lymphomas displayed high-grade morphology (P = 0.002) but were not different from MYC-negative lymphomas in cell of origin, clinical stage, international prognostic index (IPI), or extranodal involvement. Patients with DH/TH lymphomas had worse overall survival (OS) (P = 0.016) and progression-free survival (PFS) (P < 0.001), while OS and PFS of SH lymphomas were not different from those of MYC-negative lymphomas. There was no survival difference between cases of BCL2 and BCL6 rearrangements. Poorer prognostic factors included higher ECOG class, higher IPI, and DH or TH translocation for OS, and higher IPI and DH or TH translocation for PFS. Higher IPI was an independent prognostic factor for OS and PFS. In conclusion, large B-cell lymphomas with single MYC rearrangement showed high-grade morphology but were otherwise not different from MYC-negative lymphomas.

Simultaneous Discordant B-Lymphoblastic Lymphoma and Follicular Lymphoma

OBJECTIVES

We report a rare case of B-lymphoblastic lymphoma (B-LBL) and low-grade follicular lymphoma (FL) identified concurrently in biopsies from different sites at the initial diagnosis in a 39-year-old man. The clonal relationship between the 2 histologic subtypes was investigated.

METHODS

A diagnosis of FL grade 1/2 (low grade) was made by bone marrow (BM) biopsy. B-LBL was identified in biopsies from the testis and pancreas. Cytogenetic and molecular analyses were performed to investigate their clonal relationship.

RESULTS

Interphase fluorescence in situ hybridization analyses and G-banding karyotype analyses identified the BCL2-IGH and MYC-IGH translocation in tumor cells from both the BM and testis. The tumor cells from the BM and testis shared the same IGH VDJ usage and a high degree of somatic mutations. These findings suggest that acquisition of MYC gene rearrangement is a critical event for lymphoblastic transformation of FL. Of note, the presence of intraclonal diversity in the B-LBL sample further suggests an earlier or concurrent event of MYC translocation than the somatic IGH mutation in the germinal center and the dedifferentiation of lymphoma cells to a precursor stage of B-cell development.

CONCLUSIONS

B-lymphoblastic transformation of FL can occur with MYC gene rearrangement.

[The role of translocations involving c-MYC/8q24, BCL2/18q21 and/or BCL6/3q27 genes in patients with follicular lymphoma. Retrospective analysis of single - centre data]

Aim of the issue was to compare clinical characteristics and treatment results of patients with follicular lymphoma (FL) with translocations involving loci of c-MYC/8q24, BCL2/18q21 and/or BCL6/3q27 genes and patients with high - grade B-cell lymphoma [High - grade B-cell lymphoma (HGBL), double - hit (DH)]. Materials and methods. Since 2004 to 2017 years in National Research Center for Hematology 12 patients with high - grade B-cell lymphoma double - hit (HGBL DH) and 6 FL patients with translocations involving c-MYC and BCL2 and/or BCL6 had been treated. We performed a comparative analysis of clinical characterisctics in both groups. As primary endpoints was assessed frequency of complete remission (CR) or progressive disease (PD); as secondary endpoints - overall (OS) and event - free survival (EFS). Results. 5 patients with HGBL DH had c-MYC/BCL6, 7 - c-MYC/BCL2 rearrangements; 2 patients with FL had c-MYC/BCL2, 3 - c-MYC/BCL6, 1 - c-MYC/BCL2/BCL6 rearrangements. FL was represented by grade 3A in 2, grade 3B - in 4 cases, 3 of them had large - cell transformation. In HGBL DH and FL patients had no significant differences in clinical characteristics. The majority of patients had a widespread tumour, increased LDH activity, high frequency of extranodal and bone marrow involvement. Ki-67 expression level was lower in patients with FL (p.

Prognostic impact of trisomy 21 in follicular lymphoma

The chromosomal abnormalities associated with follicular lymphoma (FL) prognosis are not fully elucidated. Here, we evaluated the pattern of chromosomal abnormalities in FL, and clarified the correlations between the cytogenetic features and clinical outcome. Cytogenetic analysis was performed using standard methods of Giemsa-banding at diagnosis for 201 FL patients admitted to our hospitals between 2001 and 2013. The identified chromosomal abnormalities were: t(14;18)(q32;q21) (59·2%), +X (17·9%), del(6)(q)/-6 (16·9%), +7 (14·4%), abnormality of 1q12-21/1q (12·9%), del(13)(q)/-13 (11·9%), abnormality of 3q27 (10·4%), abnormality of 10q22-24 (10·0%), +12/dup(12)(q) (10·0%), abnormality of 1p21-22/1p (9·0%), +18 (9·0%), del(17)(p)/-17 (5·0%), and a complex karyotype (54·7%). Patients with trisomy 21 had a significantly shorter progression-free survival (P = 0·00171) and overall survival (OS) (P < 0·001) than those without trisomy 21; additionally, patients with trisomy 21 in the rituximab-treated cohort also had a significantly shorter OS (P = 0·000428). Multivariate analysis identified trisomy 21 as an independent risk factor in our cohorts with or without t(14;18) (P = 0·015). In conclusion, the presence of trisomy 21 was an independent risk factor for in FL. Chromosomal analysis of FL patients at diagnosis can provide useful information about their expected survival.

Advances in pathological understanding of high-grade B cell lymphomas

INTRODUCTION

The designation high-grade B-cell lymphoma (HGBL) has been incorporated into the 2016 Revision of the WHO classification of lymphoid neoplasms and includes two types: (1) HGBL, not otherwise specified; and (2) HGBL with MYC and BCL2 and/or BCL6 rearrangements, also known as double or triple hit lymphoma (DHL/THL). These categories of lymphomas represent 1-2% of non-Hodgkin lymphomas and a considerable portion of DLBCL patients who are primary refractory to R-CHOP therapy. It corresponds to the designation 'B-cell lymphoma, unclassifiable, with features intermediate between DLBCL and Burkitt lymphoma' in the 2008 WHO classification. Areas covered: This paper provides an update of HGBL, focusing on their pathologic features, prognosis, and diagnostic workup. It highlights advances in our understanding of DHL/THL. Expert commentary: The diagnosis relies on FISH testing and the major controversial question is when to perform it to diagnose virtually all DHL/THL cases, but also being cost effective. Currently there is no consensus. Considering the high refractory rate of these patients to standard R-CHOP induction, the authors recommend FISH testing in all newly diagnosed large B-cell lymphoma by using our stepwise test strategy. With the progress of molecular genetics, the prognosis will be further stratified and HGBL-NOS maybe further evolve too.

A leukemic double-hit follicular lymphoma associated with a complex variant translocation, t(8;14;18)(q24;q32;q21), involving BCL2, MYC, and IGH

Double-hit lymphoma (DHL) is defined as lymphoma with concurrent BCL2 and MYC translocations. While the most common histological subtype of DHL is diffuse large B-cell lymphoma, the present patient had leukemic follicular lymphoma (FL). A 52-year-old man was admitted to our hospital due to general fatigue and cervical and inguinal lymph node swelling. The patient was leukemic and the pathological diagnosis of the inguinal lymph node was FL grade 1. Chromosomal analysis revealed a complex karyotype including a rare three-way translocation t(8;14;18)(q24;q32;q21) involving the BCL2, MYC, and IGH genes. Based on a combination of fluorescence in situ hybridization (FISH), using BCL2, MYC and IGH, and spectral karyotyping (SKY), the karyotype was interpreted as being the result of a multistep mechanism in which the precursor B-cell gained t(14;18) in the bone marrow and acquired a translocation between der(14)t(14;18) and chromosome 8 in the germinal center, resulting in t(8;14;18). The pathological diagnosis was consistently FL, not only at presentation but even after a second relapse. The patient responded well to standard chemotherapies but relapsed after a short remission. This patient is a unique case of leukemic DH-FL with t(8;14;18) that remained in FL even at a second relapse.

Protein Tyrosine Phosphatase PRL2 Mediates Notch and Kit Signals in Early T Cell Progenitors

The molecular pathways regulating lymphoid priming, fate, and development of multipotent bone marrow hematopoietic stem and progenitor cells (HSPCs) that continuously feed thymic progenitors remain largely unknown. While Notch signal is indispensable for T cell specification and differentiation, the downstream effectors are not well understood. PRL2, a protein tyrosine phosphatase that regulates hematopoietic stem cell proliferation and self-renewal, is highly expressed in murine thymocyte progenitors. Here we demonstrate that protein tyrosine phosphatase PRL2 and receptor tyrosine kinase c-Kit are critical downstream targets and effectors of the canonical Notch/RBPJ pathway in early T cell progenitors. While PRL2 deficiency resulted in moderate defects of thymopoiesis in the steady state, de novo generation of T cells from Prl2 null hematopoietic stem cells was significantly reduced following transplantation. Prl2 null HSPCs also showed impaired T cell differentiation in vitro. We found that Notch/RBPJ signaling upregulated PRL2 as well as c-Kit expression in T cell progenitors. Further, PRL2 sustains Notch-mediated c-Kit expression and enhances stem cell factor/c-Kit signaling in T cell progenitors, promoting effective DN1-DN2 transition. Thus, we have identified a critical role for PRL2 phosphatase in mediating Notch and c-Kit signals in early T cell progenitors. Stem Cells 2017;35:1053-1064.

Detection of chromosomal abnormalities by G-banding and prognostic impact in follicular lymphoma in the rituximab era

Disease-specific cytogenetic abnormalities involving BCL2 gene rearrangement frequently co-exist with other cytogenetic abnormalities, contributing to disease progression in follicular lymphoma (FL). In the present study, we retrospectively investigated the prognostic impact of BCL2-unrelated cytogenetic abnormalities in FL. Of 139 consecutively diagnosed patients with FL at two independent institutes, metaphase spreads of tumor cells were obtained for use in G-banding analysis in 77 patients. The recurrent additional cytogenetic abnormalities included chromosome gains +5 (n = 8), +7 (n = 16), +12 (n = 10), and +X (n = 12), and losses -8 (n = 7), -13 (n = 12) -15 (n = 7), and 6q- (n = 7). While -15 was associated with shorter progression-free survival (PFS) in all 77 analyzed patients with evaluable G-banding results (p = 0.04), this negative impact was not evident in 42 patients treated using an R-CHOP-like regimen as first-line treatment. By contrast, 6q- was predictive for shorter PFS in patients who were initially treated with R-CHOP-like regimens without maintenance therapy (p < 0.01), while this negative impact was not evident in all 77 patients with evaluable G-banding results. These results suggest the presence of a molecular region in chromosome 6q that is responsible for the shorter PFS following R-CHOP-like chemotherapy.

Current challenges and novel treatment strategies in double hit lymphomas

High-grade B-cell lymphomas with recurrent chromosomal break points have been termed 'double hit lymphoma' (DHL). The most commonly seen DHL is diffuse large B-cell lymphoma (DLBCL) with t(14;18) and t(8;14) or t(8;22) resulting in overexpression of BCL2 and MYC, respectively. The increased proliferation due to MYC overexpression, without the ability for an apoptotic brake as a result of BCL2 overexpression, results in 'the perfect storm of oncogenesis'. Thus this disease presents a number of diagnostic and therapeutic challenges for the hematologist. The first and foremost challenge is to recognize the DHL. As different morphological entities can be affected it is incumbent on pathologists and clinicians to maintain a high index of suspicion especially in disease that appears unusually aggressive or refractory to therapy. Diagnosis by fluorescence in situ hybridization (FISH) is a sensitive and specific method for detection of the disease but is time-consuming and expensive. While detection by immunohistochemistry (IHC) is sensitive and correlates with survival, standardized methods for this are not widely agreed upon. The second and equally important challenge in DHL is optimizing clinical outcome in a group of patients for whom the prognosis is widely regarded as poor. While improvements have been achieved by dose escalating standard chemotherapeutic regimens, many patients continue to do badly. Furthermore as a disease of aging many patients are unsuitable for dose-intensive chemotherapy regimens. There are now multiple novel targeted agents in various stages of clinical development that offer hope for better outcomes without undue toxicity. Among the most exciting of these developments include specific inhibitors of both BCL2 and MYC.

Phosphatase of regenerating liver in hematopoietic stem cells and hematological malignancies

The phosphatases of regenerating liver (PRLs), consisting PRL1, PRL2 and PRL3, are dual-specificity protein phosphatases that have been implicated as biomarkers and therapeutic targets in several solid tumors. However, their roles in hematological malignancies are largely unknown. Recent findings demonstrate that PRL2 is important for hematopoietic stem cell self-renewal and proliferation. In addition, both PRL2 and PRL3 are highly expressed in some hematological malignancies, including acute myeloid leukemia (AML), chronic myeloid leukemia (CML), multiple myeloma (MM) and acute lymphoblastic leukemia (ALL). Moreover, PRL deficiency impairs the proliferation and survival of leukemia cells through regulating oncogenic signaling pathways. While PRLs are potential novel therapeutic targets in hematological malignancies, their exact biological function and cellular substrates remain unclear. This review will discuss how PRLs regulate hematopoietic stem cell behavior, what signaling pathways are regulated by PRLs, and how to target PRLs in hematological malignancies. An improved understanding of how PRLs function and how they are regulated may facilitate the development of PRL inhibitors that are effective in cancer treatment.

PRL2/PTP4A2 phosphatase is important for hematopoietic stem cell self-renewal

Hematopoietic stem cell (HSC) self-renewal is tightly controlled by cytokines and other signals in the microenvironment. While stem cell factor (SCF) is an early acting cytokine that activates the receptor tyrosine kinase KIT and promotes HSC maintenance, how SCF/KIT signaling is regulated in HSCs is poorly understood. The protein tyrosine phosphatase 4A (PTP4A) family (aka PRL [phosphatase of regenerating liver] phosphatases), consisting of PTP4A1/PRL1, PTP4A2/PRL2, and PTP4A3/PRL3, represents an intriguing group of phosphatases implicated in cell proliferation and tumorigenesis. However, the role of PTP4A in hematopoiesis remains elusive. To define the role of PTP4A in hematopoiesis, we analyzed HSC behavior in Ptp4a2 (Prl2) deficient mice. We found that Ptp4a2 deficiency impairs HSC self-renewal as revealed by serial bone marrow transplantation assays. Moreover, we observed that Ptp4a2 null hematopoietic stem and progenitor cells (HSPCs) are more quiescent and show reduced activation of the AKT and ERK signaling. Importantly, we discovered that the ability of PTP4A2 to enhance HSPC proliferation and activation of AKT and ERK signaling depends on its phosphatase activity. Furthermore, we found that PTP4A2 is important for SCF-mediated HSPC proliferation and loss of Ptp4a2 decreased the ability of oncogenic KIT/D814V mutant in promoting hematopoietic progenitor cell proliferation. Thus, PTP4A2 plays critical roles in regulating HSC self-renewal and mediating SCF/KIT signaling.

Follicular lymphoma grade 3: review and updates

Follicular lymphoma (FL), Grade 3, is recognized as a distinct entity in the World Health Organization classification of lymphoma. It is further classified into Grade 3a and Grade 3b depending on the Bernard cell counting system and percentage of centroblasts. Grade 3 has molecular and genetic characteristics that distinguish it from other grades of FL. There is confusion and misunderstanding about the natural history and clinical course of Grade 3a and 3b because some studies indicate them as having indolent behavior and others describe more aggressive biology. The purpose of this article is to understand the concept of Grade 3 FL, especially the fundamental differences between Grade 3a and Grade 3b FL. Grade 3 FL is still an evolving subclass in FL and the practicing physician should understand the aggressive nature of Grade 3b, which typically requires timely attention, compared with Grade 3a. Grade 3a FL has more indolent characteristics but can possibly progress to Grade 3b and/or transform to diffuse large B-cell lymphoma at a future time. Nevertheless, large prospective studies are missing for an optimal evidence-based management approach for patients with Grade 3 FL at this time.

High-grade B cell lymphoma, unclassifiable, with blastoid features: an unusual morphological subgroup associated frequently with BCL2 and/or MYC gene rearrangements and a poor prognosis

AIMS

A subset of B cell lymphomas with blastoid features do not fit either as B lymphoblastic lymphoma/leukaemia or blastoid mantle cell lymphoma. Their classification is challenging, even with complete clinicopathological and genetic information. At a haematopathology workshop, experts had suggested the term 'high-grade B cell lymphoma, unclassifiable, with blastoid features', and recommended further studies.

METHODS AND RESULTS

We describe the clinicopathological, immunophenotypic and cytogenetic findings of 24 high-grade B cell lymphomas, unclassifiable, with blastoid features. Fifteen patients presented de novo and seven patients had a history of lymphoma. Twenty patients (83%) presented with nodal disease. All tumours expressed pan-B cell antigens and 17 (89%) of 19 tumours assessed had a germinal centre B cell immunophenotype. Ten (63%) of 16 tumours assessed by fluorescence in-situ hybridization (FISH) had MYC rearrangement, 13 of 18 (72%) carried IGH-BCL2 and nine of 15 (60%) had both (double-hit lymphoma). The median overall survival was 1.1 years. Using 2008 World Health Organization criteria, 15 cases were classified as B cell lymphoma, unclassifiable, with features intermediate between diffuse large B cell lymphoma (DLBCL) and Burkitt lymphoma, and nine as DLBCL, small centroblastic variant.

CONCLUSION

High-grade B cell lymphomas, unclassifiable, with blastoid features are clinically aggressive with poor survival. Most neoplasms have a germinal centre B cell phenotype. MYC rearrangements and IGH-BCL2 are common, and ~60% are double-hit lymphomas.

Biology of double-hit B-cell lymphomas

PURPOSE OF REVIEW

Mature B-cell lymphomas bearing concurrent chromosomal rearrangement of MYC/8q24 and BCL2/18q21 are associated with an aggressive clinical course and resistance to conventional chemotherapy. This review summarizes the recent literature regarding the clinical and pathologic features of double-hit lymphomas and outlines current questions about the most accurate and inclusive definition of the disease.

RECENT FINDINGS

Comprehensive evaluation of large series of aggressive mature B-cell neoplasms reveals recurrent chromosomal aberrations in the majority of cases. A subset of these lymphomas harbors multiple rearrangements, including MYC/8q24 in combination with BCL2/18q21 and/or BCL6/3q27, and displays a particularly aggressive clinical course. Recent data suggest that consideration of additional features, such as copy number alteration, quantitative protein expression, and biologic pathway activation may be important in deriving a more accurate definition of double-hit lymphoma. Despite the poor prognosis associated with this subset of lymphomas, there remains no evidence for a risk-adapted treatment strategy and no clinical, pathologic, or genetic factors that predict response to therapy.

SUMMARY

Double-hit lymphoma remains an incompletely characterized disease entity. Large, multicenter studies are needed to define relevant clinical, genetic, and pathologic variables and to characterize appropriate risk-adapted treatment strategies.

Follicular lymphoma grade 3B is a distinct neoplasm according to cytogenetic and immunohistochemical profiles

BACKGROUND

According to the current World Health Organization Classification of Lymphoid Tumours, follicular lymphoma is subclassified into three grades according to the number of centroblasts. Follicular lymphoma grade 3 can be further divided into types A and B. Almost all available genetic data on grade 3B follicular lymphomas have been generated from tumors with an additional diffuse large B-cell lymphoma component. The purely follicular type of follicular lymphoma grade 3B is a rare neoplasm.

DESIGN AND METHODS

We performed a detailed immunohistochemical (CD10, IRF4/MUM1, BCL2, Ig light chains) and genetic (translocations of BCL2, BCL6, MYC, IRF4) characterization of the largest series of purely follicular cases of grade 3B follicular lymphoma available to date, comprising 23 tumor samples. We also included 25 typical grade 1 or 2 follicular lymphomas, 9 follicular lymphomas with large centrocytes and/or high proliferation indices (FL/LCC), 12 cases of follicular lymphoma grade 3A, 16 cases of diffuse large B-cell lymphoma/follicular lymphoma grade 3B and 15 follicular lymphomas in which a straightforward distinction between grades 3A and 3B was not possible.

RESULTS

Translocations affecting BCL2 and BCL6 genes are rare in grade 3B follicular lymphomas (2/23, 9% and 4/23, 17%) when compared with grade 1 or 2 follicular lymphomas (22/25, 88%, P<0.001 and 0/25, P<0.05), FL/LCC (7/9, 78%, P<0.001 and 2/9, 22%), grade 3A follicular lymphomas (7/12, 58%, P<0.01 and 2/12, 17%), unclassified grade 3 follicular lymphomas (6/15, 40% and 2/15, 13%) and diffuse large B-cell lymphoma/follicular lymphoma grade 3B (2/16, 13% and 8/16, 50%, P<0.05). MYC translocations were detected occasionally in FL/LCC, follicular lymphoma grade 3B, and diffuse large B-cell lymphoma/follicular lymphoma grade 3B (13%-22%), but not in grade 1, 2 or 3A follicular lymphomas (P<0.05 when compared with follicular lymphoma grade 3B). Both follicular lymphoma grade 3B and diffuse large B-cell lymphoma/follicular lymphoma grade 3B were enriched in samples with a CD10(-)IRF4/MUM1(+) immunophenotype (8/19, 42% and 7/16, 44%), with the vast majority of them lacking BCL2 translocations. In contrast, 42/46 grade 1 or 2 follicular lymphomas, FL/LCC and grade 3A follicular lymphomas were CD10(+) (91%) while 0/46 expressed IRF4/MUM1. None of the tumor samples tested with increased IRF4/MUM1-expression harbored a translocation of the IRF4 gene locus.

CONCLUSIONS

Our results show that grade 3B follicular lymphomas form a distinct category of follicular lymphomas with infrequent BCL2 and BCL6 translocations, while grades 1, 2 and 3A follicular lymphomas and FL/LCC display homogeneous features with frequent BCL2 translocations and a CD10(+)IRF4/MUM1(-) immunophenotype.

Double-hit B-cell lymphomas

In many B-cell lymphomas, chromosomal translocations are biologic and diagnostic hallmarks of disease. An intriguing subset is formed by the so-called double- hit (DH) lymphomas that are defined by a chromosomal breakpoint affecting the MYC/8q24 locus in combination with another recurrent breakpoint, mainly a t(14;18)(q32;q21) involving BCL2. Recently, these lymphomas have received increased attention, which contributed to the introduction of a novel category of lymphomas in the 2008 WHO classification, "B cell lymphoma unclassifiable with features intermediate between DLBCL and BL." In this review we explore the existing literature for the most recurrent types of DH B-cell lymphomas and the involved genes with their functions, as well as their pathology and clinical aspects including therapy and prognosis. The incidence of aggressive B-cell lymphomas other than Burkitt lymphoma with a MYC breakpoint and in particular a double hit is difficult to assess, because screening by methods like FISH has not been applied on large, unselected series, and the published cytogenetic data may be biased to specific categories of lymphomas. DH lymphomas have been classified heterogeneously but mostly as DLBCL, the majority having a germinal center phenotype and expression of BCL2. Patients with DH lymphomas often present with poor prognostic parameters, including elevated LDH, bone marrow and CNS involvement, and a high IPI score. All studies on larger series of patients suggest a poor prognosis, also if treated with RCHOP or high-intensity treatment modalities. Importantly, this poor outcome cannot be accounted for by the mere presence of a MYC/8q24 breakpoint. Likely, the combination of MYC and BCL2 expression and/or a related high genomic complexity are more important. Compared to these DH lymphomas, BCL6(+)/MYC(+) DH lymphomas are far less common, and in fact most of these cases represent BCL2(+)/BCL6(+)/MYC(+) triple-hit lymphomas with involvement of BCL2 as well. CCND1(+)/MYC(+) DH lymphomas with involvement of 11q13 may also be relatively frequent, the great majority being classified as aggressive variants of mantle cell lymphoma. This suggests that activation of MYC might be an important progression pathway in mantle cell lymphoma as well. Based on clinical significance and the fact that no other solid diagnostic tools are available to identify DH lymphomas, it seems advisable to test all diffuse large B-cell and related lymphomas for MYC and other breakpoints.

Genomic alterations reveal potential for higher grade transformation in follicular lymphoma and confirm parallel evolution of tumor cell clones

Our aim was to examine the genetics of clonal evolution in follicular lymphoma (FL) and to identify genetic alterations associated with disease progression. A total of 100 biopsies from 44 patients diagnosed with t(14;18)-positive FL were examined by array comparative genomic hybridization. In 20 patients the patterns of somatic hypermutations (SHMs) in the variable region of heavy chain gene were additionally analyzed. Gain of chromosome X in male samples was a marker for poor outcome (P < .01). Gains involving chromosome 2, 3q, and 5 were exclusively present in FL biopsies from cases with higher grade transformation and were among the copy number alterations (CNAs) associated with inferior survival. Although we noted a trend for increasing genomic complexity in initial versus late FL samples, the overall frequencies of CNAs in initial and late FL biopsies showed a surprisingly stable pattern through the course of the disease. In 27 of cases the initial samples harbored CNAs that were absent in relapse samples, indicating that tumor cell clones at relapse were not direct descendants of initially dominating clones. The pattern of SHMs confirmed parallel development of tumor cell clones in 14 cases. Our findings support the hypothesis of common progenitor cells in FL.

B-cell lymphomas with concurrent IGH-BCL2 and MYC rearrangements are aggressive neoplasms with clinical and pathologic features distinct from Burkitt lymphoma and diffuse large B-cell lymphoma

B-cell lymphomas with concurrent IGH-BCL2 and MYC rearrangements, also known as "double-hit" lymphomas (DHL), are rare neoplasms characterized by highly aggressive clinical behavior, complex karyotypes, and a spectrum of pathologic features overlapping with Burkitt lymphoma (BL), diffuse large B-cell lymphoma (DLBCL) and B-lymphoblastic lymphoma/leukemia (B-LBL). The clinical and pathologic spectrum of this rare entity, including comparison to other high-grade B-cell neoplasms, has not been well defined. We conducted a retrospective analysis of clinical and pathologic features of 20 cases of DHL seen at our institution during a 5-year period. In addition, we carried out case-control comparisons of DHL with BL and International Prognostic Index (IPI)-matched DLBCL. The 11 men and 9 women had a median age of 63.5 years (range 32 to 91). Six patients had a history of grade 1 to 2 follicular lymphoma; review of the prior biopsy specimens in 2 of 5 cases revealed blastoid morphology. Eighteen patients had Ann Arbor stage 3 or 4 disease and all had elevated serum lactate dehydrogenase (LDH) levels at presentation. Extranodal disease was present in 17/20 (85%), bone marrow involvement in 10/17 (59%) and central nervous system (CNS) disease in 5/11 (45%). Nineteen patients were treated with combination chemotherapy, of whom 18 received rituximab and 14 received CNS-directed therapy. Fourteen patients (70%) died within 8 months of diagnosis. Median overall survival in the DHL group (4.5 mo) was inferior to both BL (P=0.002) and IPI-matched DLBCL (P=0.04) control patients. Twelve DHL cases (60%) were classified as B-cell lymphoma, unclassifiable, with features intermediate between DLBCL and BL, 7 cases (35%) as DLBCL, not otherwise specified, and 1 case as B-LBL. Distinguishing features from BL included expression of Bcl2 (P<0.0001), Mum1/IRF4 (P=0.006), Ki-67 <95% (P<0.0001), and absence of EBV-EBER (P=0.006). DHL commonly contained the t(8;22) rather than the t(8;14) seen in most BL controls (P=0.001), and exhibited a higher number of chromosomal aberrations (P=0.0009). DHL is a high-grade B-cell neoplasm with a poor prognosis, resistance to multiagent chemotherapy, and clinical and pathologic features distinct from other high-grade B-cell neoplasms. Familiarity with the morphologic and immunophenotypic spectrum of DHL is important in directing testing to detect concurrent IGH-BCL2 and MYC rearrangements when a karyotype is unavailable. The aggressive clinical behavior and combination of genetic abnormalities seen in these cases may warrant categorization as a separate entity in future classifications and call for novel therapeutic approaches.

PRL-2 increases Epo and IL-3 responses in hematopoietic cells

Dual specificity protein tyrosine phosphatase PRL-2 is overexpressed in pediatric acute myeloid leukemia (AML) and is located at human chromosome 1p35, a region often rearranged or amplified in malignant lymphoma and B-cell chronic lymphocytic leukemia (B-CLL). Little is known of the significance of PRL-2 expression in hematopoietic malignancies. Herein we demonstrated that ectopic expression of PRL-2 in murine pre-B-cell line Baf3ER and mouse bone marrow cells induced key features associated with malignant progression and metastasis. PRL-2-transfected Baf3ER cells had augmented growth responses to hematopoietic growth factors Epo or IL-3 with shortened cell cycle, reduced requirement (5x) for Epo in cell survival, increased cell migration (3x), reduced cell adhesion (5x), and conversion to an immature cell morphology in association with increased expression (3x) of stem cell marker Bmi-1. When transduced into mouse bone marrow cells, PRL-2 increased Epo-induced colony formation (4x) and gave rise to larger colonies. These observations provide evidences implicating PRL-2 as a pathogenic molecule in hematopoietic malignancies and suggest its potential as a novel therapeutic target.

Diffuse blastoid B-cell lymphoma: a histologically aggressive variant of t(14;18)-negative follicular lymphoma

Among the diffuse lymphomas of B-cell origin, we have encountered one variant displaying blastoid features that morphologically mimic lymphoblastic lymphoma, the blastoid variant of mantle cell lymphoma, and the so-called blastoid transformation of follicular lymphoma. To better characterize this entity, we studied eight cases morphologically, immunohistochemically, and by fluorescence in situ hybridization (FISH) for cytogenetic abnormalities commonly associated with follicular lymphoma and B-cell lymphomas exhibiting high-grade histological features. All eight cases were presented as de novo neoplasms, and displayed an entirely diffuse (five cases) or only minimal follicular (three cases) growth pattern. The neoplastic lymphoid cells were of medium size with round nuclei, fine chromatin, inconspicuous nucleoli, and high mitotic rate; they expressed CD10, BCL6, and BCL2-a phenotype consistent with follicle center cell origin. A proportion of cases expressed MUM1. Their lack of TdT and CYCLIN D1 distinguished them from lymphoblastic lymphoma and the blastoid mantle cell lymphoma, respectively. The neoplastic lymphoid cells consistently expressed CD43 (seven of eight cases) and occasionally other T-cell-associated antigens, including CD5, CD7, CD8, and CD57. Although all cases overexpressed BCL2, t(14;18) was not detected in any of the five cases examined by FISH; instead, extra copies of chromosome 18 were found in four of five cases. Finally, other cytogenetic abnormalities, including structural abnormalities of BCL6 (allelic loss/gain, rearrangement), monosomy 7, del(13)(q14), and MYC allelic loss, were frequently detected. The combination of a B-cell CD10+ BCL6+ BCL2+ phenotype in the presence of structural abnormalities of BCL6 is consistent with a follicular center cell derivation for our cases. The lack of t(14;18) seen in our cases, although rare in most cases of follicular lymphoma, has been nevertheless reported in cases of follicular lymphoma with a predominantly diffuse growth pattern. The molecular pathogenesis, clinical manifestations, and prognostic significance of these lesions remain to be elucidated.

Genome-wide profiling of follicular lymphoma by array comparative genomic hybridization reveals prognostically significant DNA copy number imbalances

The secondary genetic events associated with follicular lymphoma (FL) progression are not well defined. We applied genome-wide BAC array comparative genomic hybridization to 106 diagnostic biopsies of FL to characterize regional genomic imbalances. Using an analytical approach that defined regions of copy number change as intersections between visual annotations and a Hidden Markov model-based algorithm, we identified 71 regional alterations that were recurrent in at least 10% of cases. These ranged in size from approximately 200 kb to 44 Mb, affecting chromosomes 1, 5, 6, 7, 8, 10, 12, 17, 18, 19, and 22. We also demonstrated by cluster analysis that 46.2% of the 106 cases could be sub-grouped based on the presence of +1q, +6p/6q-, +7, or +18. Survival analysis showed that 21 of the 71 regions correlated significantly with inferior overall survival (OS). Of these 21 regions, 16 were independent predictors of OS using a multivariate Cox model that included the international prognostic index (IPI) score. Two of these 16 regions (1p36.22-p36.33 and 6q21-q24.3) were also predictors of transformation risk and independent of IPI. These prognostic features may be useful to identify high-risk patients as candidates for risk-adapted therapies.

Non-Hodgkin lymphoma with t(14;18): clonal evolution patterns and cytogenetic–pathologic–clinical correlations

PURPOSE

The pattern and frequency of secondary chromosome abnormalities in t(14;18)-carrying non-Hodgkin lymphomas (NHL) were evaluated for differences in relation to histologic NHL subtype and patients' outcome.

METHODS

One hundred and forty-nine NHL patients with t(14;18) and complete cytogenetic, morphologic, and clinical information were selected.

RESULTS

One hundred and twelve cases were follicular lymphoma (FL) and 37 were diffuse large B-cell lymphoma (DLBCL). One hundred and forty cases showed secondary aberrations (94%, median = 6.0). The most frequent were losses from chromosome arms 1p and 6q and +7 (26%). Loss from 1q, +7, and +12 were more frequent in DLBCL than in FL. Loss from 1p, Xp, and -16 were more frequent in FL grade 3 than in FL grades 1 and 2. Patients with <6.0 secondary cytogenetic aberrations had better prognosis than did those with a higher number of aberrations. Trisomy 21 was associated with shorter patient survival. FLIPI score, the number of secondary chromosomal aberrations, and +21 were all of independent prognostic value in Cox multivariate analysis. FL grade 1-3a patients that had received chemotherapy, showed a higher frequency of i(6p) and loss from 6q.

CONCLUSION

Secondary chromosomal aberrations showed some correlation with the morphologic subgroups of t(14;18)-NHL. Trisomy 21 and the presence of >6.0 secondary cytogenetic aberrations both correlated with shorter overall survival.

Molecular pathways in follicular lymphoma

Follicular lymphoma (FL) is one of the most common B-cell non-Hodgkin's lymphomas. The initiating genetic event found in approximately 90% of FL is the t(14;18), causing constitutive expression of the antiapoptotic BCL-2 protein. The exact secondary alterations leading to full FL development are still poorly defined. In this review, we address (i) the genetic pathways associated with tumorigenesis and progression of FL, (ii) the role of micro-environmental factors with emphasis on B-cell receptor ligands and (iii) lymphoma models in mice and what they teach us about lymphomagenesis in man.

New chromosome abnormalities and lack of BCL-6 gene rearrangements in Argentinean diffuse large B-cell lymphomas

OBJECTIVES

Diffuse large B-cell lymphoma (DLBCL) is the most common form of non-Hodgkin lymphomas. Cytogenetic studies have revealed a broad spectrum of clonal genetic abnormalities and complex karyotypes. The purpose of this study was to contribute to the understanding of the genomic alterations associated with this group of lymphomas.

METHODS

Cytogenetic, fluorescence in situ hybridization (FISH) and molecular analyses were performed in 30 cases with DLBCL: 20 de novo DLBCL (dn-DLBCL) and 10 DLBCL secondary to follicular lymphoma (S-DLBCL).

RESULTS

A total of 37 different structural chromosomal rearrangements were found: 27% translocations, 54% deletions, and 19% other alterations. Chromosomes 8, 6, 2, and 9 were the most commonly affected. Interestingly, translocation t(3;14)(q27;q32) and/or BCL-6 gene rearrangements were not observed either by cytogenetic studies or by FISH analysis. Fifteen novel cytogenetic alterations were detected, among them translocations t(2;21)(p11;q22) and t(8;18)(q24;p11.3) appeared as sole structural abnormalities. Translocation t(14;18)(q32;q21) and/or BCL-2-IGH gene rearrangements were the genomic alterations most frequently observed: 50% of S-DLBCL and 30% of dn-DLBCL. Deletions del(4)(q21), del(6)(q27), del(8)(q11), and del(9)(q11) were recurrent. The most common gains involved chromosome regions at 12q13-q24, 7q10-q32, and 17q22-qter; 6q was the most frequently deleted region, followed by losses at 2q35-qter, 7q32-qter, and 9q13-qter. Four novel regions of loss were identified: 5q13-q21, 2q35-qter (both recurrent in our series), 4p11-p12, and 17q11-q12.

CONCLUSIONS

These studies emphasize the value of combining conventional cytogenetics with FISH and molecular studies to allow a more accurate definition of the genomic aberrations involved in DLBCL.

Cytogenetics of lymphomas

Cytogenetic analysis is now a routine part of the diagnosis and management of a significant number of lymphoid malignancies. Whilst conventional cytogenetics remains the most comprehensive method for assessing chromosome abnormalities, the technical difficulties associated with conventional cytogenetics in most lymphomas has resulted in increased use of fluorescence in situ hybridisation (FISH) to identify specific abnormalities that are useful in either the diagnosis or management of these disorders. The finding of one of the Burkitt's translocations is of major importance in the diagnosis of Burkitt's and Burkitt's-like lymphomas, whereas the t(14;18), although seen in most follicular lymphomas (FL), is not usually required to make a diagnosis. Thus, whilst cytogenetics may be of interest in FL, it is not an essential part of the diagnostic work-up. Conventional cytogenetics may be useful for identifying markers of resistance to Helicobacter pylori therapy in MALT lymphomas. In disorders such as Hodgkin lymphoma, hairy cell leukaemia and lymphoplasmacytoid lymphoma, although many cytogenetic abnormalities have been observed, no consistent or specific abnormalities have been identified and so, at this point in our knowledge of the genetics of these disorders, cytogenetics cannot be considered a useful test for either diagnosis or prognosis. In contrast, the diagnosis of mantle cell lymphoma is now dependent upon the identification of the 11;14 translocation that results in cyclin D1 up-regulation. It is widely acknowledged that FISH is the most consistently useful test to identify the juxtaposition of the CCND1 and IGH genes in mantle cell lymphoma and is regarded as the 'gold standard'. FISH also has a role in identifying genetic abnormalities of prognostic significance in chronic lymphocytic leukaemia. Given the wealth of genetic and cytogenetic abnormalities that are continuing to be found in chronic lymphoid malignancies, it will be some time before the optimal use of both conventional cytogenetics and FISH is established in the diagnosis and management of lymphomas.

Secondary chromosomal abnormalities predict outcome in pediatric and adult high-stage Burkitt lymphoma

BACKGROUND

Karyotypic abnormalities in sporadic Burkitt lymphoma (BL) have been described extensively. However, to the authors' knowledge, very limited studies have focused on the secondary chromosomal abnormalities in pediatric BL as compared with those of adult BL and on their prognostic impact.

METHODS

A retrospective analysis was performed in all pediatric and adult patients at 2 institutions, with a morphologic diagnosis of BL, pretherapy tumor karyotype available, and t(8;14), t(8;22), or t(2;8) present.

RESULTS

There were 33 children and 37 adults. The majority of the patients (95%) had Stage III/IV disease. There were no statistically significant differences noted in karyotype complexity and the nature of the chromosomal abnormalities between these 2 groups. Abnormalities of chromosomes 13 (13q) and 22 (22q) had a negative impact on prognosis in children. In adults, abnormalities of chromosome 17 appeared to have a negative impact.

CONCLUSIONS

The current findings suggest that karyotypic information can be used for refining risk stratification in patients with BL.

Expression of human 8-oxoguanine DNA glycosylase (hOGG1) in follicular lymphoma

The human homologue of the yeast DNA repair enzyme 8-oxoguanine DNA glycosylase (hOGG1) repairs oxidatively damaged guanosine nucleotides in DNA. This enzyme is highly expressed in reactive germinal centers, where lymphoid cells are under oxidative stress, and has been thought to protect lymphocytes from mutation. As a first step to investigate the role of hOGG1 in lymphomagenesis, we evaluated hOGG1 expression in follicular lymphoma. Immunohistochemistry was performed on formalin-fixed paraffin-embedded tissue of 28 follicular lymphoma cases (16 grade 1, seven grade 2, and five grade 3) to evaluate the expression of hOGG1 in neoplastic follicles. Reactive germinal centers of non-neoplastic tonsil and lymph node tissue were also examined. Fluorescent-in-situ hybridization (FISH) was performed using a DNA probe from BAC clone RP11-266J6 corresponding to 3p25, where the hOGG1 gene resides, to evaluate for the presence or absence of a deletion. In reactive germinal centers, the majority of centroblasts and centrocytes were positive for hOGG1. In contrast, the majority (21 of 28 or 75%) of follicular lymphoma cases showed absent/minimal expression of hOGG1. Only four of 28 (14%) follicular lymphoma cases revealed the same levels of hOGG1 expression as reactive germinal centers. There was no correlation between hOGG1 expression and histologic grade. None of the 16 cases evaluated by FISH showed a deletion of hOGG1. Furthermore, absent/minimal hOGG1 expression was observed in four of six Bcl-2-negative follicular lymphoma cases. Our findings suggest that absent/minimal hOGG1 expression occurs in the majority of follicular lymphomas. The downregulation of hOGG1 does not appear to be due to a deletion of the hOGG1 locus. Additionally, finding absent/minimal hOGG1 expression in a subset of Bcl-2-negative follicular lymphomas suggests that hOGG1 may have utility in diagnosing Bcl-2-negative follicular lymphomas.

Chromosomal aberrations in follicular non-Hodgkin lymphomas of Japanese patients, detected with comparative genomic hybridization and polymerase chain reaction analysis

The t(14;18)(q32.3;q21), hallmark of follicular lymphoma (FL), is less frequently observed in Asian patients than in Westerners. Little is known about additional chromosomal aberrations in Asian FL patients. We applied comparative genomic hybridization (CGH) to screen for genomic imbalances in 32 biopsy samples from 23 Japanese patients with nodal FL. The t(14;18) was assessed with polymerase chain reaction (PCR) using primers for the major (MBR), 3'MBR, minor (mcr), 5'mcr, and intermediate breakpoint cluster regions (icr). In 17 of 23 patients, CGH analyses detected genomic imbalances. Gains frequently affected chromosomes 18p (6 of 23), X (5 of 23), 5 (4 of 23), 12 (4 of 23), 2 (3 of 23), and 16 (3 of 23). The only recurrent loss affected chromosome 6q (2 of 23). A t(14;18) was detected in 13 of 23 patients (56.5%). Breakpoints were located in the MBR (10 patients), in the 3'MBR, in the mcr, and in the icr (1 patient each). The frequency of aberrations detected by CGH as well as relapse-free survival were not distinctly different between patients with and without a t(14;18). In summary, no significant difference in the overall frequency of aberrations compared with Westerners was found. Despite the extended primer set used, the frequency of PCR-detected t(14;18) remained low. Additional studies are required to assess the reasons for geographic variation in FL.

Cytologic diagnosis of Burkitt lymphoma

BACKGROUND

The diagnosis and classification of lymphoma require correlation of morphologic, immunophenotypic, and molecular-cytogenetic studies. Fine-needle aspiration biopsy (FNAB) is a valuable diagnostic technique that allows material to be collected for these ancillary studies, and for morphologic evaluation.

METHODS

The authors report a series of seven cases clinically or morphologically suspicious for Burkitt lymphoma. Fluorescence in situ hybridization studies (FISH) for c-myc were performed on FNAB material and correlated with cytologic and immunophenotypic data.

RESULTS

Six of seven specimens were positive for c-myc rearrangement by FISH. However, only three of these cases represented Burkitt lymphoma, with one additional case of atypical Burkitt lymphoma. The other cases included diffuse large B-cell lymphoma, monomorphic posttransplant B-cell lymphoma, and an aggressive B-cell lymphoma, with the latter case negative for c-myc rearrangement by FISH. Of 2 non-Burkitt lymphoma specimens tested, 1 was positive for the immunoglobulin H/bcl-2 rearrangement, in addition to the c-myc rearrangement, suggesting transformation from a lower grade lymphoma.

CONCLUSIONS

These cases illustrated the value of FNAB in the diagnosis of Burkitt lymphoma, as well as the importance of obtaining material for, and integrating results of, ancillary studies for the final diagnosis.

Low-grade follicular lymphoma with t(14;18) presents a homogeneous disease entity otherwise the rest comprises minor groups of heterogeneous disease entities with Bcl2 amplification, Bcl6 translocation or other gene aberrances

Follicular lymphomas (FL) are morphologically classified into grades 1, 2, 3a and 3b by the World Health Organization. Bcl2, Bcl6 and CD10 are phenotypic markers of FL while the Bcl2 t(14;18) and Bcl6 t(3q27) gene translocations are common genetic changes. However, to date, there has been no integrated analysis based on phenotype, grade and genotype from large numbers of FL cases. We graded 261 cases of FL and determined their phenotypes and gene alterations. According to the antigen markers and gene alterations of 147 cases, we classified FL into typical and the others types. The typical group, which includes 69% cases of FL, is characterized by low histological grade (grade 1, 2), coexpression of BCL2 and CD10 and Bcl2 gene translocation. The rest comprises a small part of low-grade FL without Bcl2 gene translocation and high-grade (grade 3a, 3b) FL. These FLs include some heterogeneous disease entities. They are characterized by high histological grade (87%), no definite expression of BCL2 or CD10 and several kinds of gene aberrances including Bcl2 translocation, Bcl6 translocation, Bcl2 amplification or other unknown gene abnormality. Our findings indicate that typical FL presents a homogeneous disease entity whereas the rest comprises heterogeneous diseases entities.

Variant t(14;18) in malignant lymphoma: a report of seven cases

The BCL2 gene was identified through molecular analysis of the breakpoints involved in the t(14;18)(q32;q21) found in the majority of follicular lymphomas (FL). Variant translocations leading to juxtaposing of the BCL2 with either the IGK or IGL gene have been recognized in B-cell malignant lymphoma, although they are rare. We identified seven lymphoma cases that had variant translocations. Three cases had simple translocations involving two chromosomal regions: t(18;22)(q21;q11.2) in two cases and t(2;18)(p11.2;q21) in the third case. Complex translocations affecting more than two chromosomes were seen in the remaining four cases. Fluorescence in situ hybridization using the LSI IGH/BCL2 DNA probes revealed rearrangements of the BCL2 gene locus in all cases. In addition, expression of BCL2 protein was seen in all cases; only five of the seven cases expressed BCL6 protein. Morphologically, the lymphomas were categorized as B-cell follicular lymphoma in six cases and in the seventh case as diffuse large cell lymphoma (Richter syndrome) transformed from preexisting chronic lymphocytic leukemia (CLL). In case 2, the variant t(18;22) was seen as a secondary aberration evolving from a trisomy 12 clone. The findings revealed that BCL2 rearrangements in some malignant lymphomas occur through variant simple or complex chromosomal translocations, but always involving the IGH, IGK, or IGL chromosomal site. In addition, fluorescence in situ hybridization proved to be an important tool in evaluating these cases by showing IGH/BCL2 gene fusion or repositioning of the BCL2 gene.

An additional segment at 1p36 derived from der(18)t(14;18) in patients with diffuse large B-cell lymphomas transformed from follicular lymphoma

The particular translocation in follicular lymphomas (FLs) is a t(14;18)(q32;q21), recombining the immunoglobulin heavy chain (IgH) gene on chromosome 14 with the B-cell leukemia/lymphoma 2 (BCL2) gene on chromosome 18. Some low-grade FLs are aggressively transformed into diffuse large B-cell lymphomas, presumably by acquisition of secondary chromosomal changes, including chromosomal band 1p36. A common example is add(1)(p36). Because it is difficult to identify the origin of add(1)(p36) even on high-resolution G-banding analysis, we used spectral karyotyping (SKY) and double-color fluorescence in situ hybridization (DC-FISH) to define the t(14;18) and the extra band at 1p36 in two cases of diffuse large B-cell lymphoma (DLBCL). SKY revealed that the extra chromosomal segment on 1p36 was derived from chromosome 18. DC-FISH defined BCL2/IgH fusion signals at 1p36 in addition to t(14;18), suggesting that BCL2/IgH fusion at 1p36 was an evolutionary alteration following the primary BCL2/IgH translocation on der(18) in both cases. Our results indicate that IgH alleles, implicated in chromosomal rearrangement, may themselves frequently be targets for secondary translocations, suggesting that multiple IgH translocations and insertions are associated with the progression of FL.

The pattern and frequency of t(14;18) translocation and immunophenotype in Asian follicular lymphoma

AIMS

Follicular lymphoma is frequently associated with t(14;18)(q32;q21) translocation. This study was undertaken to determine the pattern of Bcl-2, CD10 and Bcl-6 expression in relation to t(14;18) translocation in follicular lymphoma from a cohort of a multi-ethnic Asian population.

METHODS AND RESULTS

Sixty-two cases of follicular lymphoma were retrieved for immunohistochemistry, and t(14;18) translocation analysis by polymerase chain reaction and fluorescent in-situ hybridization techniques. Bcl-2 expression was present in 74% of the cases. CD10 expression was also relatively low (61%), with decreasing frequency of expression in high-grade tumours. Bcl-6 protein was expressed in most of the tumours (88%) regardless of the tumour grade. The t(14;18) translocation was detected in 46 cases (74%) with an extremely high rate of t(14;18) translocation in ethnic Indian cases (100%).

CONCLUSION

The frequency of t(14;18) translocation in this series of follicular lymphomas was higher when compared with previous Asian reports, but in accordance with European and North American findings. CD10 expression is strongly associated with a t(14;18) translocation event, but the overall CD10 expression was relatively low, possibly due to the high proportion of high-grade tumours in the series. t(14;18) translocation was not associated with Bcl-2 or Bcl-6 expression.

Expression of Bcl-2 family members and presence of Epstein-Barr virus in the regulation of cell growth and death in classical Hodgkin's lymphoma

AIMS

To examine the expression of the Bcl-2 family of proteins (Bcl-2, Bcl-x, Bcl-xL and Bax) in classical Hodgkin's lymphoma (cHL) and to correlate the expression of these proteins with proliferation, apoptosis and the presence of Epstein-Barr virus (EBV).

METHODS AND RESULTS

Expression of the Bcl-2 family of proteins was detected by immunohistochemistry, proliferation was determined by Ki67 labelling and apoptosis by TUNEL in-situ hybridization. EBV was detected by Epstein-Barr virus early RNA (EBER) in-situ hybridization. Expression of Bcl-2, Bcl-x, Bcl-xL and Bax was detected in the Hodgkin/Reed-Sternberg (H/RS) cells in 43.7% (27/62), 87.5% (56/64), 67.2% (41/61) and 74.6% (47/63) of the cHL cases, respectively. EBER was detected in 53% (35/66) of the cases, whereas Ki67 was observed in 86.7% (52/60) of the cases. Apoptotic H/RS cells were observed infrequently, and only 43.2% (11/26) of the cases showed an apoptotic index of > or = 10% in the H/RS cells. A statistically significant inverse relationship was observed between the expression of Bcl-2 and the presence of EBV (P = 0.003). Bcl-xL showed an inverse correlation with apoptosis in the H/RS cells (P = 0.004).

CONCLUSIONS

The higher Bcl-xL expression (67.2%) compared with Bcl-2 expression (43.5%) observed in cHL as well as the statistically significant inverse relationship between Bcl-xL and apoptosis suggests that Bcl-xL plays an important role in the survival of H/RS cells. Expression of Bax may be neutralized by other anti-apoptotic members of the family such as Bcl-2 and/or Bcl-xL.

Translocation (16;18)(p13;q21.3) in follicular lymphoma

We describe a novel t(16;18)(p13;q21.3) in a male patient with follicular lymphoma. This unique chromosomal rearrangement has never been described in patients with follicular lymphoma. The breakpoint of 16p13 has several hematopoietic neoplasm-related genes such as MHC2TA, a master regulatory gene for HLA-D, and BCMA, tumor necrosis factor receptor super-family. The majority of follicular lymphomas have a rearrangement of the BCL2 gene, which is a pathogenetic factor in their development. The diagnostic and prognostic significance of this new translocation is yet to be determined.

Improvement in the detection rate of t(14;18) translocation on paraffin-embedded tissue: a combination approach using PCR and FISH

AIMS

PCR has been the primary method used for the detection of t(14;18) translocation in formalin-fixed, paraffin-embedded tissues. This technique mainly targets the well-characterised breakpoint regions in chromosomes 14 and 18. FISH is now applicable on paraffin tissue sections and has been suggested to be capable of detecting essentially 100% of t(14;18) translocated cases. In this study, we described the application of both PCR and FISH for the detection of t(14;18) translocation.

METHODS

Fifty follicular lymphoma cases were retrieved from the files of the Department of Pathology, University of Malaya Medical Centre (UMMC). Nested PCR amplification of MBR/JH and mcr/JH was performed in these cases, and those cases that did not demonstrate the translocation were subjected to FISH analysis.

RESULTS

Thirty cases (60%) had t(14;18) translocation detected by PCR, 25 (50%) had breakpoint with MBR and five (10%) involved mcr. Twenty cases without detectable t(14;18) translocation by PCR were analysed by FISH. Eleven cases were successfully probed, and four of them showed positive translocation signal.

CONCLUSIONS

The combination of PCR and FISH analysis on paraffin tissue sections for the detection of t(14;18) translocation increases the sensitivity of detection from 60 to 68%. Problems encountered in our FISH analysis on tissue sections impose certain limitations in using this technique for retrospective screening of large number of samples. Therefore, we suggested the application of PCR as the first screening tool on retrospective archival materials, followed by FISH on those PCR-negative cases.

A novel t(2;6)(p12;q23) appearing during transformation of follicular lymphoma with t(18;22)(q21;q11) to diffuse large cell lymphoma

Follicular lymphoma is characterized genetically by t(14;18)(q32;q21), whereas t(18;22)(q21;q11), a rare variant form of t(14;18), has been preferentially observed in chronic lymphocytic leukemia (CLL). We describe here an unusual case of follicular lymphoma with a t(18;22)(q21;q11), that progressed to diffuse large cell lymphoma with a novel t(2;6)(p12;q23). Spectral karyotyping revealed that add(2)(p12) and add(6)(q23) were derived from a t(2;6)(p12;q23). Fluorescence in situ hybridization analysis confirmed rearrangements of the BCL2 gene at 18q21 and the BCL6 gene at 3q27. Our results indicate that a reciprocal translocation involving 6q23 could be implicated in the progression of follicular lymphoma and that t(18;22) may have a specific role in the pathogenesis of follicular lymphoma as well as CLL.

Abnormalities on 1q and 7q are associated with poor outcome in sporadic Burkitt's lymphoma. A cytogenetic and comparative genomic hybridization study

Comparative genomic hybridization (CGH) studies have demonstrated a high incidence of chromosomal imbalances in non-Hodgkin's lymphoma. However, the information on the genomic imbalances in Burkitt's Lymphoma (BL) is scanty. Conventional cytogenetics was performed in 34 cases, and long-distance PCR for t(8;14) was performed in 18 cases. A total of 170 changes were present with a median of four changes per case (range 1-22). Gains of chromosomal material (143) were more frequent than amplifications (5) or losses (22). The most frequent aberrations were gains on chromosomes 12q (26%), Xq (22%), 22q (20%), 20q (17%) and 9q (15%). Losses predominantly involved chromosomes 13q (17%) and 4q (9%). High-level amplifications were present in the regions 1q23-31 (three cases), 6p12-p25 and 8p22-p23. Upon comparing BL vs Burkitt's cell leukemia (BCL), the latter had more changes (mean 4.3 +/- 2.2) than BL (mean 2.7 +/- 3.2). In addition, BCL cases showed more frequently gains on 8q, 9q, 14q, 20q, and 20q, 9q, 8q and 14q, as well as losses on 13q and 4q. Concerning outcome, the presence of abnormalities on 1q (ascertained either by cytogenetics or by CGH), and imbalances on 7q (P=0.01) were associated with a short survival.

Identification of chromosomal copy number changes associated with transformation of follicular lymphoma to diffuse large B-cell lymphoma

The histological transformation from a follicular lymphoma (FL) to a diffuse large B-cell lymphoma (DLBL) occurs in 22% to 30% of all cases of FL. The aim of this study was to identify specific chromosomal gains/losses associated with transformation of FL to DLBL, in addition to the well-known mechanisms like p53 mutation and protein expression and c-myc translocation and up-regulation. This is the first study to meet 2 important conditions for such a comparison. First, we demonstrate that the FL and the DLBL were clonally related, based on identical immunoglobulin gene rearrangements in 5 of the 6 cases. Second, we used laser microdissection microscopy to isolate only the neoplastic cells from the initial FL samples. The results indicate that no single chromosomal abnormality seems to be responsible for the transformation of FL to DLBL. P53 protein overexpression was found in 4 and c-myc translocation in 3 of the 6 transformed DLBLs, but not in the initial FL samples. Additional chromosomal abnormalities were detected by comparative genomic hybridization in all 6 cases when the DLBL was compared with the FL. In the 5 cases with transformation of grade 1 or 2 FL to DLBL, gains at chromosomes 7 (5 of 5 cases), 10p1 (3 of 5 cases), 12 (3 of 5 cases), and 20p13 (2 of 5 cases) and loss at 9q (4 of 5 cases) were the most frequently found abnormalities. A gain on chromosome 7p, in combination with a loss on 9q, was found in 4 of the 5 DLBL that transformed from FL grade 1 or 2.

Multicolour fluorescence in situ hybridization analysis of t(14;18)-positive follicular lymphoma and correlation with gene expression data and clinical outcome

In order fully to identify secondary chromosomal alterations, such as duplications, additions and marker chromosomes that remained unresolved by G banding, 60 cases of t(14;18)-positive follicular lymphoma (FL) were analysed by multicolour karyotyping techniques [multicolour fluorescence in situ hybridization (MFISH)/multicolour banding for chromosome 1 (MBAND1)]. A total of 165 additional structural chromosomal aberrations were delineated. An increased frequency of chromosomal gains involving X, 1q, 2, 3q27-q29, 5, 6p11-p21, 7, 8, 11, 12, 14q32, 17q, 18 and 21 and deletions of 1p36, 3q28-q29, 6q, 10q22-q24 and 17p11-p13 was revealed by the MFISH/MBAND1 analysis. Balanced translocations other than t(14;18) were uncommon, whereas unbalanced translocations were numerous. Deletion of 1p36 and duplication of 1p33-p35, 1p12-p21 and 1q21-q41 were regularly involved in chromosome 1 alterations, seen in 53% of the cases. A strong correlation was demonstrated between gains of individual chromosomal bands and increased gene expression, including 1q22/MNDA, 6p21/CDKN1A, 12q13-q14/SAS, 17q23/ZNF161, 18q21/BCL2 and Xq13/IL2RG. Unfavourable overall survival was associated with del(1)(p36) and dup(18q). These data support the notion that translocation events are primarily responsible for FL disease initiation, whereas the unbalanced chromosomal gains and losses that mirror the gene expression patterns characterize clonal evolution and disease progression, and thus provide further insights into the biology of FL.

Burkitt lymphoma arising in organ transplant recipients: a clinicopathologic study of five cases

We report five cases of Burkitt lymphoma arising in organ transplant recipients. There were four men and one woman with a mean age of 35 years. All were solid organ recipients with three renal, one liver, and one double lung transplantation. The time interval between organ transplantation and lymphoma averaged 4.5 years. Patients typically presented with high-stage disease with generalized lymphadenopathy and bone marrow involvement. Histology showed classic Burkitt lymphoma or atypical variant/Burkitt-like morphology. C-MYC rearrangement, including three cases with immunoglobulin heavy chain and two cases with lambda light chain, and Epstein-Barr virus were detected in all the cases. Additional chromosomal abnormalities were present in two of three cases and p53 mutation was found in one of three cases. Aberrant genotype and phenotype were frequently encountered, including minor monoclonal or oligoclonal T-cell populations and undetectable surface immunoglobulin light chain expression. Four patients received antilymphoma regimens, with combination chemotherapy (three patients) and/or Rituximab (three patients), in addition to reduction of immunosuppression. All four patients achieved complete remission. We conclude that posttransplant Burkitt lymphoma represents a characteristic clinicopathologic entity and occurs later after transplantation. Genotypic and phenotypic aberrations are often present. Rituximab may be an effective alternative to conventional combination chemotherapy in the treatment of a posttransplant Burkitt lymphoma.

The classification of lymphomas: a new beginning or the end of an era?

The World Health Organisation Classification of Tumours of the Haematopoietic and Lymphoid Tissues has recently been published. This is the latest in a long line of classifications of haematological malignancies and will be the international standard. It is now possible to achieve high levels of diagnostic accuracy for the main types of lymphoma. However, many of the entities encompass a wide spectrum of clinical outcomes and this approach to classification may be insufficiently precise for the future needs of haematological oncology. Rapid progress in targeted therapies may require further developments in tumour classification based on pathogenic features rather than arbitrary morphological criteria.