BCL2 protein expression in follicular lymphomas with t(14;18) chromosomal translocations

Current and future therapies for follicular lymphoma

Follicular lymphoma (FL) is an indolent, germinal center B cell-derived lymphoid neoplasm, for which recent advances in treatment have substantially improved patient survival. However, FL remains an incurable and heterogeneous disease, with groups of patients experiencing early disease progression, histologic transformation, or a high risk of treatment-related toxicity. Additionally, FL is a continually relapsing disease, and response rates and disease-control intervals decrease with each subsequent line of therapy. In this review, we explore the current treatment landscape for relapsed or refractory FL and promising therapies in development, highlighting the efficacy and potential risks of each treatment. We provide a real-world perspective on the unmet needs of patients with FL. Novel therapeutic approaches in development offer a wide array of options for clinicians when treating relapsed or refractory FL. A nuanced approach is required to address the needs of individual patients, taking into consideration both the risks and benefits of each treatment option, as well as patient preferences.

Clinicopathological and prognostic significance of BCL2, BCL6, MYC, and IRF4 copy number gains and translocations in follicular lymphoma: a study by FISH analysis

BCL2 translocation is the genetic hallmark of follicular lymphoma (FL). Besides BCL2 translocation, copy number (CN) gains and translocations of BCL6, MYC, and IRF4 have also been detected in FL, but there is little information regarding their prognostic significance. This retrospective study used fluorescence in situ hybridization (FISH) to analyze BCL2, BCL6, MYC, and IRF4 translocations and CN gains in 105 FL cases. Genetic translocations were detected for BCL2 (n = 64; 72.7%), BCL6 (n = 14; 15.9%), and MYC (n = 2; 2.3%); no case showed IRF4 translocation. Overall, 23 (26.1%), 30 (34.1%), 12 (13.8%), and 10 (11.0%) cases showed CN gains in BCL2, BCL6, MYC, and IRF4, respectively. BCL6 CN gain was a prognostic factor for worse overall survival, demonstrating a trend toward significance in multivariate analysis (HR =8.769, p = 0.056). BCL6 CN gain in FL might be associated with aggressive biologic behavior.

Molecular and clinical progress in follicular lymphoma lacking the t(14;18) translocation (Review)

Although the majority of patients with follicular lymphoma (FL) harbor the t(14;18)(q32;q21) IGH/BCL2 gene rearrangement that leads to the overexpression of BCL2 protein, approximately 20% of FL cases lack t(14;18)(q32;q21). It is considered that BCL2 overexpression underscores the development of the majority of cases of FL and their transformation to more aggressive lymphoma [known as transformed FL (tFL)]. However, FL cases lacking the t(14;18)(q32;q21) translocation exhibit symptoms analogous to their t(14;18)‑positive counterparts. An important goal of recent research on FL has been to clarify the distinctions between the two different forms of FL. Numerous studies have shed light onto the genetic and molecular features of t(14;18)‑negative FL and the related clinical manifestations. In this review, we summarize the current knowledge of t(14;18)‑negative FL occurring in the lymph nodes with an emphasis on the underlying molecular and clinical features. In addition, novel treatment directions are discussed.

Lack of Bcl-2 expression in feline follicular lymphomas

Bcl-2, an anti-apoptotic protein, is commonly overexpressed in follicular lymphomas in humans. This is usually the result of a chromosomal translocation that transposes the Bcl-2 gene into the immunoglobulin gene locus. The immunohistochemical assessment of this overexpression can be used as a tool for the differentiation of follicular lymphoma and follicular hyperplasia. In cats, little information about the expression of Bcl-2 in follicular lymphoma exists. We investigated 18 follicular lymphomas histologically and immunohistochemically for the expression of Bcl-2, CD3, CD45R, and feline leukemia virus. Clonality was assessed by PCR for antigen receptor gene rearrangements. Although the histology resembled that of their human counterparts, diffuse expression of Bcl-2 within the follicles of the feline lymphomas, as seen in human cases, was not present. Only single cells within the follicles, comparable to the reactive controls, were positive for Bcl-2 expression. The mean survival time of 4.6 y confirmed the indolent character of the tumor. None of the clinical parameters assessed were statistically significant predictors of survival. Furthermore, a statistically significant difference in survival of animals with or without anti-neoplastic therapy was also not demonstrable.

Follicular Lymphoma Diagnostic Caveats and Updates

CONTEXT.—

Follicular lymphoma is a common small B-cell lymphoma, likely to be encountered by any practicing pathologist, regardless of specialty. Although the features of typical follicular lymphoma are well known and in most instances easily identifiable, there are lesser-appreciated morphologic appearances that can raise alternative diagnostic possibilities. The limited tissue available in core needle biopsies can make it additionally challenging to thoroughly evaluate those features in the context of architecture. Furthermore, ancillary testing including immunohistochemistry and molecular/genetic analysis do not always show classic findings and may pose additional challenges to interpretation.

OBJECTIVES.—

To review the morphologic features of follicular lymphoma with a discussion of morphologic variants and mimics; to discuss pitfalls of ancillary testing and provide the practicing pathologist with an appropriate context for interpretation of immunohistochemical and molecular/genetic studies when follicular lymphoma is part of the differential diagnosis; and to propose diagnostic strategies when there is limited tissue for evaluation.

DATA SOURCES.—

We used examples of follicular lymphoma from our institution as well as a review of the literature, with a focus on the diagnostic aspects that are broadly relevant to a general pathology practice.

CONCLUSIONS.—

Follicular lymphoma can occasionally present with atypical morphologic, immunohistochemical, or molecular/genetic features. In particular, those findings can be difficult to interpret in the setting of a limited tissue sample. Awareness of those possibilities will help guide the pathologist to a more accurate and precise diagnosis.

Novel gene fusion of PRCC-MITF defines a new member of MiT family translocation renal cell carcinoma: clinicopathological analysis and detection of the gene fusion by RNA sequencing and FISH

AIMS

MITF, TFE3, TFEB and TFEC belong to the same microphthalmia-associated transcription factor family (MiT). Two transcription factors in this family have been identified in two unusual types of renal cell carcinoma (RCC): Xp11 translocation RCC harbouring TFE3 gene fusions and t(6;11) RCC harbouring a MALAT1-TFEB gene fusion. The 2016 World Health Organisation classification of renal neoplasia grouped these two neoplasms together under the category of MiT family translocation RCC. RCCs associated with the other two MiT family members, MITF and TFEC, have rarely been reported. Herein, we identify a case of MITF translocation RCC with the novel PRCC-MITF gene fusion by RNA sequencing.

METHODS AND RESULTS

Histological examination of the present tumour showed typical features of MiT family translocation RCCs, overlapping with Xp11 translocation RCC and t(6;11) RCC. However, this tumour showed negative results in TFE3 and TFEB immunochemistry and split fluorescence in-situ hybridisation (FISH) assays. The other MiT family members, MITF and TFEC, were tested further immunochemically and also showed negative results. RNA sequencing and reverse transcription-polymerase chain reaction confirmed the presence of a PRCC-MITF gene fusion: a fusion of PRCC exon 5 to MITF exon 4. We then developed FISH assays covering MITF break-apart probes and PRCC-MITF fusion probes to detect the MITF gene rearrangement.

CONCLUSIONS

This study both proves the recurring existence of MITF translocation RCC and expands the genotype spectrum of MiT family translocation RCCs.

Protocadherin γ A3 is expressed in follicular lymphoma irrespective of BCL2 status and is associated with tumor cell growth

Protocadherin genes (PCDHs) have been suggested to act as tumor suppressor genes in various tumor types. Previous studies have demonstrated the upregulation of certain PCDH-γ subfamily genes in nodal and duodenal follicular lymphoma (FL) using gene expression analyses. However, the mechanisms and associated molecular function of PCDH-γ subfamily gene upregulation in FL remain to be elucidated. The present study examined the expression of PCDHGA3, an upregulated PCDH-γ gene subfamily member, in B-cell lymphoma 2 (BCL2)-positive and -negative FL, and evaluated its association with tumor cell proliferation in an FL-derived cell line. Immunohistochemical analysis demonstrated that the majority of FL grade 1–2 samples (19/20; 95%) and over half of grade 3A FL samples (5/9; 56%) were PCDHGA3-positive, whereas only 1/17 reactive lymphoid hyperplasia samples was positive. Notably, this positivity was widely observed in samples of BCL2-negative FL (13/15; 87%) and FL with diffuse area (10/10; 100%). The FL-derived cell line FL18 exhibited strong PCDHGA3 expression, similar to the patient samples, and its proliferation was suppressed by PCDHGA3 gene knockdown. Genes expressed concomitantly with PCDHGA3 were selected from gene expression data, and TNFRSF6B, a member of the tumor necrosis factor receptor superfamily, was among the top five most strongly correlated genes. Coexpression of TNFRSF6B and PCDHGA3 was observed immunohistochemically in FL18 cells, suggesting potential cooperation in tumor cell maintenance. In conclusion, the results of the present study indicated that PCDHGA3 was expressed in FL irrespective of BCL2 status and grading and was associated with cell proliferation. Further studies involving molecular genetic analyses are required to elucidate the mechanisms underlying the activity of PCDHGA3 in FL.

Molecular Pathology: Predictive, Prognostic, and Diagnostic Markers in Lymphoid Neoplasms

Lymphoid neoplasms show great diversity in morphology, immunophenotypic profile, and postulated cells of origin, which also reflects the variety of genetic alterations within this group of tumors. This review discusses many of the currently known genetic alterations in selected mature B-cell and T-cell lymphoid neoplasms, and their significance as diagnostic, prognostic, and therapeutic markers. Given the rapidly increasing number of genetic alterations that have been described in this group of tumors, and that the clinical significance of many is still being studied, this is not an entirely exhaustive review of all of the genetic alterations that have been reported.

Genetic aberrations in small B-cell lymphomas and leukemias: molecular pathology, clinical relevance and therapeutic targets

Small B-cell lymphomas and leukemias (SBCLs) are a clinically, morphologically, immunophenotypically and genetically heterogeneous group of clonal lymphoid neoplasms, including entities such as chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL), mantle cell lymphoma (MCL), follicular lymphoma (FL), lymphoplasmacytic lymphoma (LPL), marginal zone lymphoma (MZL) and hairy cell leukemia (HCL). The pathogenesis of some of these lymphoid malignancies is characterized by distinct translocations, for example t(11;14) in the majority of cases of MCL and t(14;18) in most cases of FL, whereas other entities are associated with a variety of recurrent but nonspecific numeric chromosomal abnormalities, as exemplified by del(13q14), del(11q22), and +12 in CLL, and yet others such as LPL and HCL that lack recurrent or specific cytogenetic aberrations. The recent surge in next generation sequencing (NGS) technology has shed more light on the genetic landscape of SBCLs through characterization of numerous driver mutations including SF3B1 and NOTCH1 in CLL, ATM and CCND1 in MCL, KMT2D and EPHA7 in FL, MYD88 (L265P) in LPL, KLF2 and NOTCH2 in splenic MZL (SMZL) and BRAF (V600E) in HCL. The identification of distinct genetic lesions not only provides greater insight into the molecular pathogenesis of these disorders but also identifies potential valuable biomarkers for prognostic stratification, as well as specific targets for directed therapy. This review discusses the well-established and recently identified molecular lesions underlying the pathogenesis of SBCLs, highlights their clinical relevance and summarizes novel targeted therapies.

Rare double-hit with two translocations involving IGH both, with BCL2 and BCL3, in a monoclonal B-cell lymphoma/leukemia

Background

Chronic Lymphocytic Leukemia (CLL) is a lymphoproliferative disease characterized by multiple recurring clonal cytogenetic anomalies and is the most common leukemia in adults. Chromosomal abnormalities associated with CLL include trisomy 12 and IGH;BCL3 rearrangement [t(14;19)(q32;q13)] that juxtaposes a proto-oncogenic gene BCL3 and an immunoglobulin heavy chain, a translocation that may be associated with shorter survival. In addition to the IGH;BCL3 rearrangement, other translocations involving 14q32 locus are involved in various lymphoproliferative pathologies pointing toward the significance of IGH locus in oncogenic progression. Significantly, in the majority of B-cell neoplasms that carry an IGH;BCL3 rearrangement, it is a sole translocation involving an IGH locus.

Case Presentation

We report a patient who, in addition to trisomy 12, carried a rare double-hit translocation characterized by the IGH;BCL3 translocation and an additional clonal IGH;BCL2 translocation involving IGH and another proto-oncogene BCL2, t(14;18)(q32;q21), commonly found in follicular lymphoma. Further single nucleotide polymorphism (SNP) array-based analysis detected a duplication of the 58.8 kb region at 19q13.32 adjacent to the BCL3 translocation junction on chromosome 19q13. Interestingly, the duplicated region contained ERCC2 gene, which encodes a DNA excision repair protein involved in the cancer-prone syndrome, xeroderma pigmentosum.

Conclusions

Taken together our findings indicate the existence of double-translocation driven oncogenic events involving both IGH loci and proto-oncogenes BCL2 and BCL3. Importantly, the IGH;BCL3 translocation was characterized by the duplication of the genomic region adjacent to BCL3, containing a major DNA repair factor, ERCC2.

Electronic supplementary material

The online version of this article (doi:10.1186/s13039-015-0203-y) contains supplementary material, which is available to authorized users.

Similar clinical features in follicular lymphomas with and without breaks in the BCL2 locus

Approximately 15% of follicular lymphomas (FLs) lack breaks in the BCL2 locus. The aim of this study was to better define molecular and clinical features of BCL2-breakpoint/t(14;18)-negative FLs. We studied the presence of BCL2, BCL6 and MYC breaks by fluorescence in situ hybridization and the expression of BCL2, MUM1, CD10, P53 and Ki67 in large clinical trial cohorts of 540 advanced-stage FL cases and 116 early-stage disease FL patients treated with chemotherapy regimens and radiation, respectively. A total of 86% and 53% of advanced- and early-stage FLs were BCL2-breakpoint-positive, respectively. BCL2 was expressed in almost all FLs with BCL2 break and also in 86% and 69% of BCL2-breakpoint-negative advanced- and early-stage FLs, respectively. CD10 expression was significantly reduced in BCL2-breakpoint-negative FLs of all stages and MUM1 and Ki67 expression were significantly increased in BCL2-break-negative early-stage FLs. Patient characteristics did not differ between FLs with and without BCL2 breaks and neither did survival times in advanced-stage FLs. These results suggest that the molecular profile differs to some extent between FLs with and without BCL2 breaks and support the notion that FLs with and without BCL2 breaks belong to the same lymphoma entity.

Malignant lymphoma of the conjunctiva

Conjunctival lymphomas constitute 25% of all ocular adnexal lymphomas. The majority are B-cell non-Hodgkin lymphomas (NHLs) (98%), whereas conjunctival T-cell NHLs are rare (2%). The most frequent subtype of conjunctival B-cell lymphoma is extranodal marginal zone lymphoma (EMZL; 81%), followed by follicular lymphoma (8%), diffuse large B-cell lymphoma (3%), and mantle cell lymphoma (3%). Extranodal marginal zone lymphoma occurs slightly more often in women and, along with follicular lymphoma, presents late in the seventh decade of life, whereas diffuse large B-cell lymphoma and especially mantle cell lymphoma have a predilection for the male gender and typically present in the eighth decade. Extranodal marginal zone lymphoma and follicular lymphoma present most frequently in the forniceal and bulbar conjunctiva. Conjunctival diffuse large B-cell lymphoma, mantle cell lymphoma and T-cell NHLs are characterized by a short duration of symptoms before the first ophthalmologic consultation. External beam radiotherapy is the treatment of choice for extranodal marginal zone lymphoma and follicular lymphoma, whereas diffuse large B-cell lymphoma, mantle cell lymphoma, and T-cell NHLs are mainly treated with chemotherapy. Conjunctival T-cell NHLs are associated with a particularly poor prognosis, with 50% of patients having progression or recurrence during a 1-year follow-up period.

Die-hard survivors: heterogeneity in apoptotic thresholds may underlie chemoresistance

The unmatched efficacy of microtubule-targeting agents (MTAs) as chemotherapeutics was once assumed to originate from their impact on mitotic processes; however, this misconception is being eroded by amassing data that MTAs instead target interphase functions in patients' tumors. What remains murky is how MTAs target malignant cells over non-malignant ones if proliferation rates do not distinguish them. In many instances, malignant cells are actually more 'primed' for apoptosis than non-malignant ones. Nevertheless, even if most cells within the tumor are more apoptosis-susceptible than those in healthy tissues, there likely exist small subpopulations of apoptosis-resistant clones that engender incomplete responses to MTAs and relapse. Therefore, intratumor heterogeneity in terms of proximity to the apoptotic threshold must be better understood to facilitate the design of chemotherapeutic regimens, which may benefit from including drugs like BH3 mimetics that help in lowering the apoptotic threshold of tumor cells within these chemoresistant subpopulations.

Immunohistochemical markers in lymphoid malignancies: Protein correlates of molecular alterations

Histomorphology, immunohistochemistry (IHC), and genetics are essential tools for the evaluation and classification of lymphoid malignancies. Advances in diagnostic techniques include the development of immunohistochemical assays that can serve as surrogates for genetic tests. We review the performance of a select subset of assays that detect the aberrant expression of onco-proteins secondary to chromosomal translocations (MYC; BCL2), somatic mutations (BRAF V600E; NOTCH1), and gene copy number gains (CD274 (encoding PD-L1); PDCD1LG2 (encoding PD-L2)) in fixed tissue biopsy sections. We discuss the limitations of IHC, but also its primary advantage over genetics; specifically, its ability to assess the final, common phenotypic consequences of a multitude of genetic and non-genetic events that influence protein expression. The information provided by IHC and genetic testing are thus intimately related; surgical pathologists will increasingly need to interpret and integrate the results of both to provide a comprehensive assessment of tumor biology and guide therapy.

Inter- and intratumoral heterogeneity of BCL2 correlates with IgH expression and prognosis in follicular lymphoma

Most follicular lymphomas (FLs) are genetically defined by the t(14;18)(q32;q21) translocation that juxtaposes the BCL2 gene to the immunoglobulin heavy chain (IgH) 3' regulatory regions (IgH-3'RRs). Despite this recurrent translocation, FL cases are heterogeneous in terms of intratumoral clonal diversity for acquired mutations and variations in the tumor microenvironment. Here we describe an additional mechanism that contributes to inter- and intratumoral heterogeneity in FLs. By applying a novel single-molecule RNA fluorescence-based in situ hybridization (FISH) technique to detect mRNA molecules of BCL2 and IgH in single cells, we found marked heterogeneity in the number of BCL2 mRNA transcripts within individual lymphoma cells. Moreover, BCL2 mRNA molecules correlated with IgH mRNA molecules in individual cells both in t(14;18) lymphoma cell lines and in patient samples. Consistently, a strong correlation between BCL2 and IgH protein levels was found in a series of 205 primary FL cases by flow cytometry and immunohistochemistry. Inter- and intratumoral heterogeneity of BCL2 expression determined resistance to drugs commonly used in FL treatment and affected overall survival of FL patients. These data demonstrate that BCL2 and IgH expressions are heterogeneous and coregulated in t(14;18)-translocated cells, and determine the response to therapy in FL patients.

Lack of expression of TUBB3 characterizes both BCL2-positive and BCL2-negative follicular lymphoma

Follicular lymphoma is characterized by aberrant BCL2 expression, a feature that is exploited for diagnostic purposes. However, a certain percentage of follicular lymphomas might be BCL2-negative by immunohistochemistry, increasing the difficulties in differentiating them from follicular hyperplasia. The expression of TUBB3 has been recently reported as negative in a small series of follicular lymphomas. We have therefore tested a larger series, including 61 BCL2-positive and 25 BCL2-negative cases, and compared them with 61 reactive lymphoid tissues. First, a subjective score of TUBB3 staining was applied, showing that it was consistently positive in reactive germinal centers, while most follicular lymphomas were negative; in fact, only 10/61 (16%) BCL2-positive and 1/25 (4%) BCL2-negative cases showed a positive staining for TUBB3, while 58/61 (95%) of tissues with follicular hyperplasia were positive. The application of a standardized scoring system to a large number of follicles, based on virtual slides, demonstrated that reactive lymphoid tissues had a significantly higher number of TUBB3-positive follicles both compared with BCL2-positive cases and to BCL2-negative cases. Our data support the use of TUBB3 staining in differentiating follicular lymphoma, including BCL2-negative cases, from follicular hyperplasia.

Cell growth in aggregates determines gene expression, proliferation, survival, chemoresistance, and sensitivity to immune effectors in follicular lymphoma

Lymphomas grow as dense aggregates in patients, but whether this spatial organization affects lymphoma cell biology is unknown. We grew follicular lymphoma (FL) cells in vitro as multicellular aggregates of lymphoma cells to investigate this question. Gene expression analysis revealed that 612 genes were differentially expressed when cells grew in multicellular aggregates of lymphoma cells rather than in suspension. These genes correspond to several GO biological processes, such as hypoxia, activation of NF-κB pathway, and negative regulation of cell cycle, a gene signature also found in the transcriptomes from FL biopsies. Pimonidazole staining, HIF-1A accumulation, and VEGFA release confirmed that cells in multicellular aggregates of lymphoma cells actually respond to hypoxia. In adaptation to such conditions, they also displayed an activated NF-κB pathway and a quiescent status far more frequently than in suspension. When cultured in three dimensions, FL cells display resistance to doxorubicin and bendamustine, two drugs largely used in FL therapy, compared to FL cultured in suspension. Finally, multicellular aggregates of lymphoma cells were also found to be less sensitive to purified natural killer cells. To conclude, our study shows that in FL, spatial organization results in dramatic changes in FL biology, including gene expression, proliferation, drug resistance, and immune escape.

The Utility of Immunohistochemistry for Providing Genetic Information on Tumors

With advances in immunohistochemical technology and growing knowledge of the molecular genetics of tumors, immunohistochemistry is playing an increasingly important role in providing genetic information for tumors. Specific chromosomal translocations can be demonstrated through detection of the protein product of one of the genes involved in gene fusion (such as BCL2, cyclin D, and ALK). Some mutations can be detected by (1) aberrant localization of the protein product (such as β-catenin and nucleophosmin), (2) abnormal accumulation of the protein product as a result of stabilization of the protein (such as p53), and (3) mutation-specific antibodies directed against the mutant protein (such as isocitrate dehydrogenase gene R132H mutation, epidermal growth factor receptor gene L858R and exon 19 deletion mutations, and BRAF gene V600E mutation). Gene deletion or loss of function can be demonstrated by the loss of immunostaining for the protein product (such as mismatch repair proteins in microsatellite-unstable tumors, E-cadherin in lobular carcinoma of the breast, and INI1 in rhabdoid tumors, atypical teratoid/rhabdoid tumors, and epithelioid sarcomas). Gene amplification can be demonstrated by overexpression of the protein product (such as HER2 in breast and gastric cancers, and MDM2 or CDK4 in well-differentiated/dedifferentiated liposarcomas). Viruses associated with tumors can be demonstrated directly (such as Epstein-Barr virus latent membrane protein-1 in Hodgkin lymphomas, human herpesvirus 8 in Kaposi sarcomas, and Merkel cell polyomavirus in Merkel cell carcinomas) or by a surrogate marker (such as p16 in human papillomavirus infection). In this review, examples are given to illustrate the principles and pitfalls of these applications.

The BCL2 E17 and SP66 antibodies discriminate 2 immunophenotypically and genetically distinct subgroups of conventionally BCL2-"negative" grade 1/2 follicular lymphomas

Follicular lymphoma (FL) is characterized by the translocation t(14;18)(q32;q21) resulting in constitutive overexpression of BCL2. However, in 10% to 15% of FL grade 1/2, immunohistochemical staining for BCL2 remains negative. To analyze the incidence of BCL2 negativity and the underlying molecular mechanisms in FL grade 1/2, BCL2 expression was investigated with 3 antibodies (clones 100D5, E17, SP66). The presence of a break in the BCL2 locus was determined by fluorescence in situ hybridization. The region of the BCL2 gene where the epitope of the standard BCL2 antibody resides was sequenced. Twenty-two (9.2%) of 240 identified cases of FL grade 1/2 were negative with the standard BCL2 antibody. Of these, 12 cases (55%) carried a break in the BCL2 gene locus, which, in all but one case, correlated with BCL2 expression using the alternative antibodies E17 and SP66 and with missense mutations of BCL2. Ten (45%) of the 22 cases had an intact BCL2 gene locus; 2 cases carried a BCL6/IGH translocation. All 10 cases were negative for the E17/SP66 antibodies and showed a wild-type sequence of BCL2. Six of these showed an aberrant phenotype, with CD10 negativity (30%) or CD23 expression (30%). In summary, the alternative E17/SP66 antibodies identify 2 immunohistochemically and genetically distinct subgroups of BCL2-"negative" FL grade 1/2.

Another look at follicular lymphoma: immunophenotypic and molecular analyses identify distinct follicular lymphoma subgroups

AIMS

The aim of this study was to analyse the immunophenotypic and molecular features of a large series of follicular lymphomas, focusing in particular on atypical cases that fail to express CD10 and/or bcl-2. Such cases present diagnostic pitfalls, especially with regard to the differential diagnosis from follicular hyperplasia and marginal zone B-cell lymphoma. Therefore, we also included an immunohistochemical evaluation of stathmin, which is strongly expressed by germinal centre B cells, as a putative new marker for follicular lymphomas, particularly those with an atypical phenotype.

METHODS AND RESULTS

Two hundred and five follicular lymphomas were investigated with immunohistochemistry and fluorescence in-situ hybridization (FISH). The use of three distinct anti-bcl-2 antibodies together with CD10 expression data and FISH analysis for bcl-2 and bcl-6 rearrangements allowed subclassification of follicular lymphoma into four distinct subgroups: (i) CD10-positive/bcl-2-positive, (ii) CD10-positive/bcl-2-negative, (iii) CD10-negative/bcl-2-positive, and (iv) CD10-negative/bcl-2-negative. All cases were bcl-6-positive. STMN1 (stathmin) was shown to be helpful in diagnosing bcl-2-negative and/or CD10-negative follicular lymphomas, and in their distinction from marginal zone B-cell lymphoma.

CONCLUSIONS

Combined immunohistological and molecular analyses reveal that follicular lymphomas showing an atypical immunophenotypic and molecular profile exist, and we demonstrate that STMN1 represents a novel useful diagnostic marker for these.

Nodal and leukemic small B-cell neoplasms

The small B-cell neoplasms represent some of the most frequently encountered lymphoproliferative disorders in routine surgical pathology practice. This report reviews the current diagnostic criteria for classifying small B-cell neoplasms and distinguishing them from newly recognized precursor conditions that do not appear to represent overt lymphomas. Newly available immunohistochemical stains and molecular studies that may assist in the diagnosis and classification of these neoplasms are also discussed.

Variation in BCL2 protein expression in follicular lymphomas without t(14;18) chromosomal translocations

AIM

The hallmark of follicular lymphoma is the t(14;18)(q32;q21) chromosomal translocations that lead to deregulation of BCL2 expression in tumour cells. However, not all cases of follicular lymphoma express BCL2, nor is the t(14;18) translocation always present. Follicular lymphomas lacking the BCL2 rearrangement are less well studied with regards to their immunohistochemical and molecular features. This study aims to investigate the BCL2 protein expression pattern in t(14;18) negative follicular lymphomas.

METHODS

BCL2 protein expression pattern was analysed in 26 cases of t(14;18) negative follicular lymphoma [determined by fluorescence in situ hybridisation (FISH)], using antibodies against two-different epitopes, i.e., the widely-used antibody BCL2/124 and an alternative antibody E17.

RESULTS

Two of the t(14;18) negative cases showed evidence of BCL2 amplification and trisomy 18. A total of 13 cases (50%) lacked BCL2 expression. In 10 cases (38%) the expression was heterogeneous and in only three cases (12%) the BCL2 expression was strongly positive. These cases could thus be subdivided into three subgroups: Group I, normal BCL2 genes (i.e., no evidence of translocation or amplification), and BCL2 protein negative; Group II, normal BCL2 genes but BCL2 protein positive; and Group III, presence of other genetic alterations, i.e., BCL2 amplification and trisomy 18, and BCL2 protein positive.

CONCLUSIONS

This study suggests that it may be possible on the basis of staining to predict that the t(14;18) translocation is absent if a case is either negative for BCL2 protein with different antibodies or has heterogeneous BCL2 expression, possibly acquired through a physiological process of differentiation.

B Cells Behaving Badly: A Better Basis to Behold Belligerence in B-Cell Lymphomas

A plethora of genetic abnormalities has been described in B-cell lymphomas, some of which arise when physiologic mechanisms involved in the generation of immunologic diversity go awry. Several different lymphoma types, such as follicular lymphoma (FL), mantle cell lymphoma (MCL), and Burkitt lymphoma (BL), are associated with hallmark translocations that occur as a consequence of these errors (t(14;18)(q32;q21), t(11;14)(q13;q32), and t(8;14)(q24;q32), respectively); however, none of these associations is absolute and none is completely diagnostically specific or sensitive. The advantages and limitations of a variety of different testing strategies in the 2 most common lymphomas, FL and diffuse large B-cell lymphoma (DLBCL), are reviewed herein, including an evaluation of the role of PCR-based approaches, FISH, and more nascent genomic technologies. The use of immunophenotypic strategies that may potentially provide, albeit imperfectly, more user-friendly surrogates for underlying genetic aberrations and cell-of-origin designations derived from gene-expression profiling analyses are also discussed. Finally, a newly designated category of lymphoma with features intermediate between DLBCL and BL is appraised, highlighting the central role of genetic analysis in this diagnostic gray zone.

In situ follicular lymphoma with progressive transformation of the germinal centers confirmed by laser capture microdissection, IGH gene rearrangement analysis, and fluorescence in situ hybridization for t(14;18)

The authors report an unusual case of in situ follicular lymphoma associated with progressive transformation of the germinal centers. The patient was a 74-year-old Chinese woman with sequential lymphadenopathy in the right and left cervical regions over a period of 2 months. The first biopsy revealed in situ follicular lymphoma with progressive transformation of germinal centers, and the biopsy of the second lymph node led to a diagnosis of in situ follicular lymphoma. The immunophenotype, polymerase chain reaction amplification of the immunoglobulin heavy chain gene, and fluorescence in situ hybridization for t(14;18) were analyzed in each biopsy specimen, which showed both specimens to have t(14;18)(q32;q21) and revealed progression from polyclonality to monoclonality. These findings suggest a case of multicentric in situ follicular lymphoma and provide new insights into the pathogenesis of this disease.

Follicular lymphoma: stillSix characters in search of an author?

Follicular lymphoma (FL) is regarded as a distinct entity in the literature as well as in the 2008 edition of the WHO classification of tumours of haematopoietic and lymphoid tissues. Nevertheless, there are still several issues that are matters of controversy such as the grading system or the exact biological location of grade 3B FL. This makes FL somewhat like the Six characters in search of an author of Pirandello's comedy. Here, we revise the morphology and pathobiology of FL by highlighting both the areas remaining critical and future perspectives. This review was inspired by the reappraisal of Professor Lennert's personal archive that represents a unique legacy for the entire scientific community.

Functions and uses of immunohistochemical stains in cutaneous infiltrates of hematopoietic origin: a review for the practicing dermatologist

BACKGROUND

Immunohistochemical stains, particularly those for cutaneous lymphomas, have similar-sounding names, which may lead to confusion among dermatologists who are not well versed in the terminology of the tools used for pathologic diagnosis. Also aiding in this is the fact that some familiar stains are constantly investigated for novel utility in different tumors, and a plethora of new stains regularly emerge in the peer-reviewed literature.

OBJECTIVE

To review the major stains encountered in dermatopathologic reports for cutaneous lymphomas. A select number of other stains are reviewed that are either new and under investigation in several cutaneous processes or have a new use described in recent reports.

METHODS

The peer-reviewed literature was searched and analyzed for the accepted purposes of using these markers.

RESULTS

All pertinent findings for these immunostains are reported with the purpose of educating the dermatology community.

CONCLUSION

This review serves as a reference to clarify potentially confusing immunohistochemical stains.

The essential role of evasion from cell death in cancer

The link between evasion of apoptosis and the development of cellular hyperplasia and ultimately cancer is implicitly clear if one considers how many cells are produced each day and, hence, how many cells must die to make room for the new ones (reviewed in Raff, 1996). Furthermore, cells are frequently experiencing noxious stimuli that can cause lesions in their DNA and faults in DNA replication can occur during cellular proliferation. Such DNA damage needs to be repaired efficiently or cells with irreparable damage must be killed to prevent subsequent division of aberrant cells that may fuel tumorigenesis (reviewed in Weinberg, 2007). The detection of genetic lesions in human cancers that activate prosurvival genes or disable proapoptotic genes have provided the first evidence that defects in programmed cell death can cause cancer (Tagawa et al., 2005; Tsujimoto et al., 1984; Vaux, Cory, and Adams, 1988) and this concept was proven by studies with genetically modified mice (Egle et al., 2004b; Strasser et al., 1990a). It is therefore now widely accepted that evasion of apoptosis is a requirement for both neoplastic transformation and sustained growth of cancer cells (reviewed in Cory and Adams, 2002; Hanahan and Weinberg, 2000; Weinberg, 2007). Importantly, apoptosis is also a major contributor to anticancer therapy-induced killing of tumor cells (reviewed in Cory and Adams, 2002; Cragg et al., 2009). Consequently, a detailed understanding of apoptotic cell death will help to better comprehend the complexities of tumorigenesis and should assist with the development of improved targeted therapies for cancer based on the direct activation of the apoptotic machinery (reviewed in Lessene, Czabotar, and Colman, 2008).

Germline variation in apoptosis pathway genes and risk of non-Hodgkin's lymphoma

BACKGROUND

The t(14;18)(q32;q21) translocation is the most commonly observed chromosomal translocation in non-Hodgkin's lymphoma (NHL), resulting in constitutive Bcl-2 expression and apoptosis inhibition. In addition, germline variation in both BCL2L11 (BIM) and CASP9, known regulators of apoptosis, has recently been linked to NHL risk. We conducted a comprehensive evaluation of 36 apoptosis pathway genes with risk of NHL.

METHODS

We genotyped 226 single-nucleotide polymorphisms (SNP) from 36 candidate genes in a clinic-based study of 441 newly diagnosed NHL cases and 475 frequency-matched controls. We used principal components analysis to assess gene-level associations, and logistic regression to assess SNP-level associations. MACH was used for imputation of SNPs in BCL2L11 and CASP9.

RESULTS

In gene-level analyses, BCL2L11 (P = 0.0019), BCLAF1 (P = 0.0097), BAG5 (P = 0.026), and CASP9 (P = 0.0022) were associated with NHL risk after accounting for multiple testing (tail strength, 0.38; 95% confidence interval, 0.05-0.70). Two of the five BCL2L11 tagSNPs (rs6746608 and rs12613243), both genotyped BCLAF1 tagSNPs (rs797558 and rs703193), the single genotyped BAG5 tagSNP (rs7693), and three of the seven genotyped CASP9 tagSNPs (rs6685648, rs2020902, and rs2042370) were significant at P < 0.05. We successfully imputed BCL2L11 and CASP9 SNPs previously linked to NHL, and replicated all four BCL2L11 and two of three CASP9 SNPs.

CONCLUSION

We replicated the association of BCL2L11 and CASP9 with NHL risk at the gene and SNP level, and identified novel associations with BCLAF1 and BAG5.

IMPACT

Closer evaluation of germline variation of genes in the apoptosis pathway with risk of NHL and its subtypes is warranted.

Rearrangement of MYC Is Associated With Poor Prognosis in Patients With Diffuse Large B-Cell Lymphoma Treated in the Era of Rituximab

Purpose

Rearrangement of MYC occurs in a proportion of diffuse large B-cell lymphomas (DLBCL), where they may be associated with an adverse clinical outcome. The aim of this study was to determine the frequency of MYC translocations in DLBCL and their prognostic impact in the era of cyclophosphamide, doxorubicin, vincristine, and prednisone plus rituximab (CHOP-R) therapy.

Patients and Methods

Three hundred three patients with previously untreated DLBCL, with no evidence of underlying follicular lymphoma, were investigated using immunohistochemistry and interphase fluorescent in situ hybridization for MYC, BCL6, and t(14;18)/BCL2 rearrangements. All patients (median age, 71.1 years; range, 23 to 96 years) were treated when CHOP-R was standard therapy for DLBCL and observed for a maximum of 4 years. Overall survival (OS) at 3 years was 49% (95% CI, 42% to 56%).

Results

MYC rearrangements were demonstrated in 35 (14%) of 245 biopsies with data available. Of these, 26 (74%) also had a t(14;18), 10 (26%) were BCL6 and MYC rearranged, and seven had all three abnormalities. Only age, International Prognostic Index, and MYC rearrangement retained prognostic significance in the final model. OS was significantly worse for patients with rearrangement of MYC (survival probability at 2 years = 0.35 in v 0.61 in the nonrearranged group).

Conclusion

The presence of a MYC rearrangement is a strongly adverse prognostic factor in CHOP-R–treated patients and can be used in combination with patients' age and IPI to accurately predict clinical outcome. In DLBCL, rearrangement of MYC is rarely found as the sole genetic abnormality and the poor prognosis of these patients is likely to reflect a synergistic effect alongside deregulation of BCL6 or BCL2.

Pseudonegative BCL2 protein expression in a t(14;18) translocation positive lymphoma cell line: a need for an alternative BCL2 antibody

AIM

The t(14;18)(q32;q21) chromosomal translocation induces BCL2 protein expression in most follicular lymphomas. However, a small number of cases lack BCL2 expression despite carrying the t(14;18)(q32;q21) translocation. This study aims to explore the mechanism accounting for the lack of BCL2 protein expression when the t(14;18) translocation is present.

METHODS

BCL2 expression in the t(14;18) positive cell lines FL18, Karpas-422, SU-DHL-4 and SU-DHL-6, was analysed by Western blotting and by immunohistochemistry using two different antibodies. FISH analysis was performed to confirm the cytogenetic changes in the cell lines and real time quantitative PCR was used to evaluate the BCL2 mRNA level. Sequence analysis of translocated BCL2 was performed on FL18, Karpas-422, SU-DHL-4 and SU-DHL-6 cell lines.

RESULTS

In FL18, Karpas-422, and SU-DHL-4, the BCL2 mRNA level correlated with the BCL2 protein expression. In contrast, BCL2 protein was not detected in SU-DHL-6 line using standard anti-BCL2 antibody (BCL2/124), despite the presence of the t(14;18) translocation and high level of mRNA. cDNA sequencing of translocated BCL2 showed three mutations in the SU-DHL-6 cell line, one of which resulted in an amino acid substitution (I48F) in the region recognised by the standard BCL2 antibody, whereas the other two were silent mutations at aa71 and aa72. Interestingly, when BCL2 expression was tested with an alternative antibody, E17, the protein was detected in SU-DHL-6, suggesting that the 'negativity' of SU-DHL-6 line for BCL2 using the standard antibody is spurious. Amino acid changes were found in Karpas-422 (G47D, P59L) and SU-DHL-4 (P59T, S117R) but these did not affect BCL2 detection.

CONCLUSIONS

This study suggests that some somatic mutations of the translocated BCL2 gene may prevent epitope recognition by BCL2 antibodies, and hence cause false negative expression using the standard antibody. It is recommended that in practice all BCL2 negative cases should routinely be stained with an alternative antibody to prevent false negativity.

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.

Lymphomas with concurrent BCL2 and MYC translocations: the critical factors associated with survival

BCL2 and MYC are oncogenes commonly deregulated in lymphomas. Concurrent BCL2 and MYC translocations (BCL2(+)/MYC(+)) were identified in 54 samples by karyotype and/or fluorescence in situ hybridization with the aim of correlating clinical and cytogenetic characteristics to overall survival. BCL2(+)/MYC(+) lymphomas were diagnosed as B-cell lymphoma unclassifiable (BCLU; n = 36) with features intermediate between Burkitt lymphoma and diffuse large B-cell lymphoma (DLBCL); DLBCL (n = 17), or follicular lymphoma (n = 1). Despite the presence of a t(14;18), 5 cases were BCL2 protein-negative. Nonimmunoglobulin gene/MYC (non-IG/MYC) translocations occurred in 24 of 54 cases (44%) and were highly associated with DLBCL morphology (P < .001). Over a median follow-up of 5.3 years, 6 patients remained in remission and 32 died within 6 months of the MYC(+) rearrangement, irrespective of whether MYC(+) occurred at diagnosis (31 of 54) or transformation (23 of 54; P = .53). A non-IG/MYC translocation partner, absent BCL2 protein expression and treatment with rituximab-based chemotherapy, were associated with a more favorable outcome, but a low International Prognostic Index score and DLBCL morphology were independent predictors of overall survival. A comprehensive cytogenetic analysis of BCL2 and MYC status on all aggressive lymphomas may identify a group of high-risk patients who may benefit from chemotherapeutic regimens that include rituximab and/or BCL2-targeted therapy.