B-Lymphoblastic Lymphomas Evolving from Follicular Lymphomas Co-Express Surrogate Light Chains and Mutated Gamma Heavy Chains

SMARCA4 and SMARCA2 co-deficiency: An uncommon molecular signature defining a subset of rare, aggressive and undifferentiated malignancies associated with defective chromatin remodeling

Genetic mutations and epigenetic modifications affecting multiple cancer-related genes occur synergistically to drive tumorigenesis. Across a wide spectrum of cancers, pathogenic changes have been identified in members of the SWItch/Sucrose Non-Fermentable complex including its two catalytic subunits, SMARCA4 and SMARCA2. During cancer development, it is not uncommon to lose the function of either SMARCA4 or SMARCA2, however, loss of both together has been reported to be synthetic lethal and therefore unexpected. Co-deficiency of SMARCA4 and SMARCA2 occurs as a pathognomonic feature of the early-onset ovarian cancer Small-cell carcinoma of the ovary, hypercalcemic type. The loss of both catalytic subunits is also described in other rare undifferentiated neoplasms including Thoracic SMARCA4-deficient undifferentiated tumors, Malignant rhabdoid tumors and dedifferentiated or undifferentiated carcinomas, predominantly of lung, gastrointestinal, and endometrial origin. This review provides the first extensive characterization of cancers with concurrent SMARCA4 and SMARCA2 loss through the discussion of shared clinical and molecular features. Further, we discuss the mechanisms triggering the loss of catalytic activity, the cellular processes that are dysfunctional as a consequence, and finally, current therapeutic candidates which may selectively target these cancers.

Case report: Mutation evolution in a patient with TdT positive high grade B cell lymphoma with MYC and BCL2 rearrangements following the treatment of concurrent follicular lymphoma and diffuse large B-cell lymphoma

BACKGROUND

Concurrent follicular lymphoma (FL) and diffuse large B-cell lymphoma (DLBCL)was reported in some studies, while the diagnosis of TdT (terminal deoxynucleotydil transferase) positive high grade B cell lymphoma (HGBL) with MYC and BCL2 rearrangements ("double hit") transformed from FL/DLBCL has been rarely reported. Herein, we described the clinical features and mutation profiles of a case diagnosed with TdT positive "double hit" HGBL following the treatment of FL/DLBCL.

CASE PRESENTATION

This is a 43-year-old Chinese man who was diagnosed with low grade FL (account for 80%) combined with DLBCL (20%) at a stage of IVB. The patient presented with BCL2/IGH translocation without MYC rearrangement, as well as the expressions of CD20, CD19, CD10 and BCL2 at the initial diagnosis of FL/DLBCL. MYC rearrangement and TdT expression occurred after the treatment. The targeted sequencing revealed mutations in KMT2D, FOXO1, CREBBP, ATM, STAT6, BCL7A, DDX3X, MUC4, FGFR3, ARID5B, DDX11 and PRKCSH genes were the co-mutations shared by the FL/DLBCL and TdT positive "double hit" HGBL, while CCND3, BIRC6, ROBO1 and CHEK2 mutations specifically occurred after the treatment. The overall survival time was 37.8 and 17.8 months after the initial diagnosis of FL/DLBCL and TdT positive "double hit" HGBL, respectively.

CONCLUSION

This study reports a rare case of TdT positive "double hit" HGBL following the treatment of concurrent FL/DLBCL and highlights the mutation characteristics. Collectively, this study will help enrich the knowledge of TdT positive "double hit" HGBL transformed from FL/DLBCL.

Aggressive B-cell non-Hodgkin lymphomas: a report of the lymphoma workshop of the 20th meeting of the European Association for Haematopathology

Aggressive B-cell non-Hodgkin lymphomas are a heterogeneous group of diseases and our concepts are evolving as we learn more about their clinical, pathologic, molecular genetic features. Session IV of the 2020 EAHP Workshop covered aggressive, predominantly high-grade B-cell lymphomas, many that were difficult to classify. In this manuscript, we summarize the features of the submitted cases and highlight differential diagnostic difficulties. We specifically review issues related to high-grade B-cell lymphomas (HGBCLs) with MYC and BCL2 and/or BCL6 rearrangements including TdT expression in these cases, HGBCL, not otherwise specified, large B-cell lymphomas with IRF4 rearrangement, high-grade/large B-cell lymphomas with 11q aberration, Burkitt lymphoma, and pleomorphic mantle cell lymphoma. Since the workshop, the 5th edition of the WHO Classification for Haematolymphoid Tumours (WHO-HAEM5) and International Consensus Classification (ICC) 2022 were published. We endeavor to use the updated terminology.

B-lymphoblastic leukemia/lymphoma with MYC and BCL2 gene rearrangements shows evidence for clonal evolution and mitotic recombination

BACKGROUND

B-lymphoblastic leukemia/lymphomas (B-ALL/LBL) are uncommon neoplasms that may be associated with a variety of cytogenetic and molecular changes. The mechanisms by which these changes arise have not been fully described.

AIMS/PURPOSE

This report describes an unusual case of B-ALL/LBL with complex clonal evolution that includes BCL2 and MYC gene rearrangements.

METHODS

Immunophenotyping was performed by immunohistochemistry and flow cytometry. Traditional G-band karyotyping was accompanied by fluorescence in-situ hybridization (FISH) using break-apart and dual fusion probes. Single nucleotide polymorphisms were assessed using a high-density DNA microarray.

RESULTS

The karyotype of the blasts showed reciprocal translocation of chromosomes 4 and 18, reciprocal translocation of chromosomes 8 and 14 with two copies of the oncogenic translocation derivative(14)t(8;14), and no normal chromosome 14. FISH studies showed complex IGH-BCL2 and IGH-MYC fusion signals.

CONCLUSIONS

A clonal evolution model involving multiple chromosomal translocations and mitotic recombination is postulated to account for the karyotype, FISH, and microarray results but leaves unresolved the exact order of the evolutionary changes.

Blastoid B-Cell Neoplasms: Diagnostic Challenges and Solutions

Blastoid B-cell neoplasms mainly include B-lymphoblastic leukemia/lymphoma (B-ALL), blastoid mantle cell lymphoma, and high-grade B-cell lymphoma with blastoid morphologic features (blastoid HGBL). Distinguishing blastoid HGBL from B-ALL can be challenging and we previously developed six-point flow cytometry-focused and three-point immunohistochemistry-focused scoring systems to aid in differential diagnosis. However, the six-point scoring system was derived from bone marrow cases and occasional cases may have a misleading score using either system. In this study, we assessed 121 cases of blastoid-HGBL (37 BM and 84 extramedullary) to validate the six-point scoring system in all tissue types and to further compare the two scoring systems. Compared with 47 B-ALL cases enriched for CD34-negative neoplasm, the 121 blastoid-HGBL cases showed distinctive pathologic features. The six-point scoring system showed a sensitivity of 100%. A comparison of the two scoring systems in blastoid HGBL (n = 64) and B-ALL (n = 37) showed a concordance score rate of 88%. Thirteen cases showed misleading scores, including five HGBL and eight B-ALL, and the diagnosis was further validated by gene transcriptome profiling. Twelve of thirteen cases had discordant scores between the two scoring systems. Simultaneous employment of both scoring systems improved the accuracy of classification of blastoid B-cell neoplasms to 99%. In conclusion, the previously defined six-point scoring system showed an excellent performance regardless of the tissue origin. Using both scoring systems together improves the accuracy of classification of blastoid B-cell neoplasms. Cases with discordant scores between the two scoring systems were extremely challenging neoplasms and classification required correlation with all available clinical and genetic features.

Transformation of diffuse large B-cell lymphoma to lymphoblastic lymphoma

Transformations in diffuse large B-cell lymphoma (DLBCL) are extremely rare. Here, we are presenting a very rare case of DLBCL transforming into lymphoblastic lymphoma (LBL) diagnosed by fine-needle aspiration cytology (FNAC) and flow cytometry. A 31-year old male on antiretroviral therapy and a known case of diffuse large B-cell lymphoma diagnosed 1 year back on cervical lymphadenopathy, presented with left axillary swelling for 3 months. FNAC and Flow cytometry were performed from the left axillary swelling which confirmed the diagnosis of LBL.

Mutational Landscape of TdT+ Large B-cell Lymphomas Supports Their Distinction From B-lymphoblastic Neoplasms: A Multiparameter Study of a Rare and Aggressive Entity

In the current World Health Organization classification, terminal deoxynucleotidyl transferase (TdT) expression in a high grade/large cell B-cell lymphoma (LBCL) indicates a B-lymphoblastic lymphoma/leukemia (B-LBL), although TdT expression in what appear to be mature LBCL or following mature B-cell neoplasms is reported. The frequency of TdT+ LBCL, how to best categorize these cases, and their clinicopathologic features, molecular landscape, and relationship to classic B-LBL remain to be better defined. TdT expression was therefore assessed in 258 LBCL and the results correlated with the cytologic, phenotypic, and cytogenetic findings. Targeted mutational analysis, review of prior biopsies, and assessment of clinical associations was performed in the 6 cases with >10% TdT+ cells. All 6 TdT+ LBCL were blastoid-appearing, CD34-, MYC+, BCL2+, and had MYC rearrangements (R) (5/6 with BCL2 and/or BCL6-R). 5/6 had a prior TdT- LBCL and/or follicular lymphoma and all had an aggressive course. Fifteen nonsynonymous variants in 11 genes were seen in the 4/5 tested cases with mutations. TdT+ and TdT- areas in 1 case showed identical mutations. The mutational profiles were more like those reported in germinal center B-cell type-diffuse LBCL rather than B-LBL. Evolution from preceding TdT- lymphomas was nondivergent in 1/3 tested cases and partially divergent in 2. The clinicopathologic and cytogenetic features of these 6 cases were similar to those found in a meta-analysis that included additional cases of TdT+ LBCL or B-LBL following follicular lymphoma. Thus, TdT+, CD34- large B-cell neoplasms with MYC rearrangements and often a "double hit" are rare, frequently a transformational event and aggressive but are distinct from classic B-LBL.

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.

Mantle cell lymphomas with concomitant MYC and CCND1 breakpoints are recurrently TdT positive and frequently show high-grade pathological and genetic features

Chromosomal breakpoints involving the MYC gene locus, frequently referred to as MYC rearrangements (MYC - R+), are a diagnostic hallmark of Burkitt lymphoma and recurrent in many other subtypes of B-cell lymphomas including follicular lymphoma, diffuse large B-cell lymphoma and other high-grade B-cell lymphomas and are associated with an aggressive clinical course. In remarkable contrast, in MCL, only few MYC - R+ cases have yet been described. In the current study, we have retrospectively analysed 16 samples (MYC - R+, n = 15, MYC - R-, n = 1) from 13 patients and describe their morphological, immunophenotypic and (molecular) genetic features and clonal evolution patterns. Thirteen out of fifteen MYC - R+ samples showed a non-classical cytology including pleomorphic (centroblastic, immunoblastic), anaplastic or blastoid. MYC translocation partners were IG-loci in 4/11 and non-IG loci in 7/11 analysed cases. The involved IG-loci included IGH in 3 cases and IGL in one case. PAX5 was the non-IG partner in 2/7 patients. The MYC - R+ MCL reported herein frequently displayed characteristics associated with an aggressive clinical course including high genomic-complexity (6/7 samples), frequent deletions involving the CDKN2A locus (7/10 samples), high Ki-67 proliferation index (12/13 samples) and frequent P53 expression (13/13 samples). Of note, in 4/14 samples, SOX11 was not or only focally expressed and 3/13 samples showed focal or diffuse TdT-positivity presenting a diagnostic challenge as these features could point to a differential diagnosis of diffuse large B-cell lymphoma and/or lymphoblastic lymphoma/leukaemia.

Transformation of a low-grade follicular lymphoma into a composite lymphoma combining a high-grade B-cell lymphoma and a lymphoblastic neoplasm expressing Terminal deoxynucleotidyl Transferase: a case report

Background

High-grade B-cell lymphoma with rearrangements of MYC and BCL2 and/or BCL6 is an aggressive mature B-cell neoplasm, whereas B-lymphoblastic lymphoma is immature cell proliferation, with a frequent positivity for terminal deoxynucleotidyl transferase. The transformation of a low-grade follicular lymphoma into a lymphoblastic neoplasm expressing terminal deoxynucleotidyl transferase is a very rare event.

Case presentation

A 55-year-old Caucasian man was followed for a grade 1–2 follicular lymphoma carrying a t(14;18) IGH/BCL2+ and was initially treated with R-CHOP. The follicular lymphoma presented two relapses. In the third relapse, the patient had multiple lymphadenopathy and ascites, which motivated a retroperitoneal biopsy and an ascitic tap. These samples were analyzed by histological, cytological, flow cytometric, cytogenetic, and molecular assessments. The patient died of a multiple organ dysfunction syndrome 2 weeks after his third relapse. The biopsy revealed a diffuse proliferation made up of two types of tumor cells: centroblasts (Bcl-6-positive) and immature cells (terminal deoxynucleotidyl transferase-positive). Flow cytometric analysis confirmed the immature phenotype, with an expression of terminal deoxynucleotidyl transferase, combined with a loss of membrane immunoglobulins. The cytogenetic analysis performed on the ascites revealed a clonal evolution characterized by a t(8;22)(q24;q11) MYC+ translocation not previously detected in follicular lymphoma. Fluorescence in situ hybridization confirmed the double rearrangement of the BCL2 and MYC genes. Polymerase chain reactions and sequencing were used to study the clonal relationship between follicular lymphoma and the secondary tumors. The IGVH gene rearrangement revealed a unique clonal rearrangement involving an IGVH4–59 subset in all three specimens.

Conclusion

These findings suggest a clonal relationship between the two types of lymphoma cells. Furthermore, they support the transformation of an acute follicular lymphoma into a composite lymphoma combining a high-grade B-cell lymphoma and a lymphoblastic neoplasm expressing terminal deoxynucleotidyl transferase. This case report highlights the possible transformation of follicular lymphoma into a highly aggressive and immature proliferation.

Dramatic increase in gene mutational burden after transformation of follicular lymphoma into TdT+ B-lymphoblastic leukemia/lymphoma

Transformation of follicular lymphoma (FL) into B-lymphoblastic leukemia/lymphoma (B-ALL/LBL) is rare and results in greatly increased aggressiveness of clinical course. Here we present extensive molecular analysis of this unusual transformation, including immunoglobulin (Ig) gene rearrangement studies, cytogenetic analysis, and whole-exome sequencing (WES) of the patient's FL, B-ALL/LBL, and normal cells. Although FL showed marked somatic hypermutation (SHM) of the Ig genes, SHM appeared to be even more extensive in B-ALL/LBL. Cytogenetically, at least three translocations were identified in the B-ALL/LBL involving the BCL2, BCL6, and MYC genes; two of these, the BCL6 and BCL2 gene rearrangements, were already seen at the FL stage. WES identified 751 single-nucleotide variants with high allelic burden in the patient's cells, with the vast majority (575) present exclusively at the B-ALL/LBL stage. Of note, a TAF3 gene mutation was shared by normal, FL, and B-ALL/LBL tissue. A KMT2D nonsense mutation was identified in both FL and B-ALL/LBL and therefore may have contributed directly to lymphomagenesis. Mutations in KDM6A, SMARCA4, CBX1, and JMY were specific to the B-ALL/LBL stage, possibly contributing to the B-ALL/LBL transformation. Functionally, these identified mutations may lead to dysregulation of DNA repair, transcription, and cell differentiation. Thus, these genetic changes, together with the identified chromosomal translocations, may have contributed to lymphoma development and progression. Our findings may improve the mechanistic understanding of the FL-B-ALL/LBL transformation and may have therapeutic implications for this aggressive disease.

Molecular Genetics in the Diagnosis and Biology of Lymphoid Neoplasms

OBJECTIVES

The 2017 Workshop of the Society for Hematopathology/European Association for Haematopathology reviewed the role of molecular genetics in the diagnosis and biology of lymphoid neoplasms.

METHODS

The Workshop Panel reviewed 82 cases.

RESULTS

Molecular genetic testing reveals alterations that expand the spectrum of diseases such as DUSP22 rearrangement in ALK-negative anaplastic large cell lymphoma, large B-cell lymphoma with IRF4 rearrangement, MYD88 mutations in B-cell lymphomas, Burkitt-like lymphoma with 11q aberrations, and diagnostic criteria for high-grade B-cell lymphomas. Therapeutic agents and natural tumor progression may be associated with transcriptional reprogramming that lead to transdifferentiation and lineage switch.

CONCLUSIONS

Application of emerging technical advances has revealed the complexity of genetic events in lymphomagenesis, progression, and acquired resistance to therapies. They also contribute to enhanced understanding of the biology of indolent vs aggressive behavior, clonal evolution, tumor progression, and transcriptional reprogramming associated with transdifferentiation events that may occur subsequent to therapy.

High-grade B-cell lymphomas with TdT expression: a diagnostic and classification dilemma

Mature B-cell neoplasms and immature or precursor B-cell neoplasms need to be distinguished because these patients usually require different therapeutic approaches. B-cell neoplasms that express TdT without unequivocal other features of immaturity may therefore present a diagnostic challenge. We describe 13 patients with TdT-positive aggressive B-cell lymphoma. The clinicopathologic features of these patients were highly heterogeneous, but for the purpose of this study we grouped these cases as follows: (1) de novo high-grade B-cell lymphoma with MYC, BCL2, and/or BCL6 rearrangements (double-hit or triple-hit lymphoma) with TdT expression. In this group we included two cases of de novo composite lymphoma in which there were components of diffuse large B-cell lymphoma and TdT-positive blastic B-cell lymphoma; (2) TdT-positive aggressive B-cell lymphoma arising in patients who previously had follicular lymphoma; (3) initial relapse of TdT-negative aggressive B-cell lymphoma in patients who previously had follicular lymphoma, followed by relapses in which the neoplasm acquired TdT expression; and (4) mature B-cell lymphomas that acquired TdT expression at relapse. This group included one case of EBV-positive diffuse large B-cell lymphoma and one case of pleomorphic variant mantle cell lymphoma. All patients in this study had an aggressive clinical course and a dismal outcome despite appropriate therapy. Rather than "squeezing" these cases into current World Health Organization classification categories, we suggest the use of a descriptive term such as high-grade B-cell lymphoma with TdT expression. In these tumors, the cytogenetic findings and poor prognosis of this patient subgroup suggest that these neoplasms need to be distinguished from B-lymphoblastic leukemia/lymphoma. Segregation of these neoplasms also may foster additional research on these neoplasms.

IG-MYC + neoplasms with precursor B-cell phenotype are molecularly distinct from Burkitt lymphomas

The WHO Classification of Tumours of Haematopoietic and Lymphoid Tissue notes instances of Burkitt lymphoma/leukemia (BL) with IG-MYC rearrangement displaying a B-cell precursor immunophenotype (termed herein "preBLL"). To characterize the molecular pathogenesis of preBLL, we investigated 13 preBLL cases (including 1 cell line), of which 12 were analyzable using genome, exome, and targeted sequencing, imbalance mapping, and DNA methylation profiling. In 5 patients with reads across the IG-MYC breakpoint junctions, we found evidence that the translocation derived from an aberrant VDJ recombination, as is typical for IG translocations arising in B-cell precursors. Genomic changes like biallelic IGH translocations or VDJ rearrangements combined with translocation into the VDJ region on the second allele, potentially preventing expression of a productive immunoglobulin, were detected in 6 of 13 cases. We did not detect mutations in genes frequently altered in BL, but instead found activating NRAS and/or KRAS mutations in 7 of 12 preBLLs. Gains on 1q, recurrent in BL and preB lymphoblastic leukemia/lymphoma (pB-ALL/LBL), were detected in 7 of 12 preBLLs. DNA methylation profiling showed preBLL to cluster with precursor B cells and pB-ALL/LBL, but apart from BL. We conclude that preBLL genetically and epigenetically resembles pB-ALL/LBL rather than BL. Therefore, we propose that preBLL be considered as a pB-ALL/LBL with recurrent genetic abnormalities.

From genetics to the clinic: a translational perspective on follicular lymphoma

Follicular lymphoma (FL) is the most frequent indolent B cell lymphoma and is still considered to be incurable. In recent years, whole-exome sequencing studies of large cohorts of patients have greatly improved our knowledge of the FL mutational landscape. Moreover, the prolonged evolution of this disease has enabled some insights regarding the early pre-lymphoma lesions as well as the clonal evolution after treatment, allowing an evolutionary perspective on lymphomagenesis. Deciphering the earliest initiating lesions and identifying the molecular alterations leading to disease progression currently represent important goals; accomplishing these could help identify the most relevant targets for precision therapy.

A gene-expression profiling score for prediction of outcome in patients with follicular lymphoma: a retrospective training and validation analysis in three international cohorts

Background

Patients with follicular lymphoma (FL) have heterogeneous outcomes. Predictor models able to distinguish, at diagnosis, patients at high versus low risk of progression are still needed.

Methods

The primary objective of this study was to use gene-expression profiling data to build a signature predictive of outcome in patients treated in the rituximab era. In a retrospectively assembled training cohort of 134 pretreatment FL patients from the prospective randomized PRIMA trial, we developed an expression-based predictor of progression-free survival (PFS) that was further evaluated in FFPE samples obtained from three independent international cohorts, using NanoString technology. The validation cohorts comprised a distinct set of patients from the PRIMA trial (n=178), a cohort from the University of Iowa/Mayo Clinic Lymphoma SPORE (n=201) and the Hospital Clinic University of Barcelona (n=109). All tissue samples consisted of pretreatment diagnostic biopsies and were confirmed as FL grade 1-3a. The patients were all treated with regimens containing rituximab and chemotherapy, possibly followed by either rituximab maintenance or ibritumomab-tiuxetan consolidation.

Findings

The expression levels of 395 genes were associated with a risk of progression. Twenty-three genes reflecting both B-cell biology and tumor microenvironment were retained to build a predictive model, which identified a population at an increased risk of progression (p<0.0001). In a multivariate Cox model for PFS adjusted on rituximab maintenance treatment and FLIPI-1, this predictor was found to independently predict progression (adjusted hazard ratio (HR) of the high-risk compared to the low-risk group: 3.68; 95%CI: 2.19-6.17). The digital gene expression data met quality criteria for 460/488 (94%) FFPE samples of the validation cohorts. The predictor performances were confirmed in each of the individual validation cohorts (adjusted HR [95%CI] comparing high risk to low risk groups were respectively 2.57 [1.65-4.01], 2.12 [1.32-3.39] and 2.11 [1.01-4.41]). In the combined validation cohort, the median PFS values were 3.1 (95%CI: 2.4-2.8) and 10.8 (95%CI: 10.1-NR) years in the high- and low-risk groups, respectively. The risk of lymphoma progression at 2 years was twice as high in the high-risk group (38% (95%CI: 29-46) versus 19% (95%CI: 15-24)). In a multivariate analysis, the score predicted PFS independently of anti-CD20 maintenance treatment and of the FLIPI score (hazard ratio for the combined cohort, 2.30; 95%CI, 1.72-3.07).

Interpretation

We developed a robust 23-gene expression-based predictor of PFS, applicable to routinely available FFPE biopsies from FL patients at diagnosis. This score may allow individualizing therapy for patients with FL according to the patient risk category.

Funding

Roche Company, SIRIC Lyric, LYSARC, NIH and the Henry J. Predolin Foundation, Spanish Plan Nacional de Investigacion SAF2015-64885-R.