Mediastinal gray zone lymphoma: the missing link between classic Hodgkin's lymphoma and mediastinal large B-cell lymphoma

What is new in the 5th edition of the World Health Organization classification of mature B and T/NK cell tumors and stromal neoplasms?

The classification of tumors is essential in the diagnosis and clinical management of patients with malignant neoplasms. The World Health Organization (WHO) provides a globally applicable classification scheme of neoplasms and it was updated several times. In this review, we briefly outline the cornerstones of the upcoming 5th edition of the World Health Organization Classification of Haematolymphoid Tumours on lymphoid neoplasms. As is adopted throughout the 5th edition of the WHO classification of tumors of all organ systems, entities are listed by a hierarchical system. For the first time, tumor-like lesions have been included in the classification, and modifications of nomenclature for some entities, revisions of diagnostic criteria or subtypes, deletion of certain entities, and introduction of new entities are presented along with mesenchymal lesions specific to the stroma of lymph nodes and the spleen. In addition to specific outlines on constitutional and somatic genetic changes associated with given entities, a separate chapter on germline predisposition syndromes related to hematologic neoplasms has been added.

New classifications of B-cell neoplasms: a comparison of 5th WHO and International Consensus classifications

In 2024, the World Health Organization (WHO) launched a new classification of lymphoid neoplasms, a revision of the previously used Revised 4th Edition of their classification (WHO-4R). However, this means that two classifications are now in simultaneous use: the 5th Edition of the WHO classification (WHO-5) and the International Consensus Classification (ICC). Instead of a comprehensive review of each disease entity, as already described elsewhere, this review focuses on revisions made in both the WHO-5 and ICC from WHO-4R and discrepancies between them regarding B-cell neoplasms. Similarities include cutaneous marginal zone lymphoma, cold agglutinin disease, non-primary effusion lymphoma-type effusion-based lymphoma, and gray zone lymphoma. Differences include plasma cell neoplasms, high-grade B-cell lymphoma (double hit lymphoma), follicular lymphoma, LPD with immune deficiency and dysregulation, extranodal large B-cell lymphoma, transformations of indolent B-cell lymphomas, and diffuse large B-cell lymphoma, not otherwise specified. Understanding the similarities and differences between the two latest classifications will aid daily diagnostic practice and future research on lymphoid neoplasms.

The 5th edition of the World Health Organization Classification of mature lymphoid and stromal tumors - an overview and update

The purpose of this review is to give an overview on the conceptual framework and major developments of the upcoming 5th edition of the World Health Organization (WHO) Classification of Haematolymphoid tumours (WHO-HAEM5) and to highlight the most significant changes made in WHO-HAEM5 compared with the revised 4th edition (WHO-HAEM4R) of lymphoid and stromal neoplasms. The changes from the revised 4th edition include the reorganization of entities by means of a hierarchical system that is realized throughout the 5th edition of the WHO classification of tumors of all organ systems, a modification of nomenclature for some entities, the refinement of diagnostic criteria or subtypes, deletion of certain entities, and introduction of new entities. For the first time, tumor-like lesions, mesenchymal lesions specific to lymph node and spleen, and germline predisposition syndromes associated with the lymphoid neoplasms are included in the classification.

High PDL1/PDL2 gene expression correlates with worse outcome in primary mediastinal large B-cell lymphoma

Primary mediastinal B-cell lymphoma (PMBL) is an uncommon entity of aggressive B-cell lymphoma with an unusually good prognosis, except for 10-15% of chemotherapy-refractory cases. To identify earlier these higher risk patients, we performed molecular characterization of a retrospective multicenter cohort of patients treated with firstline immunochemotherapy. The traits of the patients with gene-expression profiling data (n = 120) were as follows: median age of 34 years (range, 18-67 years); female sex, 58.3%; elevated lactate dehydrogenase, 82.5%; Eastern Cooperative Oncology Group performance status score of 0 to 1, 85.7%; Ann Arbor stage I/II, 55%; International Prognostic Index score of 1 to 2, 64.4%; and median metabolic tumor volume, 290.4 cm3 (range, 15.7-1147.5 cm3). Among all 137 markers tested for correlation with survival data, only programmed death-ligand (PDL) 1 and PDL2 expression showed a prognostic impact. Overall, both PDL1 and PDL2 genes were highly expressed in 37 patients (30.8%; PDL1high/PDL2high). The baseline clinical characteristics of patients with PDL1high/PDL2high were similar to those of other patients. In univariate analysis, PDL1high/PDL2high status was associated with poor progression-free survival (PFS) (hazard ratio [HR], 4.292) and overall survival (OS; HR, 8.24). In multivariate analysis, PDL1high/PDL2high status was an independent prognostic factor of adverse outcomes (PFS: HR, 5.22; OS: HR, 10.368). We validated these results in an independent cohort of 40 patients and confirmed the significant association between PDL1high/PDL2high status and inferior PFS (HR, 6.11). High PDL1/PDL2 gene expression defines a population with strong immune privilege and poorer outcomes from standard chemotherapy who might benefit from firstline checkpoint inhibitor therapy.

Brentuximab vedotin plus AVD followed by involved-node radiotherapy in a patient with classic Hodgkin lymphoma following gray zone lymphoma after autologous stem-cell transplantation failure

BACKGROUND

No consensus has been reached yet concerning treatment strategies for a sequential classic Hodgkin lymphoma (CHL) following gray zone lymphoma (GZL). Prognosis of GZL after a failed autologous hematopoietic stem-cell transplantation (auto-HCT) is poor and treatment strategy is very limited. As yet there are limited data showing clinical outcomes of brentuximab vedotin (BV) for GZL, especially for sequential CHL after GZL.

CASE PRESENTATION

We report a case of CHL following primary refractory GZL after a failed auto-HCT and showed favorable response to first-line CHL-directed chemoradiotherapy consisting of BV plus doxorubicin, vinblastine, and dacarbazin (AVD) followed by irradiation. The sequential cases with an early evolution, whose diagnosis of second lymphoma was made within a year, have been recently reported very poor survival shorter than a year. Whether a sequential CHL following GZL should be treated as a primary or relapsed disease has not been clearly elucidated. Our patient showed favorable response to first-line CHL-directed chemoradiotherapy without allogenic hematopoietic stem-cell transplantation and has in continuous remission for 2 years.

CONCLUSIONS

The management of our case could help for physicians to make better treatment decisions and provide insights for further exploration in future studies.

Evolution of Lymphoma Diagnosis in the Era of Personalized Medicine: A Marriage of Pathology and Genomics for Clinical Practice

The modern taxonomy of disease builds a framework for precision medicine, by which traditional pathologic criteria are integrated with clinical and genomic features to define disease entities. Two of the most common subtypes of lymphoma on a worldwide basis are follicular lymphoma (FL) and diffuse large B-cell lymphoma. Although BCL2 translocation is the signature lesion of most nodal FL, recent studies have identified significant diversity among follicle center-derived lesions. BCL2-negative FL is a genetically heterogeneous disease that occurs in both nodal and extranodal sites. Several distinct entities have been recognized in the pediatric age group, including pediatric-type FL, testicular FL, and interferon regulatory factor 4 (IRF4)-rearranged large B-cell lymphoma. Diffuse large B-cell lymphoma is a family of aggressive B-cell neoplasms with marked variation in pathogenesis and clinical features. Gene expression profiling >20 years ago identified the cell of origin as a key discriminator, but more recently high-throughput sequencing has identified highly varied mutational profiles that point the way in the future toward improvements in targeted therapy and patient outcome.

Mediastinal large B cell lymphoma and surrounding gray areas: a report of the lymphoma workshop of the 20th meeting of the European Association for Haematopathology

Session 3 of the 2021 European Association for Haematopathology/Society for Hematopathology Workshop focused on mediastinal large B cell lymphomas and surrounding gray areas. One half of the session was dedicated to primary mediastinal large B cell lymphoma (PMBL) and included cases with classic clinicopathologic features, as well as cases with either morphologic or immunophenotypic variation, and PMBL-like cases with primary extramediastinal disease. The role of additional immunophenotyping and/or molecular testing to aid in the diagnosis of PMBL was discussed. The second half of the session focused on mediastinal and non-mediastinal gray zone lymphomas (GZL) with features intermediate between diffuse large B cell lymphoma (DLBCL) and classic Hodgkin lymphoma (CHL). Several cases illustrating the current challenges in separating this entity from PMBL/DLBCL and CHL were presented. There was discussion regarding the clinical and genetic differences between mediastinal and non-mediastinal GZLs. Rare cases of PMBL and GZL associated with EBV or follicular lymphoma were reviewed. Finally, several cases included in the session highlighted composite or sequential CHL and PMBL/DLBCL and/or GZL, highlighting challenges in separating such cases from GZL.

Immunoglobulin light chain transcript detection by ultrasensitive RNA in situ hybridization for B-cell lymphoma diagnosis

Evaluation of B-cell clonality can be challenging in the interpretation of lymphoid infiltrates on tissue sections. Clonality testing based on IG gene rearrangements analysis by PCR (IG-PCR) is the gold standard. Alternatively, B-cell clonality can be assessed by the recognition of immunoglobulin light chain (IgLC) restriction, by immunohistochemistry (IHC), chromogenic in situ hybridization (ISH) or flow cytometry (FC). IG-PCR requires molecular facilities, and FC requires cell suspensions, both not widely available in routine pathology units. This study evaluates the performance of B-cell clonality detection by IgLC-RNAscope® (RNAsc) in a group of 216 formalin-fixed, paraffin-embedded samples including 185 non-Hodgkin B-cell lymphomas, 11 Hodgkin lymphomas (HL) and 20 reactive samples. IgLC-RNAsc, performed in parallel with FC in 53 cases, demonstrated better performances (93% vs 83%), particularly in diffuse large B-cell lymphoma (98% vs 71%) and follicular lymphoma (93% vs 83%) diagnosis. IgLC-RNAsc was also superior to IHC and ISH especially in samples with limited tumor cell content, where IG-PCR was not informative. Performed for the first time on mediastinal lymphomas, IgLC-RNAsc identified monotypic IgLC transcripts in 69% of primary mediastinal large B-cell lymphoma (PMBCL) and 67% of mediastinal gray zone lymphomas (MGZL). IGK/L double-negative cells were detected in 1 PMBCL, 2 MGZL, and all classical HL, while monotypic IgLC expression appeared to be a hallmark in nodular lymphocyte-predominant HL. IgLC-RNAsc demonstrates to be a powerful tool in B-cell lymphoma diagnosis, above all in challenging cases with limited tumor cell content, ensuring in situ investigations on mechanisms of Ig regulation across lymphoma entities.

Abnormal Presentation and Challenging Diagnosis of Mediastinal Lymphoma: A Case Report

We describe a rare case of classical Hodgkin lymphoma (HL) in a 20-year-old female patient. She presented to our hospital with chest wall swelling after months of post-chest trauma management. The swelling was initially treated as an infected hematoma, and the patient was referred for surgical evacuation. During the surgery, the swelling was found to be a mass that extended to the mediastinum. A biopsy was taken, which later resulted in the diagnosis of a granular cell tumor (GCT). A decision on surgical resection by video-assisted thoracoscopic surgery (VATS) was taken after discussion with the multidisciplinary team of surgery, cardiothoracic surgery, oncology, pathology, and radiology. During the surgery, a frozen section biopsy was taken, which showed no features of lymphoma or granular cell tumors. The surgery was followed by a midline sternotomy to control the bleeding from an accidentally injured major vessel. The bleeding was controlled, and the mass was dissected and sent for histopathological examination. The histopathology showed nodular classical HL features, and the patient was referred for chemotherapy. In our case, the patient was initially diagnosed with GCT, but with complete resection and an adequate biopsy, the mass was found to be a classical HL. Possible cross-cellularity is questioned, and the possible correlation between the two findings encouraged us to report this case.

Mediastinal gray zone lymphoma in a pregnant woman presenting with cardiac tamponade

BACKGROUND

Mediastinal gray zone lymphoma is a newly recognized rare B cell neoplasm, which is challenging in diagnosis and treatment.

CASE PRESENTATION

In the current study, we aimed to report a 25-year-old pregnant woman at 25 weeks of gestation who presented with chronic cough and progressive shortness of breath, hypotension, tachycardia, and tachypnea. A large circumferential pericardial effusion with compressive effect on the right atrium and right ventricle and a large extracardiac mass with external pressure to mediastinal structures were seen on trans thoracic echocardiography. The emergency pericardiocentesis was performed with the diagnosis of cardiac tamponade. Also, CMR revealed a huge heterogeneous anterior mediastinal mass, and the pathology and the immunohistochemistry of the mass biopsy revealed gray zone lymphoma with positive CD3, CD20, CD30, CD45, PAX5, and negative CD15 expression. Three courses of chemotherapy with the CHOP regimen were performed with an acceptable response every three weeks before delivery. A caesarian section was performed at 37 weeks without any problem for the patient and fetus, and chemotherapy will be started three weeks after delivery.

CONCLUSION

Cardiac tamponade as an emergency condition occurred in this pregnant patient by malignant pericardial effusion and mediastinal mass pressure. Accurate diagnosis and on time interventions caused a significant improvement and a successful delivery.

The MAL Family of Proteins: Normal Function, Expression in Cancer, and Potential Use as Cancer Biomarkers

The MAL family of integral membrane proteins consists of MAL, MAL2, MALL, PLLP, CMTM8, MYADM, and MYADML2. The best characterized members are elements of the machinery that controls specialized pathways of membrane traffic and cell signaling. This review aims to help answer the following questions about the MAL-family genes: (i) is their expression regulated in cancer and, if so, how? (ii) What role do they play in cancer? (iii) Might they have biomedical applications? Analysis of large-scale gene expression datasets indicated altered levels of MAL-family transcripts in specific cancer types. A comprehensive literature search provides evidence of MAL-family gene dysregulation and protein function repurposing in cancer. For MAL, and probably for other genes of the family, dysregulation is primarily a consequence of gene methylation, although copy number alterations also contribute to varying degrees. The scrutiny of the two sources of information, datasets and published studies, reveals potential prognostic applications of MAL-family members as cancer biomarkers-for instance, MAL2 in breast cancer, MAL2 and MALL in pancreatic cancer, and MAL and MYADM in lung cancer-and other biomedical uses. The availability of validated antibodies to some MAL-family proteins sanctions their use as cancer biomarkers in routine clinical practice.

Large B-Cell Lymphomas in the 5th Edition of the WHO-Classification of Haematolymphoid Neoplasms-Updated Classification and New Concepts

The family/class of the large B-cell lymphomas (LBCL) in the 5th edition of the World Health Organization (WHO) classification of haematolymphoid tumors (WHO-HAEM5) features only a few major changes as compared to the 4th edition. In most entities, there are only subtle changes, many of them only representing some minor modifications in diagnostic terms. Major changes have been made in the diffuse large B-cell lymphomas (DLBCL)/high-grade B-cell lymphomas (HGBL) associated with MYC and BCL2 and/or BCL6 rearrangements. This category now consists of MYC and BCL2 rearranged cases exclusively, while the MYC/BCL6 double hit lymphomas now constitute genetic subtypes of DLBCL, not otherwise specified (NOS) or of HGBL, NOS. Other major changes are the conceptual merger of lymphomas arising in immune-privileged sites and the description of LBCL arising in the setting of immune dysregulation/deficiency. In addition, novel findings concerning underlying biological mechanisms in the pathogenesis of the different entities are provided.

[Classification of Hodgkin lymphoma and related entities : News and open questions]

Two new classifications were recently released: the 5th edition of the WHO classification of hematolymphoid tumors and the International Consensus Classification (ICC) drafted by the Clinical Advisory Committee. In the preparation of both classifications, the previously existing lymphoma categories were reevaluated according to recently obtained data on clinical, morphological, and molecular findings. In this review we summarize the current placements of classic and nodular lymphocyte predominant Hodgkin lymphoma and their relevant differential diagnoses.

Targeted Mutational Profiling Reveals Clonal Relationships in Metachronous Occurrence of Classic Hodgkin and Mediastinal Large B-Cell Lymphomas

Classic Hodgkin lymphoma (CHL) patients may infrequently present with a prior or recurrent disease with discordant histology resembling non-Hodgkin lymphomas. These include primary mediastinal large B-cell lymphoma (PMBL), diffuse large B-cell lymphoma (DLBCL), or mediastinal gray-zone lymphoma (MGZL). Such patients are often refractory to standard therapy and their diagnosis is hampered by significant morphologic and immunophenotypic overlap and insufficient molecular data. Among 509 CHL patients seen at an academic medical center, 6 patients had a prior or subsequent diagnosis different from CHL. Paired tissue samples were evaluated by targeted mutational analysis using a 164-gene panel. Our findings show multiple shared variants indicative of a clonal relationship between the CHL and the PMBL, DLBCL, or MGZL diagnoses. Most frequent mutated genes included TNFAIP3 (4 of 6, 66.7%), STAT6 (3 or 6, 50%), ARID1A (3 of 6, 50%), and XPO1 (3 of 5, 60%). Three patients showed the same oncogenic variant within the XPO1 gene (E571K), and mutations in TNFAIP3 and B2M were observed in 2 of the 5 patients with shared variants. In addition, differences in the mutation profile between the lymphoma pairs were also observed, which could represent clonal evolution. Mutational profiling could be of benefit in patients with recurrent/refractory disease with discordant histology, where the clonal relationship could be helpful to inform and guide therapeutic decisions. These findings provide further evidence of a true biological continuum surrounding CHL, PMBL, DLBCL, and MGZL and shed light on underlying genetic events and their clinical impact.

Evolution in the definition and diagnosis of the Hodgkin lymphomas and related entities

Hodgkin lymphoma was the first of the lymphomas to be recognized as a specific disease entity. However, recent studies have highlighted the heterogeneity of the diseases associated with this eponym warranting clarification and refinement of diagnostic terminology. While classic Hodgkin lymphoma (CHL) remains an essentially unchanged diagnostic entity in the 2022 International Consensus Classification of Mature Lymphoid Neoplasms (2022 ICC), nodular lymphocyte predominant Hodgkin lymphoma (NLPHL) is now renamed nodular lymphocyte predominant B cell lymphoma (NLPBL) in recognition of the distinct pathologic, biologic, and clinical differences. Fan patterns A, B, and C (sharing the presence of evident follicular structures, and retention of a B cell rich background) will be combined in "typical" or grade 1, while the other "variant" patterns, D, E, and F, are considered grade 2. T-cell/histiocyte-rich large B cell lymphoma (THRBCL) is considered part of the "variant" NLPHL continuum.The entity previously known as "B cell lymphoma, unclassifiable (BCLU), with features intermediate between diffuse large B cell lymphoma (DLBCL) and CHL" has been renamed "mediastinal gray zone lymphoma" (MGZL) in recognition of the importance of the thymic niche in the biology of this tumor. The diagnostic criteria for MGZL have been refined and require both a high tumor cell density and a strongly preserved B cell program.This article will describe updates on CHL, NLPBL, and MGZL in the recently published 2022 ICC and provide some useful differential diagnostic clues in cases with atypical morphology or immunophenotype.

Plasticity in Classical Hodgkin Composite Lymphomas: A Systematic Review

The co-occurrence of several lymphomas in a patient defines composite/synchronous lymphoma. A common cellular origin has been reported for both contingents of such entities. In the present review, we aimed to gather the available data on composite lymphomas associating a classical Hodgkin lymphoma (cHL) with another lymphoma, to better understand the plasticity of mature B and T-cells. This review highlights that >70% of patients with a composite lymphoma are ≥55 years old, with a male predominance. The most reported associations are cHL with follicular lymphoma or diffuse large B-cell lymphoma, with over 130 cases reported. The cHL contingent is often of mixed cellularity type, with a more frequent focal/weak CD20 expression (30% to 55.6%) compared to de novo cHL, suggesting a particular pathophysiology. Moreover, Hodgkin cells may express specific markers of the associated lymphoma (e.g., BCL2/BCL6 for follicular lymphoma and Cyclin D1 for mantle cell lymphoma), sometimes combined with common BCL2/BCL6 or CCND1 rearrangements, respectively. In addition, both contingents may share similar IgH/IgK rearrangements and identical pathogenic variants, reinforcing the hypothesis of a common clonal origin. Finally, cHL appears to be endowed with a greater plasticity than previously thought, supporting a common clonal origin and a transdifferentiation process during lymphomagenesis of composite lymphomas.

Hodgkin Lymphoma: Biology and Differential Diagnostic Problem

Hodgkin lymphomas (HLs) are lymphoid neoplasms that are morphologically defined as being composed of dysplastic cells, namely, Hodgkin and Reed–Sternberg cells, in a reactive inflammatory background. The biological nature of HLs has long been unclear; however, our understanding of HL-related genetics and tumor microenvironment interactions is rapidly expanding. For example, cell surface overexpression of programmed cell death 1 ligand 1 (CD274/PD-L1) is now considered a defining feature of an HL subset, and targeting such immune checkpoint molecules is a promising therapeutic option. Still, HLs comprise multiple disease subtypes, and some HL features may overlap with its morphological mimics, posing challenging diagnostic and therapeutic problems. In this review, we summarize the recent advances in understanding the biology of HLs, and discuss approaches to differentiating HL and its mimics.

The Grey Zones of Classic Hodgkin Lymphoma

Simple Summary

Classic Hodgkin lymphoma (CHL) is a well-defined lymphoid neoplasm with a minority of characteristic neoplastic cells of B cell origin, namely Hodgkin and Reed–Sternberg cells immersed in a rich reactive inflammatory infiltrate in the background. Although CHL has always been set apart from non-Hodgkin lymphomas, cases with morphological and phenotypic features intermediate between CHL and other lymphomas have been described. Whereas some of these lymphomas only represent morphological mimics, others exhibit mutational and gene expression profiles which overlap with CHL, indicating that these cases, frequently termed grey zone lymphomas, reside on the biological boundary between CHL and large B-cell lymphomas. In the present review, we aim to describe the current knowledge of these rare lymphomas, address diagnostic issues and summarize today’s concepts on the classification of grey zone lymphomas and related tumors.

Abstract

Classic Hodgkin lymphoma (CHL) is a well-defined neoplasm characterized by the presence of a minority of pathognomonic Hodgkin and Reed–Sternberg (HRS) cells in a reactive inflammatory background. Although genotypically of B cell origin, HRS cells exhibit a downregulated B cell program and therefore are set apart from other B cell lymphomas in the current WHO classification. However, cases with morphological and phenotypic features overlapping with CHL have been recognized, and the category of B cell lymphoma—unclassifiable—with features intermediate between diffuse large B cell lymphoma (DLBCL) and CHL, also termed grey zone lymphoma, was first introduced into the WHO classification in 2008 as provisional entity. These cases, as well as others raising a differential diagnosis of CHL can present diagnostic problems, as well as therapeutic challenges. Whereas some of these lymphomas only represent biologically unrelated morphological mimics, others, especially mediastinal grey zone lymphoma, exhibit genetic and gene expression profiles which overlap with CHL, indicating a true biological relationship. In this review, we address areas of diagnostic difficulties between CHL and other lymphoma subtypes, discuss the biological basis of true grey zone lymphoma based on recent molecular studies and delineate current concepts for the classification of these rare tumors.

Diagnostic utility of programmed cell death ligand 1 (clone SP142) immunohistochemistry for malignant lymphoma and lymphoproliferative disorders: A brief review

The programmed cell death 1 (PD1)/PD1 ligand (PD-L1) axis plays an important role in tumor cell escape from immune control and has been most extensively investigated for therapeutic purposes. However, PD-L1 immunohistochemistry is still not used widely for diagnosis. We review the diagnostic utility of PD-L1 (by clone SP142) immunohistochemistry in large-cell lymphomas, mainly consisting of classic Hodgkin lymphoma (CHL) and diffuse large B-cell lymphoma (DLBCL). Neoplastic PD-L1 (nPD-L1) expression on Hodgkin and Reed-Sternberg cells is well-established among prototypic CHL. Of note, EBV+ CHL often poses a challenge for differential diagnosis from peripheral T-cell lymphoma with EBV+ non-malignant large B-cells; their distinction is based on the lack of PD-L1 expression on large B-cells in the latter. The nPD-L1 expression further provides a good diagnostic consensus for CHL with primary extranodal disease conceivably characterized by a combined pathogenesis of immune escape of tumor cells and immunodeficiency. Compared with CHL, the nPD-L1 expression rate is much lower in DLBCL, highlighting some specific subgroups of intravascular large B-cell lymphoma, primary mediastinal large B-cell lymphoma, and EBV+ DLBCL. They consist of nPD-L1-positive and -negative subgroups, but their clinicopathological significance remains to be elucidated. Microenvironmental PD-L1 positivity on immune cells may be associated with a favorable prognosis in extranodal DLBCL. PD-L1 (by SP142) immunohistochemistry has helped us to understand the immune biology of lymphoid neoplasms possibly related by immune escape and/or immunodeficiency. However, knowledge of these issues remains limited and should be clarified for diagnostic consensus in the future.

EBV-Positive Primary Large B-Cell Lymphoma: The Role of Immunohistochemistry and XPO1 in the Diagnosis of Mediastinal Lymphomas

Primary mediastinal (thymic) large B-cell lymphoma (PMBL) is described as almost always negative for Epstein-Barr virus (EBV). In the context of a mediastinal lymphoma, the distinction between PMBL, classical Hodgkin lymphoma, diffuse large B-cell lymphoma, and mediastinal gray-zone lymphoma can be very difficult; hence, EBV positivity often argues against PMBL. We present a 19-year-old man with mediastinal mass morphologically consistent with PMBL. The tumor expressed classic immunophenotype, including positivity for CD20, CD19, MAL, OCT2, BOB1, BCL6, CD79a, and subset positivity for CD30. However, the tumor was EBV-positive by in situ hybridization. Next-generation sequencing detected somatic mutations in XPO1 (E571K), SMARCB1 (L356fs), and MYCC (T73A). Although the immunophenotype and XPO1 mutation are characteristic of PMBL, EBV expression is uncommon. Since EBV positivity can occur in rare PMBLs, it should not be the deciding factor in the diagnosis. This is the first EBV-positive PMBL in which mutational profiling has been reported. Aside from providing diagnostic support, the finding of the XPO1 E571K mutation may suggest a targeted therapeutic option.

Concomitant occurrence of genetically distinct Hodgkin lymphoma and primary mediastinal lymphoma

Synchronous Hodgkin Lymphoma and Primary Mediastinal B-cell Lymphoma is possible, with molecular analyses proving the absence of clonal filiation between both entities. This suggests a common etiology but the existence of two divergent clones.

Survival among patients with composite and sequential lymphoma between primary mediastinal lymphoma/diffuse large B-cell lymphoma and classical Hodgkin lymphoma: A population-based study

BACKGROUND

Data on composite and sequential lymphoma between primary mediastinal lymphoma/diffuse large B-cell lymphoma (LBCL) and classical Hodgkin lymphoma (cHL) are rare.

METHODS

We identified 25 cases with composite lymphoma (CL), 116 cases developing LBCL as a second primary cancer after cHL (cHL-LBCL), and 74 cases developing cHL as a second primary cancer after LBCL (LBCL-cHL) from the Surveillance, Epidemiology, and End Results (SEER) 18 database. Comparisons of overall survival (OS) and lymphoma cause-specific survival (CSS) between patients with cHL-LBCL or cHL-LBCL and their de novo counterparts were performed.

RESULTS

The 5-year OS of patients with CL was 74.8 %. No significant difference in unadjusted OS and lymphoma CSS were observed between patients with de novo LBCL (LBCL-1 group) and patients with cHL-LBCL. However, the age- and stage-adjusted cHL-LBCL group had inferior OS and lymphoma CSS compared with that in the LBCL-1 group. The unadjusted and adjusted OS and lymphoma CSS in the LBCL-cHL group were significantly worse than patients with de novo cHL.

CONCLUSIONS

CL between LBCL and cHL may have good outcomes. cHL survivors had poorer outcomes after a LBCL diagnosis versus patients with LBCL-1. Significantly poor outcomes were observed in patients with LBCL-cHL compared with patients with de novo cHL.

Lymphoma Classification

Twenty-five years after the Revised European American Classification of Lymphoid Neoplasms classification was published, its principle of an integrative approach to disease definition based on several parameters still prevails and has been adopted and expanded in the following World Health Organization classifications of tumors of the hematopoietic organs. The latest World Health Organization classification revised in 2017 comprises more than 80 entities of mature lymphoid neoplasms (B-cell, T-cell, and Hodgkin lymphomas), which are defined according to their morphology, immunophenotype, genetic lesions and molecular profiles, clinical features, and cellular derivation. The classification also recognizes both incipient and indolent lymphoid neoplasms with a low potential of progression. In this review, we highlight some of the new data and recent modifications introduced in the 2017 classification.

The MAL Protein, an Integral Component of Specialized Membranes, in Normal Cells and Cancer

The MAL gene encodes a 17-kDa protein containing four putative transmembrane segments whose expression is restricted to human T cells, polarized epithelial cells and myelin-forming cells. The MAL protein has two unusual biochemical features. First, it has lipid-like properties that qualify it as a member of the group of proteolipid proteins. Second, it partitions selectively into detergent-insoluble membranes, which are known to be enriched in condensed cell membranes, consistent with MAL being distributed in highly ordered membranes in the cell. Since its original description more than thirty years ago, a large body of evidence has accumulated supporting a role of MAL in specialized membranes in all the cell types in which it is expressed. Here, we review the structure, expression and biochemical characteristics of MAL, and discuss the association of MAL with raft membranes and the function of MAL in polarized epithelial cells, T lymphocytes, and myelin-forming cells. The evidence that MAL is a putative receptor of the epsilon toxin of Clostridium perfringens, the expression of MAL in lymphomas, the hypermethylation of the MAL gene and subsequent loss of MAL expression in carcinomas are also presented. We propose a model of MAL as the organizer of specialized condensed membranes to make them functional, discuss the role of MAL as a tumor suppressor in carcinomas, consider its potential use as a cancer biomarker, and summarize the directions for future research.

"Do Not Ignore Musculoskeletal Pain"-Initial Presentation of a Rare Malignant Disease: Case Report and Literature Review

Gray zone lymphoma, also known as B-cell lymphoma, unclassifiable, with features intermediate between diffuse large B-cell lymphoma and classical Hodgkin lymphoma, is a rare malignancy with overlapping features of both diffuse large B-cell lymphoma and classical Hodgkin lymphoma. Most commonly mediastinal involvement is seen. Extranodal involvement is rare. In this case report, we present the case of a 59-year-old male who presented with stress-related left shoulder pain, ultimately diagnosed with gray zone lymphoma. The patient was treated with etoposide, prednisone, vincristine, cyclophosphamide, and doxorubicin-rituximab (EPOCH-R) regimen followed by consolidation radiotherapy resulting in complete response. We are highlighting this case as rare and atypical presentation of a rare disease.

Brentuximab vedotin maintenance after autologous stem cell transplantation for refractory gray zone lymphoma with long-term remission

Gray zone lymphoma (GZL) is a rare type of B-cell lymphoma characterized by features of both diffuse large B-cell lymphoma and classical Hodgkin lymphoma (cHL). The prognosis of GZL is poorer than that of cHL and mediastinal large B-cell lymphoma. However, an optimal treatment strategy for relapsed/refractory (R/R) GZL has not been established in the clinical setting. The current study reported an excellent clinical response in a patient with R/R CD30-positive GZL who received brentuximab vedotin (BV) maintenance after autologous stem cell transplantation (ASCT). Although the patient was resistant to prior treatments, BV maintenance after ASCT achieved long-term remission. Hence, BV was determined to be a safe and effective therapeutic option for CD30-positive R/R GZL.

Transition Between Diffuse Large B-Cell Lymphoma and Classical Hodgkin Lymphoma- Our Histopathological and Clinical Experience With Patients With Intermediate Lymphoma

Even though information about the pathophysiology and clinical features of grey-zone lymphoma, an entity intermediate between classical Hodgkin lymphoma and diffuse large B-cell lymphoma, is growing, there are still a number of unanswered questions. The disease has no easily reproducible diagnostic criteria, which makes identification challenging. Uncommon, mixed histological picture and unusual clinical presentation should raise suspicion for grey-zone lymphoma. In this retrospective analysis we present 9 gray zone lymphoma patients, who were diagnosed in our institute between 2008 and 2018. The histological diagnoses was oftentime challenging, we asked for a revision in three cases due to the unusual clinical behavior and in other three cases only the relapse of the disease proved to be grey-zone lymphoma. Based on the initial histopathological diagnoses we applied adriablastine-bleomycine-vinblastine and procarbasine or cyclophosphamide-vincristine-adriablastine and prednisolon as first line chemotherapy regime with additional rituximab in six cases and brentuximab-vedotine in one patient. In six of the nine patients due to the primary refractory disease we used rituximab plus cisplatine, cytosine-arabinoside, prednisolone salvage treatment and five of these patients responded well enough to become eligible for autologous stem cell transplantation. One young male patient was refractory for various treatments and died due to the progression of his lymphoma. As a rare disease grey-zone lymphoma has no existing diagnostic criteria or guiedlines for its standard of care, which makes the everyday practice rather challenging for the clinicians, and emphasize the importance of unique decision making in every case and the repeated consultation between the pathologist and hematologist.

Coexistence of Hodgkin and Non-Hodgkin Lymphoma; Composite Lymphoma [CL] in a Patient Presenting with Waxing and Waning Lymphadenopathy

BACKGROUND

The coexistence of two or more types of lymphoma within the same organ at the same time of diagnosis is defined as composite lymphoma, a rare disease that has recently been identified in the literature. Pointedly, the concurrence may be Hodgkin lymphoma with a Non-Hodgkin lymphoma [NHL], either B or T cells, or two different entities of NHLs. Furthermore, this condition has been described concurrently or sequentially. In order for the diagnosis to be established, two or more distinct clones should be proven by morphological and laboratory tests.

CASE PRESENTATION

Herein, we cite a seventy-three-year old female patient with low-grade fever, waxing and waning cervical lymphadenopathy, whose biopsy of an axillary lymph node demonstrated the rare coexistence of Hodgkin and NHL, known as composite lymphoma.

CONCLUSION

Composite lymphomas pose a particular diagnostic challenge, and currently, there are no agreed standards for treatment.

An approach to small lymph node biopsies: pearls and pitfalls of reporting in the real world

Recent advances in interventional radiology have resulted in the utilization of small lymph node biopsies, including fine-needle aspiration (FNA) and core needle biopsy (CNB) as an initial diagnostic tool in hematopathology. A major challenge to the utilization of FNA and CNB is the limited-to-scant tissue often available. We propose delegation of the task of handling biopsy specimens to the laboratory staff by the biopsy operators, in order to optimize the utilization of the specimen. Furthermore, in order to effectively diagnose hematolymphoid neoplasms a variety of ancillary tests including immunohistochemistry, flow cytometry, molecular analysis, florescence in situ hybridization (FISH) are necessary. We propose morphological evaluation coupled with careful utilization of ancillary studies along with clinical correlation to approach the correct diagnosis. Our morphological assessment considers the types of proliferating cell population: mainly small cells, sheets of large cells, or scattered large cells among small cells. This is followed by employment of the corresponding immunopanel to assess the differential diagnosis in each of the three categories. We also elaborate on the importance for pathologists to become proficient in understanding the limitations of small tissue biopsies as well as the differences in interpretation, and wording their reports to help clinicians and direct them to further investigate and/or to re-biopsy when necessary.

Cell-Free DNA for the Management of Classical Hodgkin Lymphoma

Cell-free DNA (cfDNA) testing, is an emerging “liquid biopsy” tool for noninvasive lymphoma detection, and an increased amount of data are now available to use this technique with accuracy, especially in classical Hodgkin lymphoma (cHL). The advantages of cfDNA include simplicity of repeated blood sample acquisition over time; dynamic, noninvasive, and quantitative analysis; fast turnover time; reasonable cost; and established consistency with results from tumor genomic DNA. cfDNA analysis offers an easy method for genotyping the overall molecular landscape of pediatric and adult cHL and may help in cases of diagnostic difficulties between cHL and other lymphomas. cfDNA levels are correlated with clinical, prognostic, and metabolic features, and may serve as a therapeutic response evaluation tool and as a minimal residual disease (MRD) biomarker in complement to positron emission tomography (PET). Indeed, cfDNA real-time monitoring by fast high-throughput techniques enables the prompt detection of refractory disease or may help to address PET residual hypermetabolic situations during or at the end of treatment. The major recent works presented and described here demonstrated the clinically meaningful applicability of cfDNA testing in diagnostic and theranostic settings, but also in disease risk assessment, therapeutic molecular response, and monitoring of cHL treatments.

Unraveling the Mystery of Gray Zone Lymphoma in Human Immunodeficiency Virus-Seropositive Patients: Two Cases

Gray zone lymphoma (GZL) is an uncommon neoplasm with intermediate features of both classic Hodgkin lymphoma (cHL) and diffuse large B-cell lymphoma (DLBCL). It was identified in the World Health Organization (WHO) classification as its own neoplasm in 2008. Patients infected with human immunodeficiency virus (HIV) have been rarely diagnosed with this type of lymphoma and treatment strategies for this subset of patients is not well described. Here we present two cases of patients with HIV that were diagnosed with GZL in a single community-based institution. A 68-year-old male with HIV/acquired immunodeficiency syndrome (AIDS) on highly active antiretroviral therapy (HAART) presented with 6-month history of dyspnea and weight loss. Computed tomography (CT) of the chest revealed multiple lung and mediastinal lesions, the largest measuring 9.4 × 5.5 cm lesion in the right perihilar region. Lymph node biopsy revealed abnormal lymphocytes with immunohistochemistry (IHC) positive for cluster of differentiation 30 (CD30), CD20 and Epstein-Barr virus (EBV), consistent with a diagnosis of GZL. The patient received dose-adjusted etoposide, doxorubicin, vincristine, cyclophosphamide, prednisone, and rituximab (DA-EPOCH-R) and attained a complete response. He since completed maintenance rituximab therapy and remains disease-free at 33 months. A 40-year-old female with HIV/AIDS on HAART presented with high-grade fever, dyspnea, and weight loss. CT imaging revealed multiple lung lesions, hepatosplenomegaly and diffuse lymphadenopathy in the chest and abdomen. Lymph node and bone marrow biopsy revealed cells positive for CD20, CD30, and EBV within atypical lymphoid cells. With this, a diagnosis of GZL was made and she was treated with DA-EPOCH-R. She attained a complete response and was on maintenance rituximab therapy. At 9 months she relapsed, she has now received a bone marrow transplant. GZL is a rarely described neoplasm within the HIV population. Here we describe two HIV patients diagnosed with GZL that were successfully treated at our institution. DA-EPOCH-R was able to induce durable remission with limited side effects and it represents a viable strategy for treating patients in this population. Further studies need to be performed to better characterize this lymphoma, especially in HIV patients. Treatment strategies for this select group of patients also need to be better defined.

Gene expression profiling of gray zone lymphoma

Gray zone lymphoma (GZL), a B-cell lymphoma with features intermediate between large B-cell lymphoma (LBCL) and classic Hodgkin lymphoma (cHL), is a rare and poorly defined entity. Alongside GZL, a subset of Epstein-Barr virus (EBV)-positive diffuse large B-cell lymphoma (DLBCL) has been described with polymorphic/GZL-like morphology (polymorphic-EBV-L). To fill the important gap in our understanding of the pathogenic process underlying these entities, we performed a gene expression study of a large international cohort of GZL and polymorphic-EBV-L, combined with cHL and primary mediastinal large B-cell lymphoma (PMBCL) cases. In an unsupervised principal component analysis, GZL cases presented with intermediate scores in a spectrum between cHL and PMBCL, whereas polymorphic-EBV-L clustered distinctly. The main biological pathways underlying the GZL spectrum were related to cell cycle, reflecting tumor cell content, and extracellular matrix signatures related to the cellular tumor microenvironment. Differential expression analysis and phenotypic characterization of the tumor microenvironment highlighted the predominance of regulatory macrophages in GZL compared with cHL and PMBCL. Two distinct subtypes of GZL were distinguishable that were phenotypically reminiscent of PMBCL and DLBCL, and we observed an association of PMBCL-type GZL with clinical presentation in the "thymic" anatomic niche. In summary, gene expression profiling (GEP) enabled us to add precision to the GZL spectrum, describe the biological distinction compared with polymorphic-EBV-L, and distinguish cases with and without thymic involvement as 2 subgroups of GZL, namely PMBCL-like and DLBCL-like GZL.

Lymphomas of the Mediastinum and Their Differential Diagnosis

Lymphoma is the most common malignancy involving the mediastinum but can be challenging to diagnose on small biopsy specimens. This review provides a pattern-based approach to help triage small tissue samples for the diagnosis of mediastinal lymphoid proliferations, with focus on the main primary mediastinal lymphomas. The use of ancillary studies is highlighted, along with considerations to avoid misdiagnosis and scenarios to request additional tissue.

Age-related EBV-associated B-cell lymphoproliferative disorders and other EBV + lymphoproliferative diseases: New insights into immune escape and immunodeficiency through staining with anti-PD-L1 antibody clone SP142

Epstein-Barr virus (EBV) is prevalent among healthy individuals, and is implicated in numerous reactive and neoplastic processes in the immune system. The authors originally identified a series of senile or age-related EBV-associated B-cell lymphoproliferative disorders (LPD) bearing a resemblance to immunodeficiency-associated ones. These LPDs may be associated with immune senescence and are now incorporated into the revised 4th edition of 2017 WHO lymphoma classification as EBV-positive (EBV+) diffuse large B-cell lymphoma (DLBCL), not otherwise specified (NOS). These EBV+ B-cells often have a Hodgkin/Reed-Sternberg (HRS)-like appearance and are shared beyond the diagnostic categories of mature B-cell neoplasms, mature T-cell neoplasms, classic Hodgkin lymphoma, and immunodeficiency-associated LPD. In addition, peculiar new diseases, such as EBV+ mucocutaneous ulcer and EBV+ DLBCL affecting the young, were recognized. On the other hand, lymphoma classification is now evolving in accord with deeper understanding of the biology of programmed death ligand 1 (PD-L1). Assessing PD-L1 positivity by staining with the anti-PD-L1 monoclonal antibody SP142 provides new insight by discriminating between immune evasion and senescence or immunodeficiency. The aim of the present review is to briefly summarize the diagnostic use of immunostaining with SP142 in malignant lymphomas and/or LPDs that feature tumor and nonmalignant large B-cells harboring EBV.

Diagnostic utility of STAT6YE361 expression in classical Hodgkin lymphoma and related entities

Although the distinction of classical Hodgkin lymphoma from nodular lymphocyte predominant Hodgkin lymphoma using morphology and immunostains is straightforward in most instances, occasional cases pose diagnostic challenge. We sought to determine the utility of the novel YE361 STAT6 rabbit monoclonal antibody in Hodgkin lymphoma and diagnostically challenging B- and T-cell non-Hodgkin lymphoma entities with Hodgkin-like features. Cases from seven institutions included: 57 classical Hodgkin lymphomas (31% EBV+), 34 nodular lymphocyte predominant Hodgkin lymphomas, 34 mimicking B- and T-cell non-Hodgkin lymphomas, and 7 reactive lymphoproliferations. After review of histology, STAT6^YE361 immunostaining was performed. The intensity and spatial localization of immunopositivity was assessed in neoplastic cells. Additional FISH for programmed death ligand-1 (PD-L1) was performed in one patient in paired treatment-naive and relapse biopsy tissues. Two STAT6^YE361 immunopositive cases were examined by whole-exome sequencing after flow sorting to assess mutations in STAT6 pathway genes. Most classical Hodgkin lymphomas showed nuclear staining for STAT6^YE361 [46/57 cases (80%)] on Hodgkin cells. Staining was exclusively nuclear in a minority [12/46 (26%)], while dual nuclear and cytoplasmic localization was more common [34/46 (74%)]. In contrast, all nodular lymphocyte predominant Hodgkin lymphomas [0/34 (0%)] were negative for nuclear STAT6^YE361 staining on the lymphocyte predominant cells. Within B- and T-cell non-Hodgkin lymphomas, nuclear STAT6^YE361 was seen in: B-cell lymphoma unclassifiable with features intermediate between diffuse large B-cell lymphoma and classical Hodgkin lymphoma, and in primary mediastinal large B-cell lymphoma. Strong PD-L1 gene amplification was noted in the paired cHL and relapse B-cell lymphoma unclassifiable with features intermediate between diffuse large B-cell lymphoma and classical Hodgkin lymphoma, although STAT6^YE361 was negative in both biopsies. Whole-exome sequencing identified mutations in B2M, XPO1, and ITPKB as well CISHP213L (in the STAT pathway) in one classical Hodgkin lymphoma patient positive for nuclear STAT6^YE361 although no underlying STAT6 mutations were observed in either sample examined. STAT6^YE361 nuclear staining has 100% positive predictive value and 85.7% negative predictive value in confirming or excluding classical Hodgkin lymphoma diagnosis in the distinction from nodular lymphocyte predominant Hodgkin lymphoma and other benign and malignant entities.

Management of children and adolescents with gray zone lymphoma: A case series

BACKGROUND

Data on management of gray zone lymphoma (GZL) in children and adolescents are scarce.

PROCEDURE

This retrospective study assessed clinical characteristics and outcome in six Austrian patients with GZL less than 18 years of age (male-to-female ratio: 1:1; median age: 15.8 years).

RESULTS

Two patients each had a classical Hodgkin lymphoma (cHL)-like and composite GZL subtype, and one patient each had a large B-cell non-Hodgkin lymphoma (LBCL)-like and sequential GZL subtype. All had advanced disease with mediastinal and extranodal involvement. Five patients received an LBCL- and one patient a cHL-directed polychemotherapy ± radiotherapy. Out of the former patients, three survived, including two who relapsed and underwent high-dose chemotherapy with autologous stem cell rescue. The latter patient survived.

CONCLUSIONS

GZL remains a diagnostic and therapeutic challenge, necessitating the development of novel treatment concepts performed in a prospective setting.

GATA3 Immunohistochemical Staining in Hodgkin Lymphoma: Diagnostic Utility in Differentiating Classic Hodgkin Lymphoma From Nodular Lymphocyte Predominant Hodgkin Lymphoma and Other Mimicking Entities

BACKGROUND

Classic Hodgkin lymphoma (CHL) and nodular lymphocyte predominant Hodgkin lymphoma (NLPHL) are clinically distinct entities, with different prognostic and treatment implications. In addition, several large B-cell lymphomas and some T-cell lymphomas can mimic CHL. Differentiating these entities from CHL is crucial for ensuring appropriate therapy. GATA3 is a T-cell transcription factor involved in T-cell maturation and has been previously shown to be overexpressed in CHL cells via gene expression profiling. We investigated the utility of GATA3 immunostain in differentiating CHL from NLPHL and other mimicking entities.

MATERIALS AND METHODS

We accrued 17 NLPHLs, 49 CHLs [23 nodular sclerosis (NS), 3 syncytial variants, 3 lymphocyte rich and 13 mixed cellularity types], 4 primary mediastinal large B-cell lymphomas (PMBLs), 2 Epstein-Barr virus (EBV) positive diffuse large B-cell lymphomas (DLBCLs) (EBV+LBCLs), 2 T-cell/histiocyte-rich large B-cell lymphomas (TCHRBCLs), 1 gray zone lymphoma, and 2 tissue microarrays consisting of 72 DLBCLs. One slide from each was stained with GATA3 and percent positive tumor cells and intensity of nuclear expression was semiquantitatively graded independently by 2 board certified hematopathologists.

RESULTS

GATA3 was positive in 80% of CHLs. Both percent positivity and intensity of staining varied greatly. Syncytial variant of NS subtype showed the highest positivity rate (3/3; 100%), followed by NS (20/23; 87%), mixed cellularity (9/13; 70%), and lymphocyte rich (2/3; 67%). GATA3 was negative in all NLPHLs, EBV+LBCLs, TCRBCLs, and DLBCLs stained. The single gray zone lymphoma and 3/4 PMBLs were positive.

CONCLUSIONS

Nuclear expression of GATA3 can be used to delineate CHL from NLPHL. GATA3 positivity effectively excludes NLPHL with 100% negative predictive value. However, as 20% of CHL can be negative for GATA3, CHL cannot be ruled out with negative GATA3. Additional findings include GATA3 positivity among PMBLs, whereas all 72 DLBCLs were negative for GATA3. This finding further highlights similarities between CHL and PMBL.

Gene Expression Profiling of Mediastinal Gray Zone Lymphoma and Its Relationship to Primary Mediastinal B-cell Lymphoma and Classical Hodgkin Lymphoma

Mediastinal gray zone lymphoma (MGZL) has immunopathologic features between classical Hodgkin lymphoma (cHL) and primary mediastinal thymic B-cell lymphoma (PMBL), leading to uncertainty regarding its biological relationship to these entities. We performed gene expression profiling from patients with MGZL (20), cHL (18), and PMBL (17) and show MGZL clusters between cHL and PMBL. Expression signatures reveal germinal B-cell and IFN regulatory factor 4 (IRF4) signatures were relatively low in MGZL and cHL compared with PMBL, indicating downregulation of the B-cell program in MGZL, a hallmark of cHL. T-cell and macrophage signatures were higher in MGZL and cHL compared with PMBL, consistent with infiltrating immune cells, which are found in cHL. The NFκB signature was higher in MGZL than PMBL, and like cHL, MGZL and PMBL express NFκB inducing kinase (NIK), indicating noncanonical signaling. These findings indicate that while MGZL has distinctive clustering, it is biologically closer to cHL.

Composite and sequential lymphoma between classical Hodgkin lymphoma and primary mediastinal lymphoma/diffuse large B-cell lymphoma, a clinico-pathological series of 25 cases

Composite and sequential lymphomas involving both classical Hodgkin lymphoma (CHL) and primary mediastinal B-cell lymphoma (PMBCL) are rare phenomena. Beyond the relevant biological interest raised by these cases, treatments and outcome data are poorly covered in the recent literature. This retrospective analysis describes the pathological and clinical characteristics of 10 composite and 15 sequential cases included after a central pathological review. At diagnosis, 70% of the composite lymphomas presented a disseminated and extranodal disease. Among the 15 sequential lymphomas, 12 were CHL at first occurrence and three were PMBCL. Based on their clinical evolution, these sequential lymphomas could be divided into early (i.e., diagnosis of second lymphoma within a year) and late [(i.e., a second lymphoma occurrence occurring after a long period of complete remission]). All composite cases were alive in complete remission after a median follow-up of 34 months. If the early sequential lymphoma presented a particularly poor outcome with a median overall survival shorter than one year, the late cases were efficiently salvaged. Further molecular studies are needed to describe the underlying biology of these rare diseases, possibly representing the extreme of tumour cell plasticity found in grey-zone lymphoma.

Diagnostic utility of programmed cell death ligand 1 (clone SP142) in mediastinal composite lymphoma: A report of two cases

Composite lymphoma is a well-known diagnostic entity exhibiting the synchronous occurrence of two or more distinct types of lymphomas in the same specimen. Here we report two patients, a 14-year-old female (Case 1) and a 45-year-old male (Case 2), with mediastinal composite lymphoma, comprising nodular sclerosis classic Hodgkin lymphoma (NSCHL) and primary mediastinal large B-cell lymphoma (PMBL). Both patients had a mediastinal mass, and manifested two different histologic components in the same biopsy, one characteristic of NSCHL and the other PMBL. The NSCHL areas included Hodgkin and Reed-Sternberg (HRS) cells with typical immunophenotypic features (CD30-positive and CD20-negative), whereas the sheets of large tumor cells characteristic of PMBL were strongly and uniformly CD20-positive. Interestingly, although both cases showed neoplastic PD-L1 (nPD-L1) positivity on the HRS cells of NSCHL, they differed regarding nPD-L1 expression on the PMBL tumor cells. In Case 1, the nPD-L1-negative PMBL component was anatomically situated outside the NSCHL lesion. On the other hand, in Case 2, the nPD-L1-positive PMBL component was characterized by transitional or continuous areas with the NSCHL component. These findings suggested that nPD-L1 expression may define two subtypes of PMBL that are more similar to or distinct from classic Hodgkin lymphoma.

Primary Mediastinal Nodal and Extranodal Non-Hodgkin Lymphomas: Current Concepts, Historical Evolution, and Useful Diagnostic Approach: Part 1

Primary mediastinal non-Hodgkin lymphomas (PM-NHLs) represent ~5% of all NHLs and comprise lymphomas of B-cell and T-cell origin. PM-NHLs are defined as involvement of mediastinal lymph nodes, thymus, and/or mediastinal organs (heart, lung, pleura, pericardium) by NHL without evidence of systemic disease at presentation. The clinical scenario is variable and depends on the lymphoma subtype. The radiologic presentation is also variable ranging from a mediastinal mass with or without superior vena cava syndrome, a pleural or a cardiac mass associated with an effusion, or as an effusion only. The diagnosis of PM-NHLs can only be established by microscopic evaluation, and therefore, general pathologists should be aware of these tumors and familiar with their diagnostic approach. The most common anterior mediastinal NHLs (90% to 95%) are primary mediastinal large B-cell lymphoma and T lymphoblastic lymphoma. Thymic marginal zone lymphoma and mediastinal gray zone lymphoma are very rare. The remainder PM-NHLs involving middle or posterior mediastinum include diffuse large B-cell lymphoma (DLBCL) and rare cases of T-cell lymphoma, including anaplastic large cell lymphoma and breast implant-associated anaplastic large cell lymphoma extending to the anterior mediastinum. Primary pleural and cardiac NHLs are mostly DLBCLs. Other rare subtypes of PM-NHLs include DLBCL associated with chronic inflammation/pyothorax-associated lymphoma, fibrin-associated DLBCL (both EBV), and pleural and/or pericardial primary effusion lymphoma (HHV-8/EBV). We review the historical aspects, epidemiology, clinico-radiologic features, histopathology, immunohistochemistry, differential diagnosis, and relevant cytogenetic and molecular features of PM (thymic) LBCL, PM "nonthymic" DLBCL, BCL, unclassifiable, with features intermediate between DLBCL and classic Hodgkin lymphoma (mediastinal gray zone lymphoma), DLBCL associated with chronic inflammation (pyothorax-associated lymphoma), fibrin-associated DLBCL, and primary effusion lymphoma. This review represents the first part of 2 manuscripts covering PM-NHLs.

Challenges in the Diagnosis of Gray Zone Lymphomas

The diagnosis of B-cell lymphoma unclassifiable with features intermediate between diffuse large B-cell lymphoma and classical Hodgkin lymphoma, also called gray zone lymphoma (GZL), is frequently challenging. Incorrect diagnosis as either classic Hodgkin lymphoma or diffuse large B-cell lymphoma has significant implications for choice of upfront therapy based on recent large multi-institutional series from the United States and Europe. These studies have clarified some diagnostic challenges and provided guidance on the spectrum of morphologic features in this entity. This article clarifies some of the diagnostic conundrum surrounding GZL and provides an evidence-based approach to GZL diagnosis using morphology and immunohistochemistry.