Clinicopathological and genomic analysis of double-hit follicular lymphoma: comparison with high-grade B-cell lymphoma with MYC and BCL2 and/or BCL6 rearrangements

How I diagnose high-grade B-cell lymphoma

OBJECTIVES

High-grade B-cell lymphoma (HGBL), introduced in the 2016 World Health Organization (WHO) revised fourth edition classification, included cases defined by MYC and BCL2 and/or BCL6 rearrangements or by high-grade morphology. Diagnostic criteria and nomenclature for these lymphomas were refined in the 2022 WHO fifth edition (WHO-5) classification and International Consensus Classification (ICC). This review describes our approach to the diagnosis of HGBL.

METHODS

Two cases are presented illustrating how we diagnose HGBL, including 1 case harboring MYC and BCL6 rearrangements and a second showing TdT expression in an HGBL with MYC and BCL2 rearrangements. The ways in which these cases are distinguished from other lymphomas with high-grade features and the appropriate nomenclature using WHO-5 and ICC classifications are emphasized.

RESULTS

An HGBL diagnosis requires integration of morphology, immunophenotype, and genetics and exclusion of other lymphomas with high-grade morphology, including Burkitt lymphoma, B-lymphoblastic leukemia/lymphoma (B-LBL/ALL), and blastoid mantle cell lymphoma. A diagnosis of HGBL/large B-cell lymphoma with 11q aberration should also be considered in certain patient populations.

CONCLUSIONS

High-grade B-cell lymphomas are subclassified based on morphologic and genetic features. There are differences in the nomenclature and definition of these lymphomas in the WHO-5 and ICC classifications. Distinguishing HGBLs from other mature B-cell lymphomas and B-LBL/ALL is critical so that patients receive appropriate treatment.

Impact of splenectomy on prognosis in lymphoma with splenic involvement

BACKGROUND

Lymphoma presenting splenic invasion as the primary manifestation poses unique diagnostic and therapeutic challenges. This study aims to systematically analyze the clinical features, prognostic factors, and outcomes of patients with splenic involvement as the initial presentation of lymphoma.

METHODS

A retrospective analysis was conducted on lymphoma patients diagnosed with splenic involvement confirmed by histopathological examination at our hospital from March 2011 to February 2023. A total of 113 patients were included based on predefined inclusion and exclusion criteria. The collected data encompassed clinical presentations, diagnostic methods, histopathological features, treatment regimens, and outcomes. Kaplan-Meier survival analysis was performed to generate survival curves for overall survival (OS) and progression-free survival (PFS), with statistical significance assessed using the log-rank test. Additionally, univariate and multivariate analyses utilizing Cox regression analyses were conducted to identify potential prognostic factors.

RESULTS

According to the pathological results, there were 6 types of lymphoma: indolent lymphoma (n = 23.18 of splenic marginal zone lymphoma (SMZL), 4 of follicular lymphoma (FL), 1 of chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL). Aggressive lymphoma (n = 90.74 of diffuse large B cell lymphoma (DLBCL), 10 of NK/T cell lymphoma, 4 of mantle cell lymphoma (MCL), 1 of T lymphoblastic lymphoma, 1 of EBV-positive T cell lymphoma). Diagnosis was confirmed by hollow needle biopsy in 42 patients and through diagnostic splenectomy in 71 patients. 12 patients underwent splenectomy alone while 59 received chemotherapy following splenectomy. The median follow-up time was 37.53 months (range 0 to 162.33 months). The overall 5 year survival (OS) rate for the entire cohort was 62.39% and the 5 year progression-free survival (PFS) rate was 53.98%. Among those who underwent splenectomy, the 5 year OS rate and 5 year PFS rate were 68.06 and 62.50%, which were superior to 52.44 and 37.80% for non-splenectomy patients (P = 0.009 and P < 0.001, respectively). These differences were also observed in the aggressive lymphoma subgroup (n = 90), the 5 year OS rate and 5 year PFS rate were 62.96 and 57.41%, which were also superior to 48.61 and 37.50% for non-splenectomy patients (P = 0.042 and P = 0.017, respectively). In the whole group (n = 110), multivariate model shows prolonged APTT (P = 0.024), virous treatments (P = 0.016) and elevated ferritin (P = 0.017) were independent predicted OS parameters. In aggressive lymphoma subtype (n = 87), treatment (P = 0.021) and prolonged APTT (P = 0.016) emerged as independent risk factors. In indolent lymphomas, no significant differences were found.

CONCLUSION

In this group of lymphoma patients presenting with splenic invasion as the first manifestation, the pathological type was almost aggressive lymphoma, with DLBCL being the main subtype. Common clinical symptoms include elevated ferritin, prolonged APTT and high LDH levels. This study suggests that splenectomy should be considered for these patients when their overall condition allows for safe intervention. Splenectomy combined with chemotherapy can significantly improve the survival time of patients.

High-grade B-cell lymphomas: Double hit and non-double hit

The classification of high-grade B-cell lymphoma (HGBL) has continuously evolved over past decades. These neoplasms, as currently defined, represent about 2% of all non-Hodgkin lymphomas and patients with these neoplasms are often refractory or relapsed following standard therapy. The 5th edition of the World Health Organization classification of hematologic neoplasms (WHO-HAEM5) has refined the classification of HGBL and recognizes two types: (1) Diffuse large B-cell lymphoma (DLBCL)/HGBL with MYC and BCL2 rearrangements, with or without BCL6 rearrangements; and (2) HGBL, not otherwise specified (HGBL-NOS). WHO-HAEM5 excluded DLBCL/HGBL with concurrent MYC and BCL6 rearrangements from this category and reclassified them into DLBCL or HGBL-NOS categories respectively based on morphology. The International Consensus Classification (ICC) takes a slightly different approach. In addition to recognizing the two WHO-HAEM5 categories, they recognize HGBL with concurrent MYC and BCL6 rearrangements as a provisional entity. In this review, we provide an update of HGBL and its subgroups, focusing on their clinicopathologic features, diagnosis, molecular genetic features, and pathogenesis. Our diagnostic approach and caveats for differential diagnosis are also discussed with an emphasis on the differential diagnosis with B lymphoblastic leukemia/lymphoma.

Follicular Lymphoma Detected in a Patient Undergoing Mohs Surgery: A Case Report

Mohs surgery is performed by surgeons trained in detecting specific cutaneous malignancies, including basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and dermatofibrosarcoma protuberans (DFSP). Mohs-trained surgeons are typically not holistic pathologists and may, when working in isolation, fail to identify lesions that are not of cutaneous origin. The presence of a second lesion adjacent to the primary lesion is always a possibility. Such a lesion may be misinterpreted as an extension of the identified primary lesion, leading to unnecessary surgery, or it may be overlooked, resulting in a diagnostic failure. There is an advantage to conducting Mohs surgery with the surgeon and histopathologist reviewing the frozen section slides together, as this approach can aid in the identification of rarer diagnoses. Here, we describe the case of a female patient who underwent Mohs micrographic surgery (MMS) for a recurrent BCC located in the left preauricular area and medial helical rim of the pinna. The surgery involved two excisional stages. The first stage showed morphoeic BCC at all levels of all blocks. The second stage showed no BCC but revealed a dense inflammatory infiltrate. On further assessment by the consultant histopathologist, this infiltrate raised suspicion of possible lymphoma. Based on this consensus, no further Mohs excisional surgery was performed, and the surgical defect was closed. Formalin-fixed paraffin-embedded (FFPE) histological assessment and immunohistochemistry confirmed the diagnosis of cutaneous B-cell follicular lymphoma (FL). Thus, the incidental finding on the examination of fresh frozen MMS sections was correctly interpreted by the combined approach of the Mohs surgeon and pathologist, guiding appropriate and timely management for the patient.

Unraveling the complexity of follicular lymphoma: insights and innovations

This review discusses multiple aspects of follicular lymphoma (FL), including etiology, treatment challenges, and future perspectives. First, we delve into the etiology of FL, which involves a variety of pathogenic mechanisms such as gene mutations, chromosomal abnormalities, immune escape, immune system dysregulation, familial inheritance, and environmental factors. These mechanisms provide the context for understanding the diversity and complexity of FL. Second, we discuss the challenges faced when treating FL, particularly treatment resistance. Therapeutic resistance is a common problem in treatment, but by delving into the mechanisms of resistance, scientists have looked for strategies to combat it, including developing new drugs, improving treatments, and exploring combination therapy strategies. We also emphasize the breakthroughs in molecular biology, especially the study of targeting the BCL2 gene, which provides a new direction for targeted therapy in FL. Immunotherapy, small molecule targeted drugs, and individualized treatment strategies are also promising for the future treatment of FL. Finally, we look to the future, including research on therapeutic resistance, in-depth studies of genetics and gene expression, applications of gene editing and precision medicine, and clinical trials of new treatments. These lines of research offer additional opportunities for treating FL, and despite the challenges, the future is promising. This literature review provides comprehensive and integrated information for the in-depth understanding of FL and relevant treatment approaches.

Mature B, T and NK-cell, plasma cell and histiocytic/dendritic cell neoplasms: classification according to the World Health Organization and International Consensus Classification

In 2022, two updated classification systems for lymphoid neoplasms were published by the World Health Organization (WHO Classification of Haematolymphoid Tumours, 5th edition, referred to hereafter as WHO-HAEM5) and the International Consensus Conference (ICC) (Alaggio et al. in Leukemia 36(7):1720-1748, 2022; Campo et al. in Blood 140(11):1229-1253, 2022). Both classifications were conceived by both pathologists and clinicians with expertise in the field. The reasons for this have been reviewed previously (Arber et al. in Virchows Arch 482(1):1-9, 2023; Cree in Leukemia 36(7):1701-1702, 2022, Leukemia 36(11):2750, 2022). Given that both groups were using data-driven processes and consensus and used the revised 4th edition of the WHO Classification of Haematolymphoid Tumours (WHO-HAEM4R) as a starting point, it is not entirely surprising that the resulting classifications are quite similar. However, they are not identical and reflect preferences or approaches for certain unsettled areas as well as preferred terminology. In this review, we will compare nomenclature of the WHO-HAEM5 and ICC classifications, focusing on lymphoid neoplasms and lymphoproliferative disorders (LPDs).

Oral follicular lymphoma: a clinicopathologic and molecular study

Follicular lymphoma is a hematolymphoid neoplasm that originates from germinal center B cells. It is made up of a combination of small cleaved centrocytes and a varying quantity of larger non-cleaved centroblasts to describe the clinical, microscopic, immunohistochemical, and molecular features of oral follicular lymphomas. Follicular lymphomas affecting the oral cavity were retrieved from pathology files. Immunohistochemistry was performed to confirm the diagnosis, and fluorescence in situ hybridization (FISH) was employed to detect rearrangements in BCL2, BCL6, and MYC genes. Clinical and follow-up data were obtained from the patient's medical and pathology files. Twenty cases were obtained. There was an equal sex distribution (10 males: 10 females) and a mean age of 60.9 years (range: 10-83 years-old). Lesions presented as asymptomatic swellings, usually in the palate (10 cases) and the buccal mucosa (7 cases). Five patients presented with concomitant nodal involvement. Microscopic evaluation depicted the follicular growth pattern with diffuse areas in six cases. Grades 1 and 2 follicular lymphomas represented 12 cases, while grade 3A neoplasms accounted for other 8 cases. Two cases showed rearrangements in MYC, BCL2, and BCL6 genes, while single BCL2 translocation was found in eight cases. Two cases had no translocation. Three patients deceased and the 2-year overall survival achieved 88%. Follicular lymphoma affecting the oral cavity is uncommon, usually affects the palate as a non-ulcerated swelling and the presence of a systemic disease most always be ruled out.

Measurable Residual Disease Monitoring in Lymphoma

PURPOSE OF REVIEW

The utility of analyzing circulating tumor DNA (ctDNA), circulating tumor cells (CTCs), and disease in the bone marrow as an adjunctive tool in caring for hematologic cancer patients is expanding. This holds true for lymphoma where these biomarkers are being explored as a means of genotyping and quantifying disease. Regarding the latter, they can be used to monitor measurable residual disease (MRD) during and after treatment. This holds potential for aiding clinical decisions amidst treatment, detecting earlier relapse, and improving prognostication. Here, we review the evidence to support these applications in a variety of lymphoma subtypes.

RECENT FINDINGS

Numerous clinical trials across a variety of lymphomas have demonstrated value in MRD monitoring. MRD monitoring is often prognostic for progression free survival (PFS) and even overall survival (OS) at several time points in a disease course, particularly when utilizing serial measurements. With regards to tailoring treatment, there are a growing number of trials examining MRD-adaptive treatment strategies to intensify or de-escalate treatment to individualize care. Lastly, MRD monitoring has been utilized successfully in detecting earlier relapse when compared to more standard methods of clinical surveillance such as radiographic assessment. Although not routinely implemented into clinical practice, MRD monitoring in lymphoma is helping shape the future landscape of this disease by aiding in prognostication, guiding therapy, and detecting earlier relapse. Steps to standardize and further examine this technology prospectively are being taken to bring MRD monitoring to the forefront of the field.

Prognostic evaluation of system immune-inflammatory index and prognostic nutritional index in double expressor diffuse large B-cell lymphoma

Predicting MYC and BCL2 double-expressor lymphoma prognosis using the system immune-inflammatory index (SII) and prognostic nutritional index (PNI) (DEL). From January 2015 to December 2021, 281 diffuse large B-cell lymphoma (DLBCL) wax blocks were used to make tissue chips. Screening double expressor lymphoma (DEL) instances involved immunocytochemistry and fluorescence in situ hybridization. Academic analysis used clinicopathological characteristics and follow-up data. SII, PNI, and DEL prognosis were correlated using univariate and multivariate cox regression analysis. The median age of 78 DEL patients is 60 (range: 43-74). SII and PNI cut-off values of 603.5, 3.07, and 144 predict PFS and OS well. Lower SII is associated with longer PFS (HR for SII = 0.34, 95% CI 0.15-0.76, P = 0.006; HR for NLR = 0.46, 95% CI 0.22-0.99, P = 0.048; HR for PLR = 0.39, 95% CI 0.17-0.94, P = 0.025; LMR = 0.39, 95%, CI 0.17-0.94, P = 0.025) and OS (HR for SII = 0.16, 95% CI 0.05-0.51, P = 0.005; HR for PNI = 0.20, 95% CI 0.06-0.62, P = 0.002). SII and PNI are promising predictors for twofold expressor DLBCL. Combining these increase prediction accuracy.

The pathobiology of follicular lymphoma

Follicular lymphoma is one of the most frequent lymphomas. Histologically, it is characterized by a follicular (nodular) growth pattern of centrocytes and centroblasts; mixed with variable immune microenvironment cells. Clinically, it is characterized by diffuse lymphadenopathy, bone marrow involvement, and splenomegaly. It is biologically and clinically heterogeneous. In most patients it is indolent, but others have a more aggressive evolution with relapses; and transformation to diffuse large B-cell lymphoma. Tumorigenesis includes an asymptomatic preclinical phase in which premalignant B-lymphocytes with the t(14;18) chromosomal translocation acquire additional genetic alterations in the germinal centers, and clonal evolution occurs, although not all the cells progress to the tumor stage. This manuscript reviews the pathobiology and clinicopathological characteristics of follicular lymphoma. It includes a description of the physiology of the germinal center, the genetic alterations of BCL2 and BCL6, the mutational profile, the immune checkpoint, precision medicine, and highlights in the lymphoma classification. In addition, a comment and review on artificial intelligence and machine (deep) learning are made.

Follicular lymphoma and marginal zone lymphoma: how many diseases?

Follicular lymphoma (FL) and marginal zone lymphoma (MZL) are indolent mature B-cell neoplasms with variable clinical presentation and distinct histopathologic features. Recent advances in the biology and molecular characteristics of these lymphomas have further expanded our understanding of the heterogeneous nature of these lymphomas, with increasing recognition of specific disease entities within the broader categories of FL and MZL. Here, we discuss the conclusions of the 2022 International Consensus Classification of Mature Lymphoid Neoplasms (2022 ICC) dealing with FL, and review differences with the proposed WHO 5th Edition classification. We review issues related to grading and alternative forms of FL especially those lacking the genetic hallmark of FL, the t(14;18) chromosomal alteration. Among them, t(14;18)-negative CD23⁺ follicle center lymphoma has been proposed by the 2022 ICC as a provisional entity. Other follicle center-derived lymphomas such as pediatric-type follicular lymphoma, testicular follicular lymphoma, primary cutaneous follicle center lymphoma, and large B-cell lymphoma with IRF4 rearrangement are considered distinct entities separate from conventional FL. Importantly, large B-cell lymphoma with IRF4 rearrangement introduced as a provisional entity in the WHO 2017 is upgraded to a definite entity in the 2022 ICC. We also discuss diagnostic strategies for recognition of MZLs including splenic MZL, extranodal MZL (MALT lymphoma), and primary nodal MZL. The importance of molecular studies in the distinction among marginal zone lymphoma subtypes is emphasized, as well as their value in the differential diagnosis with other B-cell lymphomas.

Diagnostic approaches and future directions in Burkitt lymphoma and high-grade B-cell lymphoma

Since the 2016 WHO update, progress has been made in understanding the biology of Burkitt lymphoma (BL) and the concept of high-grade B-cell lymphomas (HGBCL) that allows some degree of refinement. The summary presented here reviews in detail the discussions of the Clinical Advisory Committee and expands upon the newly published 2022 International Consensus Classification for lymphoid malignancies (Campo et al. Blood, 2022). BL remains the prototypic HGBCL and diagnostic criteria are largely unchanged. HGBCL with MYC and BCL2 and HGBCL with MYC and BCL6 rearrangements are now separated to reflect biologic and pathologic differences. HGBCL, NOS remains a diagnosis of exclusion that should be used only in rare cases. FISH strategies for diffuse large B-cell lymphoma (DLBCL) and HGBCL are discussed in detail for these diseases. Advances in integrative analysis of mutations, structural abnormalities, copy number, and gene expression signatures allow a more nuanced view of the heterogeneity of DLBCL, NOS as well as definitions of HGBCL and point to where the future may be headed for classification of these diseases.

MYC/BCL2 double- and MYC/BCL2/BCL6 triple-hit follicular lymphomas associated with t(8;14;18)(q24;q32;q21)

We describe two follicular lymphoma (FL) patients with MYC/BCL2 double- and MYC/BCL2/BCL6 triple-hit translocations. The first patient (case 1) was a man in his 30s who presented with stage IV disease with leukemic manifestation. The second patient (case 2) was a man in his 60s who presented with relapsed FL, but his disease was in a limited stage. Histopathology of the lymph node biopsies revealed grade 3A FL in both cases. MYC positivity and the Ki-67-labeling index were 60-70 and 20% in case 1 and 30 and 50% in case 2, respectively. G-banding revealed t(8;14;18)(q24;q32;q21) in both cases and fluorescence in situ hybridization using MYC, IGH, and BCL2 break-apart probes confirmed t(8;14;18)(+5'BCL2,-3'MYC;+3'MYC,-5'IGH;+5'IGH,-5'BCL2). In case 2, additional materials of der(8)t(8;14;18) were duplicated and translocated to chromosome Y, and t(3;16)(q27;p13)/BCL6::CIITA was identified. We obtained BCL2-major breakpoint region::IGHJ5::IGHG1 and MYC exon 2::IGHA2 fusion sequences by long-distance polymerase chain reaction in case 1, and proposed that t(8;14;18) was generated by two-step translocations and that BCL2::IGH and MYC::IGH involved the same IGH allele. Both patients responded to the standard chemotherapy for FL. We suggest that the presence of t(8;14;18) in FL does not immediately indicate high-grade transformation and aggressive clinical behavior requiring intensive chemotherapy.

Copy Number Alteration and Mutational Profile of High-Grade B-Cell Lymphoma with MYC and BCL2 and/or BCL6 Rearrangements, Diffuse Large B-Cell Lymphoma with MYC-Rearrangement, and Diffuse Large B-Cell Lymphoma with MYC-Cluster Amplification

Diffuse large B-cell lymphoma (DLBCL) with MYC alteration is classified as high-grade B-cell lymphoma with MYC and BCL2 and/or BCL6 rearrangements (double/triple-hit lymphoma; DHL/THL), DLBCL with MYC rearrangement (single-hit lymphoma; SHL) and DLBCL with MYC-cluster amplification (MCAD). To elucidate the genetic features of DHL/THL, SHL, and MCAD, 23 lymphoma cases from Tokai University Hospital were analyzed. The series included 10 cases of DHL/THL, 10 cases of SHL and 3 cases of MCAD. The analysis used whole-genome copy number microarray analysis (OncoScan) and a custom-made next-generation sequencing (NGS) panel of 115 genes associated with aggressive B-cell lymphomas. The copy number alteration (CNA) profiles were similar between DHL/THL and SHL. MCAD had fewer CNAs than those of DHL/THL and SHL, except for +8q24. The NGS profile characterized DHL/THL with a higher "mutation burden" than SHL (17 vs. 10, p = 0.010), and the most relevant genes for DHL/THL were BCL2 and SOCS1, and for SHL was DTX1. MCAD was characterized by mutations of DDX3X, TCF3, HLA-A, and TP53, whereas MYC was unmutated. In conclusion, DHL/THL, SHL, and MCAD have different profiles.

The multilobated morphology is still a better prognosis factor of diffuse large B-cell lymphoma in the R-CHOP era

Diffuse large B-cell lymphoma (DLBCL) is the most common type of B-cell lymphoma. Although the multilobated subtype of DLBCL has been observed since the 1970s, little is known about the clinical significance of this unique variant in the era of rituximab, cyclophosphamide, hydroxydaunorubicin, oncovin, prednisone/prednisolone (R-CHOP) therapy. In this study, the retrospective clinicopathological analysis of 312 patients diagnosed with DLBCL showed that the multilobated DLBCL group comprised 11% of the cases and was predominantly male (p = 0.027), achieved complete remission in the first therapy (p = 0.023), and exhibited germinal center B-cell phenotypes in the Hans algorithm (p = 0.025). The multilobated DLBCL groups had a better prognosis in overall survival (OS) and progression-free survival (PFS) than the non-multilobated DLBCL group (OS, p = 0.006; PFS, p = 0.010). In the multivariate Cox regression analyses for OS, independent prognosis factors were high soluble IL-2 receptor (p = 0.025), high risk of International Prognostic Index, and multilobated morphology (p = 0.031). The most characteristic copy number gains found in more than 50% of the cases were located at 1q, 3p, 10q, 12q, and 14q. Overall, the multilobated morphology in DLBCL exhibits a good outcome in the R-CHOP era.

B Lymphoproliferative Neoplasms of Uncertain Biological Significance: Report from the IV Workshop of the Italian Group of Hematopathology and Review of the Literature

Lymphoproliferative neoplasms of uncertain biological significance are increasingly encountered due to widespread usage of immunophenotypic and molecular techniques. Considering that clearer biological criteria and patient management have been established for B-cell lymphoproliferative diseases of undetermined significance occurring in the peripheral blood, many issues are still obscure for early lesions detected in lymphoid tissues. Regardless that some categories of lymphoproliferative neoplasms of uncertain biological significance have been recognized by the 4th edition of the WHO, other anecdotal early lymphoproliferative lesions still remain fully undefined. Some early lesions frequently originate from the germinal center, including atypical germinal centers BCL2-negative, an early pattern of large B-cell lymphoma with IRF4 rearrangement, and “in situ” high-grade B lymphomas. Moreover, other early lymphoproliferative lesions arise outside the germinal center and include those developing within the setting of monocytoid B-cell hyperplasia, but they also can be directly or indirectly associated with chronic inflammations. This review aims to summarize the concepts discussed during the IV Workshop organized by the Italian Group of Hematopathology, focus on the state-of-the-art on B-cell lymphoproliferative neoplasms of uncertain biological significance, and offer operative insights to pathologists and clinicians in routine diagnostics.

The International Consensus Classification of Mature Lymphoid Neoplasms: a report from the Clinical Advisory Committee

Since the publication of the Revised European-American Classification of Lymphoid Neoplasms in 1994, subsequent updates of the classification of lymphoid neoplasms have been generated through iterative international efforts to achieve broad consensus among hematopathologists, geneticists, molecular scientists, and clinicians. Significant progress has recently been made in the characterization of malignancies of the immune system, with many new insights provided by genomic studies. They have led to this proposal. We have followed the same process that was successfully used for the third and fourth editions of the World Health Organization Classification of Hematologic Neoplasms. The definition, recommended studies, and criteria for the diagnosis of many entities have been extensively refined. Some categories considered provisional have now been upgraded to definite entities. Terminology for some diseases has been revised to adapt nomenclature to the current knowledge of their biology, but these modifications have been restricted to well-justified situations. Major findings from recent genomic studies have impacted the conceptual framework and diagnostic criteria for many disease entities. These changes will have an impact on optimal clinical management. The conclusions of this work are summarized in this report as the proposed International Consensus Classification of mature lymphoid, histiocytic, and dendritic cell tumors.

Unusual presentation of extra-nodal double-hit follicular lymphoma: a case report

Background

To the best of our knowledge, this case represents the first report of an extranodal double-hit follicular lymphoma (DH-FL) as an intestinal polypoid lesion.

Case presentation

A 72-year-old woman presents with constipation. Colonoscopy reveals a sessile polypoid lesion of the colon bearing morphological, immunohistochemical and molecular hallmarks of DH-FL. Complete clinical staging and bone marrow biopsy showed no signs of disseminated disease. The patient, after two years of follow-up is still free of disease confirming the indolent behaviour of this limited lesion.

Conclusions

A synoptic view at all the features of the patient and not merely at the molecular hallmarks of a disease are essential to establish the correct clinical approach.

Clinicopathological analysis of follicular lymphoma with BCL2, BCL6, and MYC rearrangements

Most follicular lymphomas (FL) show t(14;18)/IGH-BCL2 translocation, but rearrangement (R) negative cases exist. A series of 140 FL patients with a BCL2, BCL6, and MYC gene status examined by fluorescence in situ hybridization (FISH) were classified into five groups: (a) BCL2-R group (BCL2-R/BCL6-G/MYC-G) (G, germline), 77 cases; (b) BCL2/BCL6 double-R group (BCL2-R/BCL6-R/MYC-G), 16 cases; (c) BCL6-R group (BCL2-G/BCL6-R/MYC-G), 16 cases; (d) MYC-R group (BCL2-R or G/BCL6-R or G/MYC-R), three cases; (e) Triple-G group (BCL2-G/BCL6-G/MYC-G), 28 cases. The BCL6-R group had different clinicopathological characteristics. It showed lower rates of an advanced clinical stage and bone marrow invasion, less disease progression (p = 0.036), and a 'trend' toward a favorable progression-free survival (PFS) (p = 0.06). It also showed higher rates of grade 3A and MUM1-expression, and when analyzing the interfollicular spread pattern of CD20-positive cells, had fewer cases showing the IF3+ pattern (high interfollicular spread). Moreover, cases with BCL6-R and/or BCL6 gain (with cases of BCL2 rearrangement and/or of copy number gain excluded) correlated with favorable PFS (p = 0.014) and less IF3+ pattern (p = 0.007). We demonstrated that BCL6-R FLs showed unique clinicopathological findings, and FISH of BCL2, BCL6, and MYC is useful for FL diagnosis and clinical management.

Mitochondria and Their Relationship with Common Genetic Abnormalities in Hematologic Malignancies

Hematologic malignancies are known to be associated with numerous cytogenetic and molecular genetic changes. In addition to morphology, immunophenotype, cytochemistry and clinical characteristics, these genetic alterations are typically required to diagnose myeloid, lymphoid, and plasma cell neoplasms. According to the current World Health Organization (WHO) Classification of Tumors of Hematopoietic and Lymphoid Tissues, numerous genetic changes are highlighted, often defining a distinct subtype of a disease, or providing prognostic information. This review highlights how these molecular changes can alter mitochondrial bioenergetics, cell death pathways, mitochondrial dynamics and potentially be related to mitochondrial genetic changes. A better understanding of these processes emphasizes potential novel therapies.

AID is a poor prognostic marker of high-grade B-cell lymphoma with MYC and BCL2 and/or BCL6 rearrangements

Diffuse large B-cell lymphoma with MYC rearrangement is defined as double/triple-hit lymphoma (DHL/THL) or single-hit lymphoma (SHL) by the inclusion of the BCL2 and BCL6 rearrangements status. DHL/THL is called as "high-grade B-cell lymphoma with MYC and BCL2 and/or BCL6 rearrangements" in the World Health Organization 2017 Classification of Tumors of Hematopoietic and Lymphoid Tissues. To find a prognostic biomarker of DHL/THL, we firstly examined 19 cases (molecular analysis series;10 cases of DHL/THL and 9 cases of SHL) with gene expression profile analysis. The gene expression profile analysis showed that the high expression of AICDA was associated with an adverse prognosis in DHL/THL, but not in SHL. Then, we evaluated immunohistochemical expression of AID, the protein product of AICDA, in 50 cases (molecular analysis series of 19 cases and additional immunohistochemistry series of 31 cases; 12 cases of DHL/THL and 19 cases of SHL) and confirmed that its expression was also associated with an adverse prognosis in DHL/THL. Therefore, AICDA and AID can be a predictor of an adverse clinical outcome in DHL/THL and immunohistochemistry of AID is useful to find DHL/THL-adverse prognosis group.

Upward trend in follicular lymphoma among the Korean population: 10-year experience at a large tertiary institution

Background

Follicular lymphoma (FL) is the second most common non-Hodgkin lymphoma (NHL) in Western countries. However, it is relatively rare in Asia. This study examined epidemiologic characteristics of FL in South Korea, with an emphasis on recent trends of increase in cases.

Methods

We retrospectively examined 239 cases of newly diagnosed FL at a large tertiary institution in Korea (Asan Medical Center, Seoul, Republic of Korea) between 2008 and 2017. Age-adjusted incidence rates and clinicopathological variables were analyzed, and joinpoint regression analysis was used to identify the changes.

Results

The age-adjusted incidence of FL significantly increased during the study period (p = .034), and the ratio of (relative incidence) patients with FL to patients with NHL increased from 4.28% to 9.35% in the same period. Over the 10-year study assessment duration, the proportion of patients with stage III/IV FL (p = .035) and expression of BCL2 (p = .022) or BCL6 (p = .039) significantly increased. From 2013–2017, the proportion of patients with highrisk Follicular Lymphoma International Prognostic Index (FLIPI) score increased (21.5% to 28.7%), whereas that of low-risk FLIPI decreased (55.4% to 38.6%), although those results were not statistically significant (p = .066).

Conclusions

We found an increasing incidence of FL, with a disproportionate increase in the incidence of high-stage disease and recent changes in the clinicopathologic features of the Korean patient population.

High-grade Follicular Lymphomas Exhibit Clinicopathologic, Cytogenetic, and Molecular Diversity Extending Beyond Grades 3A and 3B

Although follicular lymphoma (FL) is usually graded as FL1-2, FL3A, and FL3B, some borderline cases can be observed and led us to investigate the clinicopathologic diversity of grade 3 FL (FL3). Among 2449 FL patients enrolled in Lymphoma Study Association (LYSA) trials, 1921 cases with sufficient material underwent a central pathologic review. The resulting diagnoses comprised 89.6% FL1-2 (n=1723), 7.2% FL3A (n=138), and 0.5% purely follicular FL3B (n=9). The remaining 51 unclassifiable cases (2.7%) exhibited high-grade features but did not meet WHO criteria for either FL3A or FL3B; and were considered as "unconventional" high-grade FL (FL3U). FL3U morphological pattern consisted of nodular proliferation of large cleaved cells or small-sized to medium-sized blast cells. Compared with FL3A, FL3U exhibited higher MUM1 and Ki67 expression, less BCL2 breaks and more BCL6 rearrangements, together with a higher number of cases without any BCL2, BCL6 or MYC rearrangement. FL3U harbored less frequent mutations in BCL2, KMT2D, KMT2B, and CREBBP than FL3A. MYC and BCL2 were less frequently mutated in FL3U than FL3B. Rituximab cyclophosphamide, doxorubicin, vincristine, and prednisone treated FL3U patients had a worse survival than FL1-2 patients with similar follicular lymphoma international prognostic index and treatment. These results suggest that high-grade FLs encompass a heterogeneous spectrum of tumors with variable morphology and genomic alterations, including FL3U cases that do not strictly fit WHO criteria for either FL3A or FL3B, and display a worse outcome than FL1-2. The distinction of FL3U may be useful to allow a better comprehension of high-grade FLs and to design clinical trials.

Adverse outcome in follicular lymphoma is associated with MYC rearrangements but not MYC extra copies

Follicular lymphomas (FLs) with MYC rearrangements (MYC-R) and extra copies of MYC (MYC-EC) are rare and the prognosis impact is uncertain. We conducted a retrospective study including 321 FL patients, among whom 259 (81%) had no 8q24 alterations and 62 (19%) were assigned to 8qAlt. Forty-five cases were classified as MYC-EC and six as MYC-R. MYC-R patients were significantly older (P = 0·008), had higher follicular lymphoma international prognostic index (FLIPI) stage (P = 0·05) and β2-microglobulin (β2m; P = 0·05). Among patients treated with immuno-chemotherapy, four presented a MYC-R and 25 a MYC-EC. Univariate analysis showed the absence of significant difference between MYC-EC and normal MYC (MYC-NL) regarding progression-free survival (PFS; HR1·3; 95% CI [0·4-1·6]) and specific overall survival (SOS; HR 1·6; 95% CI [0·4-5·7]). Those results were compared to data from the PRIMA trial. This confirmed that MYC-EC had no impact on PFS (P = 0·86) or SOS (P = 0·9). Conversely, MYC-R was associated with a trend to inferior outcome regarding PFS (HR : 6·1; 95% CI [2·2-17·1]; P = 0·00026), lymphoma-related death (SOS; HR 13·6; 95% CI [2·9-65]; P = 0·00014) and risk of transformation (transformation-free survival (TFS); HR 82·7; 95% CI [14·8-463·4]; P < 0·0001). In conclusion, MYC-EC has no prognostic impact in FL but MYC-R FL tended to be associated with an increased risk of transformation and poorer outcome.

Case Report: Concurrent Occurrence of Abdominal Double Expressor Lymphoma and Jejunum Follicular Lymphoma

Double expressor lymphoma (DEL), defined as overexpression of BCL2 and MYC, is an aggressive subtype of diffuse large B cell lymphoma (DLBCL). Here we report a case of a 64-year-old female diagnosed with abdominal DEL transformed from jejunum follicular lymphoma (FL). 18F-fluorodeoxyglucose (FDG)-positron emission tomography showed diffuse accumulation of FDG into the peritoneum and small bowel wall. Double balloon-assisted enteroscopy revealed whitish submucosal tumors in the proximal jejunum. Aggregation of atypical lymphocytes positive for CD20, CD79a, and BCL2 was seen in the jejunal biopsy samples. These atypical lymphocytes were monoclonal since cell surface expression of Ig light chains was limited to κ chain by flow-cytometry. Thus, immunohistochemical and flowcytometric analyses data were consistent with FL of the jejunum. Neoplastic lymphocytes obtained from ascites were positive for CD10, CD20, CD79a, BCL2, and BCL6. Fluorescence in situ hybridization (FISH) showed formation of BCL2/IgH fusion gene and extra copies of MYC, the former of which is a characteristic chromosomal abnormality of FL. These genetic alterations and protein expression profiles of ascitic fluid cells were consistent with those of DEL transformed from FL. Given that a significant population of patients with indolent FL of the gastrointestinal tract developed into aggressive DLBCL, it is likely that primary FL of the jejunum transformed into the abdominal aggressive DEL in this case. This case is unique in that concurrent occurrence of FL and DEL was confirmed by immunohistochemical and FISH analyses and that abdominal DEL transformed from jejunal FL was highly suspected.

Relative frequency and clinicopathologic characteristics of MYC-rearranged follicular lymphoma

MYC rearrangement is a relatively rare genetic abnormality in follicular lymphoma (FL). In this study, we evaluated the relative frequency of MYC rearrangement in 522 cases of FL and studied their clinicopathologic, cytogenetic, and molecular characteristics. Fluorescence in situ hybridization studies for MYC (break-apart probe), MYC/IGH, IGH/BCL2, and BCL6 rearrangements were performed on tissue microarrays. Immunohistochemical stains for CD10, BCL2, BCL6, and MYC were performed and scored on MYC-rearranged cases. On 4 FL cases, a custom targeted panel of 356 genes was used for mutation analysis. Ten cases (1.9%) were positive for MYC rearrangement. Histologically, 6 of 10 cases were grade 1-2, and 4 cases were grade 3A. By immunohistochemistry, 9 of 9 tested cases were CD10+, all cases were BCL6+, and 9/10 cases were BCL2+. MYC protein staining was low in all cases tested. IGH/BCL2 rearrangement was detected in 5 of 9 cases, whereas BCL6 rearrangement was detected in 3 of 7 tested cases and 4 of 10 cases showed MYC/IGH rearrangement. The most commonly detected mutations in the MYC-positive cases included HLA-B, TNFRSF14, and KMT2D. MYC and/or B2M abnormalities were detected in 2 cases. In conclusion, MYC rearrangement is uncommon in FL and these cases do not appear to have specific histologic characteristics. Molecular analysis showed abnormalities in genes associated with transformation, namely MYC and B2M. Larger studies are needed to evaluate if MYC-rearrangement in FL has prognostic significance.

Double expressor and double/triple hit status among primary cutaneous diffuse large B-cell lymphoma: a comparison between leg type and not otherwise specified subtypes

Primary cutaneous diffuse large B-cell lymphomas (pcDLBCLs) are rare hematological neoplasms. The pcDLBCL category includes primary cutaneous large B-cell lymphoma leg type (pcDLBCL-LT), characterized by a particularly unfavorable outcome, and primary cutaneous large B-cell lymphoma not otherwise specified (pcDLBCL-NOS), a widely debated subentity with a more indolent course. The negative prognostic impact of double expressor status (DE status, given by coexpression of MYC and BCL2) and double hit/triple hit status (DH/TH status, given by translocations of MYC and BCL2 and/or BCL6) in nodal DLBCL is well known; however, no unanimous conclusions regarding relevance of DE and DH/TH status have been reached in pcDLBCL. Therefore, our purpose has been to investigate the presence and prognostic relevance of DE and DH/TH status among a retrospective multicentric cohort of 16 cases of pcDLBCL-LT and 17 cases of pcDLBCL-NOS. All cases were thoroughly reevaluated, both on a morphological and immunohistochemical level, and tested by means of fluorescence in situ hybridization for MYC, BCL2 and BCL6 rearrangements. DE status was observed in 69% of pcDLBCL-LT cases and in 24% of pcDLBCL-NOS cases; however, it did not impact prognosis in any of the groups examined. Combining molecular results, we highlighted a relevant fraction of DH pcDLBCL cases (three pcDLBCL-LT cases and one pcDLBCL-NOS case) and the very first case of TH pcDLBCL-LT reported to date. All DH cases were characterized by MYC and BCL6 rearrangements. Overall, DH/TH cases represented 15% (5/33) of all pcDLBCLs and were mostly pcDLBCL-LT. DH/TH status and DH status alone were associated with poorer overall survival and disease-specific survival (both p < 0.05) among all pcDLBCLs, without reaching statistical significance in the pcDLBCL-LT and pcDLBCL-NOS groups. In conclusion, MYC, BCL2, and BCL6 cytogenetical testing could be useful in identifying a putative subset of more aggressive pcDLBCLs, although this observation has to be confirmed by further studies.

Double-Hit and Triple-Hit Follicular Lymphoma

OBJECTIVES

To better characterize the clinicopathologic presentation and outcomes of follicular lymphoma with MYC and BCL2 and/or BCL6 rearrangements (double-hit and triple-hit follicular lymphoma), we present three cases from our institution and perform a literature review of 37 published cases.

METHODS

Cases were identified using institutional SoftPath software and the MEDLINE database via the PubMed search engine. Clinical and pathologic data were collected with subsequent stratification by histologic grade and treatment for comparison.

RESULTS

Similar to classic follicular lymphoma, patients presented most often with low-grade (1-2) but high-stage (III-IV) disease with absence of B symptoms; however, overall survival was worse than that of traditional follicular lymphoma. In a small sample size, etoposide, prednisone, vincristine, cyclophosphamide, doxorubicin, and rituximab (EPOCH-R) achieved better outcomes than a regimen of rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP). Specific pathologic features that might prompt testing for MYC rearrangement include elevated proliferation index out of proportion to cytology and aggressive features such as angioinvasion.

CONCLUSIONS

Double-hit and triple-hit follicular lymphoma may be better classified as a distinct entity from classical follicular lymphoma with a worse prognosis. Aggressive therapy with a treatment regimen used for high-grade B-cell lymphoma with MYC and BCL2 and/or BCL6 rearrangements might be beneficial, but more evidence is needed to justify aggressive treatment as standard of care.

Clinical Interest of LMO2 Testing for the Diagnosis of Aggressive Large B-Cell Lymphomas

MYC rearrangements usually confer aggressive biological behavior to large B-cell lymphomas. In this study, we aimed to evaluate the relevance of LMO2 detection to the clinical approach to these tumors. First, the ability of LMO2 loss of expression to recognize the presence of MYC rearrangements was evaluated. A series of 365 samples obtained from 351 patients, including 28 Burkitt lymphoma, 230 diffuse large B-cell lymphoma, 30 high-grade B-cell lymphoma with MYC and BCL2/BCL6 rearrangements, eight high-grade B-cell lymphoma-NOS, 43 transformed diffuse large B-cell lymphoma, and 26 high-grade follicular lymphomas was analyzed. Among the CD10-positive tumors prospectively analyzed in whole tissue sections, LMO2 negative expression obtained values of 88% sensitivity, 94% specificity, and 93% accuracy, proving the utility of LMO2 to screen MYC rearrangements. In addition, survival analyses were performed in a series of 155 patients. As per univariate analyses, the prognosis relevance of LMO2 was as useful as that of the diagnostic categories, MYC rearrangements, and MYC immunohistochemistry. Multivariate models revealed that both LMO2 (hazard ratio 0.51 p = 0.02) and IPI (hazard ratio 1.67 p < 0.005) were independent variables predicting overall survival. Finally, MYC and LMO2 mRNA expression were analyzed in a small group of cases. Taken together, these findings show the interest of LMO2 testing in large B-cell lymphomas.

The broad landscape of follicular lymphoma: Part II

Follicular lymphoma is a neoplasm derived from follicle center B cells, typically both centrocytes and centroblasts, in variable proportions according to the lymphoma grading. The pattern of growth may be entirely follicular, follicular and diffuse and rarely completely diffuse. It represents the second most common non-Hodgkin lymphoma, after diffuse large B-cell lymphoma and it is the most common low-grade mature B-cell lymphoma in Western countries. In the majority of cases, follicular lymphoma is a nodal tumor, occurring in adults and is frequently associated with the translocation t(14;18)(q32;q21)/IGH-BCL2. However, in recent years the spectrum of follicular lymphoma has expanded and small subsets of follicular lymphoma, which differ from common follicular lymphoma, have been identified and included in the current 2017 WHO classification. The aim of our review is to describe the broad spectrum of follicular lymphoma, pointing out that the identification of distinct clinicopathological variants of follicular lymphoma is relevant for the patient outcomes and treatment.

The broad landscape of follicular lymphoma: Part I

Follicular lymphoma is a neoplasm derived from follicle center B cells, typically both centrocytes and centroblasts, in variable proportions according to the lymphoma grading. The pattern of growth may be entirely follicular, follicular and diffuse, and rarely completely diffuse. It represents the second most common non-Hodgkin lymphoma, after diffuse large B-cell lymphoma and is the most common low-grade mature B-cell lymphoma in western countries. In the majority of cases, follicular lymphoma is a nodal tumor, occurring in adults and frequently associated with the translocation t(14;18)(q32;q21)/IGH-BCL2. However, in recent years the spectrum of follicular lymphoma has expanded and small subsets of follicular lymphoma, which differ from common follicular lymphoma, have been identified and included in the current 2017 WHO classification. The aim of our review is to describe the broad spectrum of follicular lymphoma, pointing out that the identification of distinct clinicopathological variants of follicular lymphoma is relevant for patient outcomes and choice of treatment.

Colorectal diffuse large B-cell lymphoma: molecular subclassification and prognostic significance of immunoglobulin gene translocation

Primary colorectal diffuse large B-cell lymphoma (DLBCL) is rare, and its clinicopathological and genetic features are poorly understood. The aim of our study was to elucidate the frequency and prognostic significance of molecular subgroups in colorectal DLBCL. We examined 25 cases of colorectal lymphoma with DLBCL-like morphology and classified them into germinal center B-cell like (GCB)/non-GCB subgroups by immunohistochemistry (IHC) for CD10, bcl-6 and MUM1, or into double-expressor (DE)/non-DE subgroups by IHC for bcl-2 and c-myc. Translocations involving BCL2, BCL6, MYC, IGH, IGK, IGL, and MALT1 were also investigated using break-apart fluorescence in situ hybridization (FISH). The 25 cases were classified into two entities-DLBCL, not otherwise specified (NOS) (n = 23; 92%) and high grade B-cell lymphoma, double hit (n = 2; 8%)-according to the recent WHO classification. None of them showed histological evidence of Epstein-Barr virus infection or high-grade transformation from low grade B-cell lymphoma. Ten cases were GCB-type and four cases were DE-type, but these subtypes did not contribute to clinicopathological differences. Translocations involving BCL2, BCL6, MYC, IGH, IGK, IGL, and MALT1 were detected in 3 (12%), 3 (12%), 10 (40%), 14 (56%), 3 (12%), 3 (12%), and 0 (0%) of 25 cases, respectively. Of note, the presence of IGH translocation was significantly associated with better overall survival (P = .0053) and progression free survival (P = .0259). Similarly, the translocation involving at least one of the IGs (IGH, IGK, and/or IGL) was associated with more favorable prognosis in DLBCLs or even in DLBCL, NOS. This is the first report to reveal that a small subset of colorectal DLBCL corresponds to double-hit lymphoma. In addition, translocations involving at least one of the IGs may be a favorable prognostic factor in colorectal DLBCL. Testing the translocation involving rearrangement of IGs as well as MYC and BCL2/BCL6 may thus be useful for diagnosis and prognosis.

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.

Clinical and genetic characterization of de novo double-hit B cell precursor leukemia/lymphoma

The 2016 revised World Health Organization (WHO) classification of lymphoid neoplasms included the category of high-grade B cell lymphomas (HGBLs) with combined MYC and BCL2 and/or BCL6 rearrangements (double-hit, DH). However, the clinical features of B cell precursor leukemia (BCP-ALL) that harbor DH genetics remain widely unknown. We performed a retrospective analysis of the German Multicenter Study Group for Adult ALL registry and a literature search for de novo DH-BCP-ALLs. We identified 6 patients in the GMALL registry and 11 patients published in the literature between 1983 and June 2018. Patients of all ages (range, 15-86 years) are affected. There is a high incidence of meningeal disease and other extramedullary disease manifestations. Current treatment approaches are mainly ALL-based and are sufficient to induce first complete remissions, but progression-free survival is only 4.0 months (95% CI, 1.5-6.5 months) and all patients succumb to their disease, once relapsed, with a median survival of 5.0 months (95% CI, 3.1-6.9 months), despite intensive salvage and targeted therapy approaches. Of all patients, only two that attained an initial complete remission were alive at data cutoff. In all cases, the BCL2 gene was rearranged to be in proximity to the IGH locus, whereas MYC had various translocation partners juxtaposed. There was no significant survival difference between IG and non-IG translocation partners (HR, 1.03; 95% CI, 0.33-3.2; p = 0.89). In conclusion, de novo DH-BCP-ALL is an aggressive B cell malignancy with deleterious outcome. Physicians have to be aware of this rare disease subset due to the atypical clinical behavior and especially because latest classification systems do not cover this sub-entity.

Novel risk stratification of de novo diffuse large B cell lymphoma based on tumour-infiltrating T lymphocytes evaluated by flow cytometry

The prognostic value of tumour-infiltrating T lymphocytes (TIL-Ts) has been demonstrated in many solid tumours but remained unclear in diffuse large B cell lymphoma (DLBCL). We conducted a retrospective cohort study reviewing the TIL-Ts proportion and CD4:CD8 of 66 de novo DLBCL by flow cytometry to construct a risk stratification based on TIL-Ts-related prognostic factors. In univariate analysis, low TIL-Ts (< 14%) was significantly related to shorter survival (HR = 2.58, 95% CI 1.11-5.99, p = 0.028). In multivariate analysis, low TIL-Ts (HR = 6.48, 95% CI 2.16-19.46, p = 0.001) and high CD4:CD8 (> 1.2) (HR = 4.22, 95% CI 1.43-12.35, p = 0.009) were independent risk factors. For the risk stratification, three groups were defined based on TIL-Ts-related risk factors: low-risk group (high TIL-Ts and low CD4:CD8), intermediate risk group (low TIL-Ts, low CD4:CD8 or high TIL-Ts, high CD4:CD8) and high-risk group (low TIL-Ts and high CD4:CD8). The patients in high-risk group have significantly shorter survival than that in intermediate risk group (p = 0.025) and low-risk group (p = 0.002). This new risk stratification which is independent of performance status and age of the patients could hint the prognosis and may guide treatment of DLBCL.

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.

"Triple hit" lymphomas: A retrospective cytology case series of an uncommon high grade B-cell malignancy with C-MYC, BCL-2 and BCL-6 rearrangements

The Revised fourth Edition World Health Organization (WHO) Classification of Tumors of Hematopoietic and Lymphoid Tissues suggests novel categories, including "high grade B-cell lymphoma with MYC and BCL2 and BCL6 gene rearrangements." These diseases are known colloquially as "double hit" and "triple hit" lymphomas. The "first-hit" in these cases is the harboring of a MYC rearrangement. Concurrent derangements of BCL2 and BCL6 can be the "second-hit" or "third-hit." To our knowledge, this is the first report of "triple-hit" lymphomas in cytology specimens. The files of the Cleveland Clinic (January 2007 through December 2017) were searched for all "triple hit" lymphomas. Four cases met inclusion criteria (cytology slides in files and histologically confirmed "triple hit" lymphoma). All slides were reviewed. The mean age was 65 years, with a male predominance. All patients presented at advanced stage and showed progressive disease despite therapy. FISH studies (histologic sections) confirmed translocations of MYC (8q24), BCL2 (18q21) and BCL6 (3q27) in all patients. All cases were characterized by high cellularity, dispersed cells, presence of stripped nuclei, lymphoglandular bodies, apoptotic bodies, cytomegaly, nucleomegaly, nuclear envelope irregularities, macronucleoli (most often single), recognizable mitoses and presence of cytoplasmic vacuoles (variable). The WHO recommends that all large B-cell lymphomas be investigated using cytogenetic or molecular techniques. Concurrent inhibition of MYC and BCL2 is a potentially effective treatment strategy for triple hit lymphomas, and an expanding literature exists regarding predictive biomarkers and therapeutic regimens. It is our intention to raise awareness of this uncommon mature B-cell neoplasm within the cytodiagnostic community.

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.