Mediastinal gray zone lymphoma: clinico-pathological characteristics and outcomes of 99 patients from the Lymphoma Study Association

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.

Gray zone lymphoma: A case report and comprehensive review of literature

Gray zone lymphoma is a very rare liquid malignancy that possesses intersecting features between primary mediastinal B-cell lymphoma and classic Hodgkin Lymphoma. In the case presented and accompanying literature review, we will discuss a patient with a chief complaint of shortness of breath and was found to have a mediastinal mass with biopsy consistent with mediastinal gray zone lymphoma. Herein, we explore the historical and recently updated diagnostic criteria of gray zone lymphoma from 2022 as well as the pathophysiology as it pertains to gene expression, while also reviewing the histological findings, epidemiology and treatment modalities.

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.

Combined use of pathological and genomic alteration analyses for the diagnosis of gray zone lymphoma

Histiocytic sarcoma (HS) is a rare malignancy showing morphologic and immunophenotypic features of histiocytes. HS has morphologic overlap with many other diseases, including various kinds of lymphomas. Gray zone lymphoma (GZL) is a rare B-cell lymphoma subtype characterized by overlapping features between diffuse large B-cell lymphoma and classic Hodgkin lymphoma. The histologic overlap with other diverse diseases of HS and the pathological diversity of GZL make it difficult to render a diagnosis. A 44-year-old woman who was initially diagnosed with HS was diagnosed with GZL after reexamination, including a genetic alteration test. After 6 cycles of brentuximab vedotin, doxorubicin, vinblastine, and dacarbazine, she achieved a complete response. Genomic alteration assessment may be useful for the accurate diagnosis of malignant lymphomas, which are difficult to diagnose, such as GZL.

Comparative analysis of international prognostic indices in gray-zone lymphoma

Gray-zone lymphoma (GZL) reflects an aggressive B-cell neoplasm with features intermediate between diffuse large B-cell lymphoma (DLBCL) and classical Hodgkin lymphoma (cHL). The International Prognostic Index (IPI) and its derivatives (R-IPI, NCCN-IPI, and the Hasenclever IPS) have been established for DLBCL or cHL while the most suitable scoring system for GZL remains undetermined. In an exploratory multi-centric cohort of GZL (n = 61), we performed a comparative analysis of prognostic indices with regard to model fit and mutual concordance. The calculation of the corrected Akaike's information criterion (cAIC) and Harrel's concordance index (c-index) for each scoring system identified the NCCN-IPI to harbor the most convincing prognostic capabilities regarding both overall survival (OS) and progression-free survival (PFS) compared to its enhanced derivatives. The current results affirm the clinical utility of the NCCN-IPI and suggest its preferential use in clinical practice in GZL-patients.

Clinicopathological features of syncytial variant nodular sclerosis Hodgkin lymphoma

The syncytial variant of nodular sclerosis Hodgkin lymphoma (SV-NSHL) is uncommon, and its clinicopathological features have not been well analyzed. In this study, we collected 142 cases of SV-NSHL. There were 76 (53.5%) males and 66 (46.5%) females with a median age of 28 years (range, 12-78); 59.9% were younger than 30 years. Patients usually presented with a mediastinal mass (97.6%) and often with bulky (35.7%) and advanced stage disease (3 or 4) (39.7%). Follow-up showed that 61.1% of patients developed relapse after standard therapy. Morphologically, the neoplasms were composed of sheets or large clusters of pleomorphic neoplastic cells with a cohesive appearance that were frequently associated with necrosis. Neutrophils and eosinophils were frequent in the background, whereas small lymphocytes were decreased. Immunohistochemical analysis showed that the following markers were frequently positive: CD30 (100%), MUM1/IRF4 (96%), PAX5 (95%), PD-L1 (91%), and CD15 (80%). CD45 was negative in all cases. Epstein-Barr virus-encoded small RNA (EBER) was detected in 19% of cases. In this cohort, age above 30 years (P = .0430), presence of B-type symptoms (P = .0394), elevated serum lactate dehydrogenase level (P = .0004), and disease relapse (P = .0108) were associated with a poorer overall survival. In contrast, patients with EBER-positive neoplasms had a better survival (P = .0418). Compared with a control group of non-SV-NSHL patients, patients with SV-NSHL were associated with a poorer overall survival (P = .011). These data suggest that SV morphology is associated with a poorer prognosis in patients treated with traditional standard-of-care therapy for classic Hodgkin lymphoma.

DA-R-EPOCH vs R-CHOP in DLBCL: How do we choose?

The emerging molecular and prognostic characterization of diffuse large B-cell lymphoma (DLBCL) has challenged the rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) treatment paradigm in recent years, with the identification of several DLBCL subtypes associated with significantly inferior survival after standard R-CHOP therapy. Efforts to improve upon the R-CHOP backbone have included dose intensification as well as the addition of new agents; the infusional dose-adjusted rituximab, etoposide, prednisone, vincristine, cyclophosphamide, and doxorubicin (DA-R-EPOCH) regimen has been identified as a potential replacement for R-CHOP in high-risk DLBCL. In this review, we provide a historical perspective on the R-CHOP and DA-R-EPOCH regimens and summarize the clinical trial literature regarding the efficacy of each regimen in various risk groups of DLBCL. Further, we propose clinical management scenarios in which DA-R-EPOCH may be preferred, including some for patient populations in which the use of R-CHOP vs DA-R-EPOCH is controversial.

Primary mediastinal Large B-cell Lymphoma

Primary mediastinal large B-cell lymphoma (PMBCL) is a separate entity in the WHO classification based on clinico-pathologic features and a distinct molecular signature which overlaps with nodular sclerosis classical Hodgkin lymphoma (NScHL). Molecular classifiers can distinguish PMBCL from diffuse large B-cell lymphoma (DLBCL) using RNA derived from paraffin-embedded tissue and are integral to future studies. However, given that ~5% of DLBCL can have a 'molecular' PMBCL phenotype in the absence of mediastinal involvement, clinical information will remain critical for diagnosis. Studies over the last 10-20 years have elucidated the biologic hallmarks of PMBCL which are reminiscent of cHL, including the importance of JAK-STAT and NFKB signaling pathways as well as an immune evasion phenotype through multiple converging genetic aberrations. The outcome of PMBCL has improved in the modern rituximab era, however controversies remain whether there is a single standard treatment for all patients and when to integrate radiotherapy. Regardless of the frontline therapy, refractory disease can occur in up to 10% of patients and correlates with poor outcome. With emerging data supporting high efficacy of PD1 inhibitors in PMBCL, studies are underway integrating them into the up-front setting.

Mediastinal Lymphoproliferative Disorders

Lymphoproliferative disorders comprise 50% to 60% of all mediastinal malignancies in both children and adults. Primary mediastinal involvement is rare (∼5%), whereas secondary mediastinal involvement by systemic disease is more common (10% to 25%). Primary mediastinal disease is defined as involvement by a lymphoproliferative disorder of mediastinal lymph nodes, the thymus, and/or extranodal mediastinal organs without evidence of systemic disease at presentation. In this review, the clinical, radiologic, histopathologic, immunohistochemical, and genetic features of some of the most characteristic mediastinal lymphoproliferative disorders are presented. The entities discussed here include: classic Hodgkin lymphoma with emphasis on nodular sclerosis and mixed cellularity types, and non-Hodgkin lymphomas, including primary mediastinal (thymic) large B-cell lymphoma, mediastinal gray zone lymphoma, mediastinal diffuse large B-cell lymphoma, thymic marginal zone lymphoma, mediastinal plasmacytoma, T-lymphoblastic lymphoma, and anaplastic large cell lymphoma. Although not a malignant process, hyaline vascular Castleman disease is also discussed here as this disorder commonly involves the mediastinum. Despite multiple advances in hematopathology in recent decades, the day-to-day diagnosis of these lesions still requires a morphologic approach and a proper selection of immunohistochemical markers. For this reason, it is crucial for general pathologists to be familiar with these entities and their particular clinicoradiologic presentation.

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.

Syncytial variant of nodular sclerosis Hodgkin lymphoma: an under-emphasized variant

Syncytial variant nodular sclerosis Hodgkin lymphoma (HL) is a variant that was described over 40 years ago but has received relatively little attention in the literature. Earlier studies emphasized the predominance of Hodgkin (also known as lacunar) and Reed-Sternberg (HRS) cells in this variant. Here we emphasize that the HRS cells in syncytial variant nodular sclerosis HL have a cohesive appearance, form confluent sheets, and have an immunophenotype typical of classic HL. Cases of syncytial variant nodular sclerosis HL are also commonly associated with necrosis and granulocytes in the background. Patients with syncytial variant nodular sclerosis HL tend to be young adults who present with lymphadenopathy (most often cervical) and/or a mediastinal mass. The few studies of syncytial variant nodular sclerosis HL available in the literature have suggested that this variant is associated with a higher frequency of B-type symptoms and advanced-stage disease, and one study has suggested that patients have a shorter progression-free survival than patients with typical nodular sclerosis HL. However, currently patients with syncytial variant nodular sclerosis HL are treated similarly to patients with typical nodular sclerosis HL. The large number of neoplastic cells in syncytial variant nodular sclerosis HL cases presents a diagnostic challenge, and the differential diagnosis includes non-Hodgkin lymphomas, other types of classic HL, gray zone lymphoma, thymoma and metastatic neoplasms to the mediastinum including germ cell tumors, carcinomas, and melanoma.

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.

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.

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.

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.

Clinicopathological significance of CD79a expression in classic Hodgkin lymphoma

Classic Hodgkin lymphoma (CHL) is a lymphoid neoplasia characterized by the presence of large tumor cells, referred to as Hodgkin and Reed-Sternberg (HRS) cells, originating from B-cells in an inflammatory background. As the clinical significance of B-cell markers has yet to be fully elucidated, this study aimed to clarify the clinicopathological significance of CD79a in 55 patients with CHL. They were immunohistochemically divided into two groups, comprising of 20 CD79a-positive and 35 CD79a-negative patients. There was no significant correlation between CD79a and CD20 expression (rs = 0.125, P = 0.362). CD79a-positive patients were significantly older at onset (P = 0.011). There was no significant correlation between CD79a-positivity and clinical stage (P = 0.203), mediastinal involvement (P = 0.399), extranodal involvement (P = 0.749), or laboratory findings, including serum levels of lactate dehydrogenase (P = 1) and soluble interleukin-2 receptor (P = 0.251). There were significant differences in overall survival (OS) (P = 0.005) and progression-free survival (PFS) (P = 0.007) between CD79a-positive and CD79a-negative patients (5-year OS: 64.6% and 90.5%; 5-year PFS: 44.0% and 76.6%, respectively). Five patients in whom the majority (> 80%) of HRS cells expressed CD79a consisted of 4 males and 1 female aged between 52 and 81 years; 4 of them were in a limited clinical stage. We concluded that CD79a-positive CHL may have unique clinicopathological features.

Use of checkpoint inhibitors in gray zone lymphoma

Checkpoint inhibitors, cancer immunotherapies, are the new forms of treatment for gray zone lymphoma, a rare subtype that combines the characteristics of both Hodgkin and non-Hodgkin disease forms. Programmed cell death protein 1/programmed cell death ligand 1 (PD-L1/PD-1) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) modulate the immune system function. Immunological checkpoints can be stimulatory or inhibitory, and tumors can use these checkpoints to protect against immune system attacks. This is a case report of a difficult diagnosis and describes the most current treatment using checkpoint inhibitors, through the review of the clinical record of a patient diagnosed with gray area lymphoma in August 2019, using a descriptive and cross-sectional analysis of the clinical history and disease evolution. The case showed that pembrolizumab therapy is an effective treatment option for patients with rare gray zone lymphoma refractory to different lines of treatment. Both the diagnosis and treatment of gray area lymphoma remain a challenge for the medical and multiprofessional teams, and collaboration between them ensured effective treatment for the patient.

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.

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.

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.

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.

Gray Zone Lymphoma Arising in the Neck of a Teenager With a Germline Mutation in TP53

Gray zone lymphoma is an aggressive disease for which appropriate management is still debated. We report a 15-year-old girl with a cervical mass, an enlarged ipsilateral tonsil, and anemia. Both sites showed hypermetabolism on F18-FG positron emission tomography/CT. Surgical resection was diagnostic of Epstein-Barr virus-negative gray zone lymphoma cervical and tonsillar involvement. No abnormality was found in cytogenetic analysis on tumor cells. However, exome sequencing in peripheral blood DNA revealed a germline mutation in TP53. Complete response was achieved after surgery and 6 cycles of rituximab with dose-adjusted etoposide, prednisone, vincristine, cyclophosphamide, and doxorubicin regimen.

Biology and therapy of primary mediastinal B-cell lymphoma: current status and future directions

Primary mediastinal B-cell lymphoma (PMBCL) is a distinct disease closely related to classical nodular sclerosing Hodgkin lymphoma. Conventional diagnostic paradigms utilising clinical, morphological and immunophenotypical features can be challenging due to overlapping features with other B-cell lymphomas. Reliable diagnostic and prognostic biomarkers that are applicable to the conventional diagnostic laboratory are largely lacking. Nuclear factor kappa B (NF-κB) and Janus kinase/signal transducers and activators of transcription (JAK-STAT) signalling pathways are characteristically dysregulated in PMBCL and implicated in several aspects of disease pathogenesis, and the latter pathway in host immune evasion. The tumour microenvironment is manipulated by PMBCL tumours to avoid T-cell mediated destruction via strategies that include loss of tumour cell antigenicity, T-cell exhaustion and activation of suppressive T-regulatory cells. R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, prednisolone) and DA-EPOCH-R (dose-adjusted etoposide, prednisolone, vincristine, cyclophosphamide, doxorubicin, rituximab) are the most common first-line immunochemotherapy regimens. End of treatment positron emission tomography scans are the recommended imaging modality and are being evaluated to stratify patients for radiotherapy. Relapsed/refractory disease has a relatively poor outcome despite salvage immunochemotherapy and subsequent autologous stem cell transplantation. Novel therapies are therefore being developed for treatment-resistant disease, targeting aberrant cellular signalling and immune evasion.

An overview on the differential diagnostics of tumors of the anterior-superior mediastinum: the pathologist's perspective

The thymus is the main organ in the (anterior) (pre-vascular) mediastinum, playing a central role in the maintenance of both cellular and humoral immunity. The function of the thymus has been long underlooked due to its involution starting during young adulthood and unawareness regarding its immunological function. A variety of primary tumors and inflammatory/reactive/disreactive processes occur in the mediastinum and may involve the anterior-superior compartment and the thymus. Maldevelopment processes also take place in the pre-vascular compartment mediastinum. Although infective diseases do not currently represent the main processes in western countries, they may represent a diagnostic challenge in developing countries. The purpose of this review is to provide a short overview of the main thymic cellular components, their tumors, pseudotumors, in order to provide insights into their clinical setting and the features which assist pathologists in their differential diagnosis (DD). Specific differential diagnostic points are provided, both for "solid" tumors as well as for haematological malignancies, together with a morphological overview of cases of concern that occur in the anterior mediastinum. The main immunohistochemical characteristics of neoplastic/non-neoplastic pathology and updated specific references are also provided.

Diagnosis of Hodgkin lymphoma in the modern era

The Hodgkin lymphomas are a family of unique lymphoma subtypes, in which the nature of the neoplastic cell was enigmatic for many years. Much of the mystery has been solved, with all forms now considered to be of B-cell origin, in most cases of germinal centre derivation. Today we recognize Hodgkin lymphoma as an eponym that encompasses multiple entities. One of the unifying themes is the major contribution from the tumour microenvironment. Both the character of the neoplastic cells and the nature of the immune environment are critical to accurate diagnosis. Moreover, an understanding of the molecular alterations that characterize both the neoplastic cells and their microenvironment have led to therapeutic advances, targeting both neoplastic and reactive components. Other conditions may foster a similar inflammatory milieu and lead to lymphoproliferations that mimic the Hodgkin lymphomas. In this review we provide an update on the diagnostic features of the various subtypes and include additional information relevant for prognostic evaluation and investigation of potential therapeutic targets. Additionally, we also discuss those conditions that often cause confusion in diagnosis and need to be distinguished from the Hodgkin lymphomas.

Long-term complete remission following tandem autologous stem cell transplantation and consolidative radiotherapy for refractory mediastinal gray-zone lymphoma

Mediastinal gray zone lymphoma (MGZL) is a provisional entity with intermediate features between classical Hodgkin lymphoma (cHL) and diffuse large B-cell lymphoma. Outcomes for patients with MGZL are reportedly poorer than those for patients with cHL or primary mediastinal large B-cell lymphoma. Additionally, no standard management guidelines for patients with MGZL are available, primarily due to its recent identification, rarity, and challenges in diagnosis. Although recent several studies have suggested dose-adjusted EPOCH-R (etoposide, doxorubicin, vincristine, cyclophosphamide, prednisolone, and rituximab) may improve outcomes in patients with MGZL, numerous patients still suffer from relapsed/refractory MGZL, and the optimal management for such patients remains uncertain. Here, we report the first case of successful treatment of refractory MGZL by tandem high-dose chemotherapy supported by autologous stem cell transplantations (auto-SCTs) and consolidative radiotherapy (RT). To date, the patient remains in CR 33 months after the completion of RT, with no significant complications. This case suggests that tandem auto-SCTs may be a promising therapeutic option for relapsed/refractory MGZL.

Anaplastic variant of diffuse large B-cell lymphoma with hallmark cell appearance: Two cases highlighting a broad diversity in the diagnostics

The anaplastic variant of diffuse large B-cell lymphoma (A-DLBCL) is morphologically defined but remains an enigmatic disease in its clinicopathologic distinctiveness. Here, we report two cases involving Japanese women aged 59 years, both with A-DLBCL with the hallmark cell appearance and both indistinguishable from common and giant cell-rich patterns, respectively, of anaplastic lymphoma kinase (ALK)-positive anaplastic large cell lymphoma. Case 1 was immunohistochemically positive for CD20, CD79a and OCT-2 but not for the other pan-B-cell markers, CD30 and ALK. Case 2 showed CD20 and CD30 positivity for 50% and 20% of tumor cells in addition to strong expression of p53 and MYC. Both were positive for fascin without Epstein-Barr virus association. Our cases provide additional support for the earlier reports that A-DLBCL exhibits clinicopathologic features distinct from ordinal diffuse large B-cell lymphoma (DLBCL), and documented its broader morphologic diversity than previously recognized. They also shed light on the unique feature of absent expression of pan-B-cell markers except for CD20 and CD79a, suggesting that A-DLBCL may biologically mimic a gray zone or intermediate lymphoma between DLBCL and classic Hodgkin lymphoma.

Efficacy of High-Dose Therapy and Autologous Hematopoietic Cell Transplantation in Gray Zone Lymphoma: A US Multicenter Collaborative Study

High-dose therapy (HDT) and autologous hematopoietic cell transplantation (auto-HCT) has been anecdotally prescribed in gray zone lymphoma (GZL), showing encouraging efficacy. We conducted a multicenter retrospective study aimed at assessing outcomes after auto-HCT in 32 patients with GZL treated at 9 transplantation centers in the United States. The median age of patients at transplantation was 38 years (range, 18 to 70 years), and the majority were male (n = 21; 66%). The median number of lines of therapy before transplantation was 2 (range, 1 to 4). BEAM was the most commonly prescribed regimen (n = 23; 72%). The median duration of follow-up for surviving patients was 34 months (range, 1 to 106 months). Median overall survival (OS) was not reached. The 3-year progression-free survival (PFS) and OS for all patients were 69% and 78%, respectively. Three-year PFS and OS were 100% for patients who received only 1 line of therapy before auto-HCT versus 65% (PFS, P = .25) and 75% (OS, P = .39) for those receiving >1 line. The cumulative incidence of relapse/progression was 4% at 1 year post-transplantation and 31% at 3 years post-transplantation. The 3-year nonrelapse mortality was 0%. These findings suggest that HDT and auto-HCT is an effective treatment in patients with GZL. Our findings ideally require confirmation in a larger cohort of patients, preferably in the setting of large prospective multicenter randomized controlled trials. However, we acknowledge that such studies could be difficult to conduct in patients with GZL owing to the disease's rarity. Alternatively, a multicenter prospective study that includes tissue banking and a data registry is warranted to help better understand the biology and natural history of the disease.

Clinicopathologic consensus study of gray zone lymphoma with features intermediate between DLBCL and classical HL

Gray zone lymphoma (GZL) is described as sharing features with classical Hodgkin lymphoma (cHL) and diffuse large B-cell lymphoma (DLBCL). However, there remains complexity in establishing diagnosis, delineating prognosis, and determining optimum therapy. Sixty-eight cases diagnosed as GZL across 15 North American academic centers were evaluated by central pathology review to achieve consensus. Of these, only 26 (38%) were confirmed as GZL. Morphology was critical to GZL consensus diagnosis (eg, tumor cell richness); immunohistochemistry showed universal B-cell derivation, frequent CD30 expression, and rare Epstein-Barr virus (EBV) positivity (CD20⁺, 83%; PAX5⁺, 100%; BCL6⁺, 20%; MUM1⁺, 100%; CD30⁺, 92%; EBV⁺, 4%). Forty-two cases were reclassified: nodular sclerosis (NS) cHL, n = 27 (including n = 10 NS grade 2); lymphocyte predominant HL, n = 4; DLBCL, n = 4; EBV⁺ DLBCL, n = 3; primary mediastinal large BCL n = 2; lymphocyte-rich cHL and BCL-not otherwise specified, n = 1 each. GZL consensus-confirmed vs reclassified cases, respectively, more often had mediastinal disease (69% vs 41%; P = .038) and less likely more than 1 extranodal site (0% vs 25%; P = .019). With a 44-month median follow-up, 3-year progression-free survival (PFS) and overall survival for patients with confirmed GZL were 39% and 95%, respectively, vs 58% and 85%, respectively, for reclassified cases (P = .19 and P = .15, respectively). Interestingly, NS grade 2 reclassified patients had similar PFS as GZL consensus-confirmed cases. For prognostication of GZL cases, hypoalbuminemia was a negative factor (3-year PFS, 12% vs 64%; P = .01), whereas frontline cyclophosphamide, doxorubicin, vincristine, and prednisone ± rituximab (CHOP±R) was associated with improved 3-year PFS (70% vs 20%; P = .03); both factors remained significant on multivariate analysis. Altogether, accurate diagnosis of GZL remains challenging, and improved therapeutic strategies are needed.

How immunologic and genetic biomarkers impact Hodgkin lymphoma classification, diagnosis, and management: a huge potential that yet needs to be exploited

"Ne è passata di acqua sotto i ponti." It has been a long time since the diagnosis of Hodgkin lymphoma (HL) was exclusively based on the detection of typical Reed-Sternberg cells and the recognition of the characteristic morpho-histological background, as well as on the pathologist's skill. The discovery of immunologic, molecular genetic and virologic biomarkers has provided an objective contribution to the diagnosis and a scientific basis for a modern classification of HL. Recent updates have clarified the nature of the so-called nodular lymphocyte predominant HL and its link to the T-cell/histiocyte-rich large B-cell lymphomas as well as its relationship with the lymphocyte-rich subset of classical HL (CHL). Molecular virology studies assessed a role for the Epstein-Barr virus in the pathogenesis of a fraction of CHL of the general population, and virtually in all cases of CHL occurring in people infected by HIV. Finally, immunologic and genetic findings corroborated the existence of grey zone lymphomas at the edges of CHL. Overall, these advances provided additional and useful information to address the treatment of patients affected by HL.

Cytologic perspectives on neoteric B-cell lymphoproliferative disorders

The 2008 World Health Organization (WHO) classification of hematopoietic and lymphoid tissues has been recently revised, and publication of the updated 2016 version is expected soon. Given that cytopathologists are often involved in the diagnosis of primary, recurrent, and transformed lymphoproliferative disorders, knowledge of updates to the WHO lymphoma classification, including terminology, pathogenesis, ancillary techniques, and targeted therapies is necessary. Herein, we reference the last decade of cytology specific literature for seven newer B-cell disorders and provide illustrative examples of each entity from our files.

Impact of Expert Pathologic Review of Lymphoma Diagnosis: Study of Patients From the French Lymphopath Network

Purpose To prospectively assess the clinical impact of expert review of lymphoma diagnosis in France. Materials and Methods From January 2010 to December 2013, 42,145 samples from patients with newly diagnosed or suspected lymphomas were reviewed, according to the 2008 WHO classification, in real time by experts through the Lymphopath Network. Changes in diagnosis between referral and expert review were classified as major or minor according to their potential impact on patient care. Results The 42,145 reviewed samples comprised 36,920 newly diagnosed mature lymphomas, 321 precursor lymphoid neoplasms, 314 myeloid disorders, and 200 nonhematopoietic neoplasms, with 4,390 benign lesions. There were 4,352 cutaneous and 32,568 noncutaneous lymphomas. The most common mature noncutaneous lymphomas were diffuse large B-cell lymphomas (32.4%), follicular lymphomas (15.3%), classic Hodgkin lymphomas (13%), peripheral T-cell lymphomas (6.3%) of which angioimmunoblastic T-cell lymphomas (2.3%) were the most frequent, and mucosa-associated lymphoid tissue lymphomas (5.8%). A diagnostic change between referral and expert review occurred in 19.7% of patients, with an estimated impact on patient care for 17.4% of patients. This rate was significantly higher for patients sent with a provisional diagnosis seeking expert second opinion (37.8%) than for patients sent with a formal diagnosis (3.7%). The most frequent discrepancies were misclassifications in lymphoma subtype (41.3%), with 12.3% being misclassifications among small B-cell lymphoma entities. Fewer than 2% of changes were between benign and malignant lymphoid conditions. Minor changes (2.3%) mostly consisted of follicular lymphoma misgrading and diffuse large B-cell lymphoma subtype misclassification. Conclusion To our knowledge, this study provides the largest ever description of the distribution of lymphoma entities in a western country and highlights how expert review significantly contributes to a precise lymphoma diagnosis and optimal clinical management in a proportion of patients.