Mediastinal (thymic) large B-cell lymphoma: where do we stand?

Gray zone lymphoma effectively treated with cyclophosphamide, doxorubicin, vincristine, prednisolone, and rituximab chemotherapy: A case report

BACKGROUND

B-cell lymphoma, unclassifiable, with features intermediate between diffuse large B-cell lymphoma and classical Hodgkin lymphoma (BCLu-DLBCL/cHL), also referred to as gray zone lymphoma (GZL), is known to share features with cHL and DLBCL. However, GZL is often difficult to diagnose. There is no consensus regarding the optimal therapeutic regimen. Most reported cases of GZL have been in Caucasian and Hispanic individuals, and its incidence is lower in African-American and Asian populations, including the Japanese population.

CASE SUMMARY

A 69-year-old female presented at our hospital with a growing mass on the right side of her neck. An elastic, soft mass measuring 9 cm × 6 cm was palpable in the right cervical region. Laboratory analyses showed pancytopenia, increased serum lactate dehydrogenase levels, and markedly increased levels of soluble interleukin-2 receptor. Enhanced computed tomography (CT) and fluorodeoxyglucose positron emission tomography (PET)/CT revealed multiple lesions throughout her body. She was diagnosed with GZL based on the characteristic pathological findings, the immunophenotype [CD20+, PAX5+, OCT2+/BOB1 (focal+), CD30+, CD15-], and the strong positive expression of neoplastic programmed cell death protein ligand 1 (PD-L1) in her lymphoma cells. The lymphoma was stage IV according to the Lugano classification and high-risk according to the International Prognostic Index for aggressive non-Hodgkin lymphoma. The patient received cyclophosphamide, doxorubicin, vincristine, prednisolone, and rituximab (R-CHOP) chemotherapy because the tumor cells were CD20+. She has remained in complete remission for 3 years.

CONCLUSION

GZL was diagnosed based on histopathology and immunophenotyping with ancillary PD-L1 positivity. R-CHOP chemotherapy was an effective treatment.

Primary mediastinal large B cell lymphoma

Primary mediastinal large B cell lymphoma (PMBCL) is an aggressive large B cell lymphoma originating in the mediastinum, that mainly expresses B cell surface molecules, such as CD19, CD20, CD22, andCD79a. Clinically, they are characterized by rapidly increasing anterior mediastinal masses, which can cause compression of the surrounding tissues. The diagnosis of PMBCL mainly depends on the pathological features, imaging examination and clinical features. Currently, the most commonly used therapeutic regimens are R‐CHOP and R‐EPOCH. Radiotherapy is beneficial in some patients, but it can also lead to long‐term toxicity. The research and development of novel therapies are ongoing, and some studies have achieved encouraging results, including those conducted on chimeric antigen receptor‐modified T (CAR‐T) cell therapy and anti‐PD‐1 drugs. However, randomized controlled trials with larger sample sizes are still needed. Positron emission tomography‐computed tomography (PET‐CT) is mainly used to assess the curative effect after treatment and to guide the subsequent treatment strategy.

Characterization of DLBCL with a PMBL gene expression signature

Primary mediastinal large B-cell lymphoma (PMBL) is a type of aggressive B-cell lymphoma that typically affects young adults, characterized by presence of a bulky anterior mediastinal mass. Lymphomas with gene expression features of PMBL have been described in nonmediastinal sites, raising questions about how these tumors should be classified. Here, we investigated whether these nonmediastinal lymphomas are indeed PMBLs or instead represent a distinct group within diffuse large B-cell lymphoma (DLBCL). From a cohort of 325 de novo DLBCL cases, we identified tumors from patients without evidence of anterior mediastinal involvement that expressed a PMBL expression signature (nm-PMBLsig+; n = 16; 5%). A majority of these tumors expressed MAL and CD23, proteins typically observed in bona fide PMBL (bf-PMBL). Evaluation of clinical features of nm-PMBLsig+ cases revealed close associations with DLBCL, and a majority displayed a germinal center B cell-like cell of origin (GCB). In contrast to patients with bf-PMBL, patients with nm-PMBLsig+ presented at an older age and did not show pleural disease, and bone/bone marrow involvement was observed in 3 cases. However, although clinically distinct from bf-PMBL, nm-PMBLsig+ tumors resembled bf-PMBL at the molecular level, with upregulation of immune response, JAK-STAT, and NF-κB signatures. Mutational analysis revealed frequent somatic gene mutations in SOCS1, IL4R, ITPKB, and STAT6, as well as CD83 and BIRC3, with the latter genes significantly more frequently affected than in GCB DLBCL or bf-PMBL. Our data establish nm-PMBLsig+ lymphomas as a group within DLBCL with distinct phenotypic and genetic features. These findings may have implications for gene expression- and mutation-based subtyping of aggressive B-cell lymphomas and related targeted therapies.

Brentuximab vedotin in combination with rituximab, cyclophosphamide, doxorubicin, and prednisone as frontline treatment for patients with CD30-positive B-cell lymphomas

We conducted a phase I/II multicenter trial using six cycles of brentuximab vedotin (BV) in combination with rituximab, cyclophosphamide, doxorubicin, and prednisone (R-CHP) for treatment of patients with CD30-positive B-cell lymphomas. Thirty-one patients were evaluable for toxicity and 29 for efficacy including 22 with primary mediastinal B-cell lymphoma, five with diffuse large B-cell lymphoma, and two with gray zone lymphoma. There were no treatmentrelated deaths; 32% of patients had non-hematologic grade 3/4 toxicities. The overall response rate was 100% (95% confidence interval [95% CI]: 88-100) with 86% (95% CI: 68-96) of patients achieving complete response at the end of systemic treatment. Consolidative radiation following end-of-treatment response assessment was permissible and used in 52% of all patients including 59% of the patients with primary mediastinal B-cell lymphoma. With a median follow-up of 30 months, the 2- year progression-free survival and overall survival rates were 85% (95% CI: 66-94) and 100%, respectively. In the cohort with primary mediastinal B-cell lymphoma, the 2-year progression-free survival rate was 86% (95% CI: 62-95). In summary, BV-R-CHP with or without consolidative radiation is a feasible and active frontline regimen for CD30-positive Bcell lymphomas (ClinicalTrials.gov identifier: NCT01994850).

Successful Management of Primary Mediastinal Large B-cell Lymphoma during Pregnancy

We experienced a pregnant woman with superior vena cava syndrome at 15 weeks of pregnancy who was diagnosed with primary mediastinal large B-cell lymphoma and given chemotherapy. In this case, the clinical courses of both the mother and infant were favorable without any serious complications because of close multidisciplinary cooperation. Based on a retrospective review of this case, the administration of CHOP-like regimens during the second and third trimesters appears relatively safe. Because pregnancy and continuation of pregnancy are rare in patients with hematopoietic malignancies, the accumulation of detailed information is important.

Primary mediastinal large B cell lymphoma with coexisting aberrations of C-MYC and BCL-2: a case report and literature review

Primary mediastinal large B-cell lymphoma (PMLBCL) is an aggressive lymphoma characteristic with distinct clinical, morphologic, and immunophenotypic features. The rearrangements of C-MYC, BCL2 and/or BCL6 which are common in diffuse large B-cell lymphoma (DLBCL) are typically absent in PLMBCL. Here we proved a novel case of PMLBCL with concurrent rearrangements of C-MYC and BCL2. Histology showed typical pathomorphological features of PLMBCL. Fluorescent in situ hybridization (FISH) studies showed rearrangements of C-MYC and copy number variation (CNV) of BCL2 gene. It is not well known on the clinical significance of rearrangements of C-MYC and BCL2 genes in PMLBCL. The case gives evidence that cytogenetic testing is necessary for PMLBCLs to get precise clinical evaluation and appropriate treatment.

The Unsolved Puzzle of c-Rel in B Cell Lymphoma

Aberrant constitutive activation of Rel/NF-κB transcription factors is a hallmark of numerous cancers. Of the five Rel family members, c-Rel has the strongest direct links to tumorigenesis. c-Rel is the only member that can malignantly transform lymphoid cells in vitro. Furthermore, c-Rel is implicated in human B cell lymphoma through the frequent occurrence of REL gene locus gains and amplifications. In normal physiology, high c-Rel expression predominates in the hematopoietic lineage and a diverse range of stimuli can trigger enhanced expression and activation of c-Rel. Both expression and activation of c-Rel are tightly regulated on multiple levels, indicating the necessity to keep its functions under control. In this review we meta-analyze and integrate studies reporting gene locus aberrations to provide an overview on the frequency of REL gains in human B cell lymphoma subtypes, namely follicular lymphoma, diffuse large B cell lymphoma, primary mediastinal B cell lymphoma, and classical Hodgkin lymphoma. We also summarize current knowledge on c-Rel expression and protein localization in these human B cell lymphomas and discuss the co-amplification of BCL11A with REL. In addition, we highlight and illustrate key pathways of c-Rel activation and regulation with a specific focus on B cell biology.

Suppressor of cytokine signaling 1 gene mutation status as a prognostic biomarker in classical Hodgkin lymphoma

Suppressor of cytokine signaling 1 (SOCS1) mutations are among the most frequent somatic mutations in classical Hodgkin lymphoma (cHL), yet their prognostic relevance in cHL is unexplored. Here, we performed laser-capture microdissection of Hodgkin/Reed-Sternberg (HRS) cells from tumor samples in a cohort of 105 cHL patients. Full-length SOCS1 gene sequencing showed mutations in 61% of all cases (n = 64/105). Affected DNA-motifs and mutation pattern suggest that many of these SOCS1 mutations are the result of aberrant somatic hypermutation and we confirmed expression of mutant alleles at the RNA level. Contingency analysis showed no significant differences of patient-characteristics with HRS-cells containing mutant vs. wild-type SOCS1. By predicted mutational consequence, mutations can be separated into those with non-truncating point mutations (‘minor’ n = 49/64 = 77%) and those with length alteration (‘major’; n = 15/64 = 23%). Subgroups did not differ in clinicopathological characteristics; however, patients with HRS-cells that contained SOCS1 major mutations suffered from early relapse and significantly shorter overall survival (P = 0.03). The SOCS1 major status retained prognostic significance in uni-(P = 0.016) and multivariate analyses (P = 0.005). Together, our data indicate that the SOCS1 mutation type qualifies as a single-gene prognostic biomarker in cHL.

Recent Advances in Aggressive Large B-cell Lymphomas: A Comprehensive Review

Diffuse large B-cell lymphoma (DLBCL) is an aggressive disease with considerable heterogeneity reflected in the 2008 World Health Organization classification. In recent years, genome-wide assessment of genetic and epigenetic alterations has shed light upon distinct molecular subsets linked to dysregulation of specific genes or pathways. Besides fostering our knowledge regarding the molecular complexity of DLBCL types, these studies have unraveled previously unappreciated genetic lesions, which may be exploited for prognostic and therapeutic purposes. Following the last World Health Organization classification, we have witnessed the emergence of new variants of specific DLBCL entities, such as CD30 DLBCL, human immunodeficiency virus-related and age-related variants of plasmablastic lymphoma, and EBV DLBCL arising in young patients. In this review, we will present an update on the clinical, pathologic, and molecular features of DLBCL incorporating recently gained information with respect to their pathobiology and prognosis. We will emphasize the distinctive features of newly described or emerging variants and highlight advances in our understanding of entities presenting a diagnostic challenge, such as T-cell/histiocyte-rich large B-cell lmphoma and unclassifiable large B-cell lymphomas. Furthermore, we will discuss recent advances in the genomic characterization of DLBCL, as they may relate to prognostication and tailored therapeutic intervention. The information presented in this review derives from English language publications appearing in PubMed throughout December 2015. For a complete outline of this paper, please visit: http://links.lww.com/PAP/A12.

Characterization of memory B cells from thymus and its impact for DLBCL classification

The rare memory B cells in thymus (Thy) are considered the cells of origin for primary mediastinal large B-cell lymphoma. The objectives of the present study were to characterize the normal memory B-cell compartment in Thy and to support its association with primary mediastinal B-cell lymphoma. Seven paired human tissue samples from Thy and sternum bone marrow (BM) were harvested during cardiac surgery. B-cell subsets were phenotyped by Euroflow standard and fluorescence-activated cell sorting for microarray analysis on the Human Exon 1.0 ST Arrays platform. Differentially expressed genes between Thy and BM memory B cells were identified and correlated with the molecular subclasses of diffuse large B-cell lymphoma. Within Thy, 4% (median; range 2%-14%) of the CD45(+) hematopoietic cells were CD19(+) B cells, with a major fraction being CD27(+)/CD38(-) memory B cells (median 80%, range 76%-93%). The BM contained 14% (median; range 3%-27%), of which only a minor fraction (median 5%, range 2%-10%) were memory B cells. Global gene expression analysis of the memory B-cell subsets from the two compartments identified 133 genes upregulated in Thy, including AICDA, REL, STAT1, TNF family, SLAMF1, CD80, and CD86. In addition, exons 4 and 5 in the 3' end of AICDA were more highly expressed in Thy than in BM. The Thy memory B-cell gene profile was overexpressed in primary mediastinal B-cell lymphoma compared with other diffuse large B-cell lymphoma subclasses. The present study describes a Thy memory B-cell subset and its gene profile correlated with primary mediastinal B-cell lymphomas, suggesting origin from Thy memory B cells.

Primary Mediastinal Large B-cell Lymphoma Exhibiting Endobronchial Involvement

Primary mediastinal large B-cell lymphoma (PMLBCL) is one of the subtypes of diffuse large B-cell lymphoma. We experienced a rare case of PMLBCL that exhibited endobronchial involvement. A 33-year-old Japanese female with the chief complaints of epigastralgia, back pain, and nausea visited a primary care hospital. Computed tomography of the chest and abdomen demonstrated a bulky mass in the left anterior mediastinum, multiple pulmonary nodules, axillary lymph node swelling, and a pancreatic tumor. Fiberoptic bronchoscopy showed a white-tinged irregularly shaped endobronchial tumor accompanied by capillary vessel dilation in the left upper lobar bronchus. Taken together, these findings resulted in a diagnosis of PMLBCL.

Surface Light Chain Expression in Primary Mediastinal Large B-Cell Lymphomas by Multiparameter Flow Cytometry

OBJECTIVES

Primary mediastinal large B-cell lymphoma (PMLBL) is an aggressive B-cell lymphoma typically localized to the mediastinum. To date, no study has undertaken a comprehensive analysis of this entity by multiparameter flow cytometry.

METHODS

Cases of PMLBL with diagnostic flow cytometry were identified from pathology databases of Boston Children's Hospital, Brigham and Women's Hospital, and Stanford Hospital.

RESULTS

Most of these patients with PMLBL were women with a median age of 30 years who had stage 1 disease that lacked bone marrow involvement. By flow cytometry, 50% of all PMLBLs showed restricted surface immunoglobulin expression. When comparing patients with PMLBL by the absence or presence of surface light chain immunoglobulins, no differences were seen in the morphologic appearance; expression of CD23, CD30, or CD10; age at presentation; or clinical stage (P > .5 for all). In addition, both groups showed similarly good survival outcomes and were alive at last follow-up (11/14 [79%]; P = .542).

CONCLUSIONS

This multi-institutional study demonstrates that 50% of PMLBLs can present with clonal surface light chain expression and that PMLBL is more immunophenotypically diverse than previously described. Furthermore, our findings suggest that the absence or presence of surface light chains should not be used as criteria for diagnosis in this disease.

Clinicopathologic evaluation of MYC expression in primary mediastinal (thymic) large B-cell lymphoma

OBJECTIVES

Based on previous molecular studies, a small fraction of primary mediastinal (thymic) large B-cell lymphoma (PMBL) demonstrates MYC alterations. However, no studies have evaluated MYC protein expression by immunohistochemistry (IHC) with follow-up fluorescence in situ hybridization (FISH) analysis. We aim to evaluate the clinicopathologic importance of MYC IHC expression in PMBL.

METHODS

Three pathologists independently evaluated MYC IHC expression in 32 cases of PMBL for percent tumor positivity and nuclear intensity. FISH analysis for MYC rearrangement was performed on cases with high MYC IHC expression. Clinical data including treatment, follow-up, and outcome were also reviewed in a subset of cases.

RESULTS

Variable MYC protein expression by IHC was detected in 30 (94%) of 32 cases of PMBL. One-third of the positive cases (10/30) showed high MYC IHC expression of at least 30% nuclear positivity. FISH analyses for MYC rearrangement on these 10 cases were negative. Review of clinical data on a subset of cases with high and low MYC IHC expression showed no differences in clinical outcome.

CONCLUSIONS

MYC protein expression by IHC is present in most PMBLs. Increased MYC protein expression can be seen in one-third of the cases; however, it does not correlate with genetic abnormalities by FISH. There is also no significant impact of MYC protein expression on clinical outcomes.

The histological classification of diffuse large B-cell lymphomas

Diffuse large B-cell lymphomas (DLBCLs) are aggressive B-cell neoplasms with considerable clinical, biologic, and pathologic diversity, in part reflecting the functional diversity of the B-cell system and multiple pathways of transformation. In recent years, the advent of new high-throughput genomic technologies has provided new insights into the biology of DLBCL, leading to the identification of distinct molecular identities and novel pathogenetic pathways. This increasing complexity had led to an expanding number of entities in the World Health Organization classification. Using a multi-modality approach, the updated 2008 classification delineated some new subgroups, including DLBCLs associated with particular age groups or specific anatomic sites, as well as two borderline categories (tumors at the interface between classical Hodgkin lymphoma and DLBCL as well as between Burkitt lymphoma and DLBCL). This article reviews the histopathologic features of the various aggressive B-cell lymphoma subtypes included in the 2008 classification, with emphasis on some of the new entities as well as areas of diagnostic challenge.

EBV-Positive Grey Zone Lymphoma in an HIV Infected Man from Kampala, Uganda: Case Report

AIM

We describe the clinical, histopathological and immunophenotypic characteristics of an HIV-infected adult man on antiretroviral therapy who presented with an EBV-positive grey zone lymphoma.

CASE PRESENTATION

A 56-year-old HIV infected man from Uganda presented with a four month history of progressive abdominal swelling and B-symptoms. He was on highly active antiretroviral therapy (HAART) and cotrimoxazole. He was afebrile (36.9°C), severely wasted (BMI 14.8), and mildly anaemic. On physical examination, he had a 15 by 8 cm mass in the hypogastrium and umbilical region. The total white cell count was 8.3×10³/μL; neutrophils, 5.72×10³/μL; haemoglobin 11.1g/dL, platelets 528×10³/μL, LDH 197 IU/L and CD4 367/μL. Abdominal ultrasound and CT scan showed a tumour involving the mesentery, jejunum and mid ileum. At laparotomy, a biopsy was taken, fixed, processed and stained with Haematoxylin & Eosin (H & E). Histopathology demonstrated large pleomorphic cells admixed with inflammatory smaller cells, Reed-Sternberg-like cell variants and frequent abnormal mitoses. Biomarkers CD20, PAX5, CD30 were positive but ALK negative (immunohistochemistry and strong EBER positivity in situ hybridization. The patient improved on modified CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisolone) therapy.

DISCUSSION

The tumour had features intermediate between mediastinal large B cell lymphoma and classical Hodgkin lymphoma.

CONCLUSION

We present a case of EBV-positive grey zone lymphoma in an HIV-infected man on HAART therapy diagnosed and treated in a resource constrained medical setting. The histological features are unusual and represent a low incidence lymphoma that is recognized by mixed features reminiscent of Hodgkin's lymphoma and mediastinal large B-cell lymphoma.

Expression of programmed cell death 1 ligand 2 (PD-L2) is a distinguishing feature of primary mediastinal (thymic) large B-cell lymphoma and associated with PDCD1LG2 copy gain

Primary mediastinal (thymic) large B-cell lymphoma (PMBL) and diffuse large B-cell lymphoma (DLBCL) are tumors with distinct clinical and molecular characteristics that are difficult to distinguish by histopathologic and phenotypic analyses alone. Programmed cell death 1 ligand 2 (PD-L2) is a cell surface protein expressed by activated macrophages and dendritic cells that binds PD-1 on T cells to inhibit immune responses. Amplification and/or translocations involving chromosome 9p24.1, a region that includes PDCD1LG2-encoding PD-L2, is a common event in PMBL but not DLBCL and suggests that PD-L2 expression might be a distinguishing feature of PMBL. We developed an assay for the immunohistochemical detection of PD-L2 protein in fixed biopsy specimens (PD-L2 IHC), which we applied to a cohort of PMBLs and DLBCLs. For a subset of cases, we correlated the results of PD-L2 IHC with PDCD1LG2 copy number (CN) as determined by quantitative polymerase chain reaction. Twenty-three of 32 (72%) PMBLs but only 1 of 37 (3%) DLBCLs were positive by PD-L2 IHC. Among PMBLs with PDCD1LG2 CN gain, all were positive by PD-L2 IHC. One PMBL without CN gain was positive by PD-L2 IHC. When expressed in PMBL, PD-L2 was restricted to tumor cells and not detected on intratumoral macrophages. We conclude that PD-L2 protein is robustly expressed by the majority of PMBLs but only rare DLBCLs and often associated with PDCD1LG2 copy gain. PD-L2 IHC may serve as a useful ancillary test for distinguishing PMBL from DLBCL and for the rational selection of patients for therapeutic antibodies that inhibit PD-1 signaling.

Primary mediastinal lymphoma: diagnosis and treatment options

Primary mediastinal large B-cell lymphoma (PMBCL) is a unique B-cell lymphoma variant that arises from a putative thymic medulla B cell. It constitutes 2-4% of non-Hodgkin lymphomas and occurs most frequently in young females. PMBCL is characterized by a diffuse proliferation of medium-to-large B cells associated with sclerosis. Molecular analysis shows that PMBCL is a distinct entity compared to other types of diffuse large B-cell lymphomas. PMBCL is characterized by a locally invasive anterior mediastinal bulky mass. The combination of rituximab with CHOP/CHOP-like regimens followed by mediastinal radiation therapy (RT) is associated with a 5-year progression-free survival of 75-85%. However, the role of consolidation RT still remains uncertain. More intensive regimens, such as DA-EPOCH-R without mediastinal RT, have shown very promising results. The conclusive role of PET-CT scan requires prospective studies and there is hope that this may allow to de-escalate RT and accordingly yield reliable prognostic information.

Malignant hematopoietic cell lines: in vitro models for the study of primary mediastinal B-cell lymphomas

Primary mediastinal B-cell lymphoma (PMBL) is a highly aggressive disease with a unique set of biological, clinical, morphological, immunological and in particular genetic features that in the molecular era of defining lymphomas clearly distinguishes it as a separate entity from other diffuse large B-cell lymphomas (DLBCL). A precise molecular diagnosis of PMBL can be achieved by gene expression profiling. The signature gene expression profile of PMBL is more closely related to classic Hodgkin lymphoma (cHL) than to other DLBCL subgroups. A number of common genetic aberrations in PMBL and cHL further underscore their close relationship. To investigate the pathobiology of lymphomas in depth, many groups have turned to cell lines that are suitable models facilitating molecular studies and providing unique insights. For the purposes of the current perspective, we focus on four bona fide PMBL-derived cell lines (FARAGE, KARPAS-1106, MEDB-1, U-2940) that we identified and validated as such through hierarchical cluster analysis among a large collection of leukemia-lymphoma cell lines. These gene expression profiles showed that the four PMBL cell lines represent a distinct entity and are most similar to cHL cell lines, confirming derivation from a related cell type. A validated cell line resource for PMBL should assist those seeking druggable targets in this entity. This review aims to provide a comprehensive overview of the currently available cellular models for the study of PMBL.

The truncate mutation of Notch2 enhances cell proliferation through activating the NF-κB signal pathway in the diffuse large B-cell lymphomas

The Notch2 is a critical membrane receptor for B-cell functions, and also displays various biological roles in lymphoma pathogenesis. In this article, we reported that 3 of 69 (4.3%) diffuse large B-cell lymphomas (DLBCLs) exhibited a truncate NOTCH2 mutation at the nucleotide 7605 (G/A) in the cDNA sequence, which led to partial deletion of the C-terminal of PEST (proline-, glutamic acid-, serine- and threonine-rich) domain. The truncate Notch2 activated both the Notch2 and the NF-κB signals and promoted the proliferation of B-cell lymphoma cell lines, including DLBCL and Burkitt's lymphoma cell lines. Moreover, the ectopic proliferation was completely inhibited by ammonium pyrrolidinedithiocarbamate (PDTC), an NF-κB inhibitor. Simultaneously, PDTC also reduced the expression level of Notch2. Based on these results, we conclude that the Notch2 receptor with PEST domain truncation enhances cell proliferation which may be associated with the activation of the Notch2 and the NF-κB signaling. Our results are expected to provide a possible target for new DLBCL therapies by suppressing the Notch2 and the NF-κB signaling.

Prognostic significance of pleural or pericardial effusion and the implication of optimal treatment in primary mediastinal large B-cell lymphoma: a multicenter retrospective study in Japan

The prognosis of patients with primary mediastinal large B-cell lymphoma has improved over recent years. However, the optimal treatment strategy including the role of radiotherapy remains unknown. We retrospectively analyzed the clinical outcomes of 345 patients with newly diagnosed primary mediastinal large B-cell lymphoma in Japan. With a median follow up of 48 months, the overall survival at four years for patients treated with R-CHOP (n=187), CHOP (n=44), DA-EPOCH-R (n=9), 2(nd)- or 3(rd)-generation regimens, and chemotherapy followed by autologous stem cell transplantation were 90%, 67%, 100%, 91% and 92%, respectively. Focusing on patients treated with R-CHOP, a higher International Prognostic Index score and the presence of pleural or pericardial effusion were identified as adverse prognostic factors for overall survival in patients treated with R-CHOP without consolidative radiotherapy (IPI: hazard ratio 4.23, 95% confidence interval 1.48-12.13, P=0.007; effusion: hazard ratio 4.93, 95% confidence interval 1.37-17.69, P=0.015). Combined with the International Prognostic Index score and the presence of pleural or pericardial effusion for the stratification of patients treated with R-CHOP without radiotherapy, patients with lower International Prognostic Index score and the absence of effusion comprised approximately one-half of these patients and could be identified as curable patients (95% overall survival at 4 years). The DA-EPOCH-R regimen might overcome the effect of these adverse prognostic factors. Our simple indicators of International Prognostic Index score and the presence of pleural or pericardial effusion could stratify patients with primary mediastinal large B-cell lymphoma and help guide selection of treatment.

Prognostic significance of immunophenotypes and a nodular pattern in primary mediastinal large B-cell lymphoma

To investigate the clinicopathological and prognostic significance of a nodular pattern and immunophenotypes in primary mediastinal large B-cell lymphoma (PMBL), histopathological features, including a nodular pattern and immunophenotypes, were analyzed in 58 Japanese PMBL patients. The patients were 23 men and 35 women with a median age of 31 years. The 4-year progression free survival (PFS) rate was 78%, and the 4-year overall survival (OS) rate was 89%. Among the histopathological and immunohistochemical features, Bcl6(+) (P = 0.013), MUM1(+) (P = 0.091), and pale cytoplasm (P = 0.064) were favorable prognostic indicators of PFS, and Bcl6(+) (P = 0.051) and MUM1(+) (P = 0.07) were favorable prognostic indicators of OS. Patients with Bcl2 negativity (n = 11) had 4-year PFS and OS rates of 100%. Histologically, a nodular pattern, resembling nodular sclerosis classical Hodgkin lymphoma (CHL), was observed in 22 patients (38%). However, this was not a significant prognostic indicator. In conclusion, Bcl6(+) , MUM1(+) , Bcl2(-) , and pale cytoplasm are candidate favorable prognostic indicators for PMBL and should be further examined in larger studies. We suggest that PMBL with a nodular pattern may belong to the same histological spectrum as nodular sclerosis CHL.

SOCS1 mutation subtypes predict divergent outcomes in diffuse large B-Cell lymphoma (DLBCL) patients

Suppressor of cytokine signaling 1 (SOCS1) is frequently mutated in primary mediastinal and diffuse large B-cell lymphomas (DLBCL). Currently, the prognostic relevance of these mutations in DLBCL is unknown. To evaluate the value of the SOCS1 mutation status as a prognostic biomarker in DLBCL patients, we performed full-length SOCS1 sequencing in tumors of 154 comprehensively characterized DLBCL patients. We identified 90 SOCS1 mutations in 16% of lymphomas. With respect to molecular consequences of mutations, we defined two distinct subtypes: those with truncating (major) and those with non-truncating mutations (minor), respectively. The SOCS1 mutated subgroup or the minor/major subtypes cannot be predicted on clinical grounds; however, assignment of four established gene-expression profile-based classifiers revealed significant associations of SOCS1 major cases with germinal center and specific pathway activation pattern signatures. Above all, SOCS1 major cases have an excellent overall survival, even better than the GCB-like subgroup. SOCS1 minor cases had a dismal survival, even worse than the ABC gene signature group. The SOCS1 mutation subsets retained prognostic significance in uni- and multivariate analyses. Together our data indicate that assessment of the SOCS1 mutation status is a single gene prognostic biomarker in DLBCL.

[Lymph node pathology - an update]

Immune suppression is a risk factor for malignant lymphoma development. Progress in medical science has increased the numbers of immunosuppressed patients due to organ transplantations or successful treatment of autoimmune diseases. Different forms of immune suppression and the respective lymphoma entities are discussed in this article. Another issue treated are gray zone lymphomas between Hodgkin's lymphoma and diffuse large B cell lymphoma. This category not only represents a diagnostic challenge but also represents more a true biological continuum.

Thymic neoplasm: a rare disease with a complex clinical presentation

Thymic neoplasms constitute a broad category of rare lesions with a wide spectrum of pathologic characteristics and clinical presentations which therefore require a high index of suspicion to diagnose. The natural history of the disease is seldom predictable, anywhere from an indolent to an aggressively malignant course. Although the classification and staging of these lesions are complex and controversial, complete radical surgical resection remains the gold standard of therapy. Radiation and chemotherapy are important elements of the multimodality approach to treating these patients and it is important for thoracic surgeons to work closely with their colleagues in other disciplines in the management of and future research endeavors in thymic neoplasm. In this review, we discuss the evaluation of the patient with an anterior mediastinal mass, the classification and staging of thymic neoplasms, the role of surgery, radiation and chemotherapy in treating this disease, as well as future directions in research for novel targeted therapies.

The histological and biological spectrum of diffuse large B-cell lymphoma in the World Health Organization classification

Diffuse large B-cell lymphomas (DLBCLs) are aggressive B-cell lymphomas that are clinically, pathologically, and genetically diverse, in part reflecting the functional diversity of the B-cell system. The focus in recent years has been toward incorporation of clinical features, morphology, immunohistochemistry, and ever evolving genetic data into the classification scheme. The 2008 World Health Organization classification reflects this complexity with the addition of several new entities and variants. The discovery of distinct subtypes by gene expression profiling heralded a new era with a focus on pathways of transformation as well as a promise of more targeted therapies, directed at specific pathways. Some DLBCLs exhibit unique clinical characteristics with a predilection for specific anatomic sites; the anatomic site often reflects underlying biological distinctions. Recently, the spectrum of Epstein-Barr virus (EBV)-driven B-cell proliferations in patients without iatrogenic or congenital immunosuppression has been better characterized; most of these occur in patients of advanced age and include Epstein-Barr virus (EBV)-positive large B-cell lymphoma of the elderly. Human herpesvirus 8 is involved in the pathogenesis of primary effusion lymphoma, which can present as a "solid variant." Two borderline categories were created; one deals with tumors at the interface between classic Hodgkin lymphoma and DLBCL. The second confronts the interface between Burkitt lymphoma and DLBCL, so-called "B-cell lymphoma, unclassifiable, with features intermediate between DLBCL and Burkitt lymphoma" in the 2008 classification. Most cases harbor both MYC and BCL2 translocations and are highly aggressive. Another interesting entity is anaplastic lymphoma kinase-positive DLBCL, which renders itself potentially targetable by anaplastic lymphoma kinase inhibitors. Ongoing investigations at the genomic level, with both exome and whole-genome sequencing, are sure to reveal new pathways of transformation in the future.

Non-Hodgkin lymphoma and GIST: molecular pathways and clinical expressions

We report the case of a 64-year-old woman with a gastrointestinal stromal tumor and a diffuse large cell lymphoma. For this case, we conducted a literature review in an attempt to correlate these two neoplasms on a molecular basis. Diffuse large cell lymphoma is a subtype of non-Hodgkin lymphomas. The etiologic factor of these lymphomas is considered to be the mutations or allelic losses of the TP53 tumor suppressor gene and the overexpression of the bcl-2 oncogene. Gastrointestinal stromal tumors are mesenchymal tumors, which are typically defined by the expression of c-KIT (CD117) and CD34 genes in the tumor cells. Although there are references to dispersants in the literature about patients with both non-Hodgkin lymphoma and gastrointestinal stromal tumors, there is no common molecular pathway between these two diseases. In conclusion, there is no indication that these two neoplasms are relevant on a molecular basis.

Grey zone lymphomas: lymphomas with intermediate features

The current classification of lymphoid neoplasms is based on clinical information, morphology, immunophenotype, and molecular genetic characteristics. Despite technical and scientific progress, some aggressive B-cell lymphomas with features overlapping between two different types of lymphomas remain difficult to classify. The updated 2008 World Health Organization (WHO) classification of Tumours of the Hematopoietic and Lymphoid Tissues has addressed this problem by creation of two new provisional categories of B-cell lymphomas, unclassifiable; one with features intermediate between diffuse large B-cell lymphoma and classical Hodgkin lymphoma and the second with features intermediate between diffuse large B-cell lymphoma and Burkitt lymphoma. We review here the diagnostic criteria of these two provisional entities and discuss new scientific findings in light of the 2008 WHO classification.

Primary mediastinal DLBCL: evolving biologic understanding and therapeutic strategies

Primary mediastinal diffuse large B-cell lymphoma is a quite rare clinicopathologic entity. Molecular analysis shows it to be distinct from other types of diffuse large B-cell lymphoma, and some retrospective analyses suggests that it may respond better to third-generation chemotherapy regimens than to the more commonly used CHOP. The addition of rituximab could reduce these differences; the role of consolidation with local radiotherapy, which is often used to treat residual mediastinal masses, remains. The real role of FDG-PET scanning requires prospective studies, and it is hoped that this may allow the de-escalation of radiation therapy accordingly to yield reliable prognostic information.

Molecular pathogenesis of diffuse large B-cell lymphoma

In past years, substantial insight regarding the pathogenesis of diffuse large B-cell lymphoma has been obtained. Particularly, based on gene expression profile analysis, this disease can be classified into distinct phenotypic subgroups and specific transcriptional programs have been identified. New technologies like next-generation whole genome/exome sequencing and genome-wide single nucleotide polymorphism array analysis have revealed novel lesions involved in the pathogenesis of this disease. This review focuses on the diversity of genetic lesions identified in the different subtypes of diffuse large B-cell lymphoma.

Chemotherapeutic resistance: surviving stressful situations

Chemotherapeutic regimens involve the systemic administration of genotoxic compounds that induce cancer cell death via well-established DNA damage response signaling networks. Less understood is how the treatment of other cell types within the tumor microenvironment affects the therapeutic response. Here we discuss recent work that shows that tumor-adjacent cells can respond to genotoxic stress by activating a paracrine secretory program. Although this secretory response serves to protect progenitor cells and promote tissue regeneration in conditions of cellular stress, it can also be coopted by tumor cells to survive frontline chemotherapy. Thus, local prosurvival signaling may present a fundamental barrier to tumor clearance by genotoxic agents, suggesting that effective treatments need to target both cancer cells and the tumor microenvironment.

The molecular pathogenesis of primary mediastinal large B-cell lymphoma

Primary mediastinal large B-cell lymphoma (PMBCL) is a recognized non-Hodgkin lymphoma entity with unique pathologic, clinical, and molecular characteristics distinct from those of other diffuse large B-cell lymphomas. Immunohistochemical characterization and molecular studies strongly suggest that PMBCL is of germinal center or postgerminal center origin. Pivotal gene expression profiling work defined major deregulated pathway activities that overlap with Hodgkin lymphoma and prompted a more detailed analysis of candidate genes. In particular, the nuclear factor-κB and the Janus Kinase-Signal Transducer and Activator of Transcription signaling pathways are targeted by multiple genomic hits, and constitutive activity of both pathways can be considered molecular hallmark alterations of PMBCL. Moreover, data are emerging giving unique insight into remodeling of the epigenome that affects transcriptional regulation of a multitude of genes. More recently, the tumor microenvironment of PMBCL has shifted into focus based on a number of gene perturbations altering expression of surface molecules that contribute to immune escape. These findings highlight the importance of immune privilege in the pathogenesis of PMBCL and suggest that disrupting crosstalk between the tumor cells and the microenvironment might be a rational new therapeutic target in conjunction with traditional treatment strategies.

Primary mediastinal (thymic) large B-cell lymphoma: a short review with brief discussion of mediastinal gray zone lymphoma

Primary mediastinal (thymic) large B-cell lymphoma (PMBCL) is a subtype of diffuse large B-cell lymphoma (DLBCL). It commonly presents as a bulky lesion in the anterior-superior mediastinum with symptoms related to local invasion or compression. Microscopic examination typically shows infiltration of medium-large cells surrounded by collagen fibrosis. The neoplastic cells express B-cell markers, and CD30 often shows heterogeneous staining. Comparative genomic hybridization has identified gains in loci of 9p24 and 2p15 as well as Xp11.4-21 and Xq24-26. Amplification of REL and BCL11A at 2p as well as elevated expression of JAK2, PDL1, and PDL2 at 9p has been demonstrated. Nodular sclerosis classic Hodgkin lymphoma needs to be differentiated from PMBCL and cases with overlapped features have been described as mediastinal gray zone lymphoma. Primary mediastinal (thymic) large B-cell lymphoma carries a favorable prognosis in comparison to conventional DLBCL.

Aggressive B-cell lymphomas: a review of new and old entities in the WHO classification

Aggressive B-cell lymphomas are clinically and pathologically diverse and reflect multiple pathways of transformation. The 2008 World Health Organization (WHO) classification reflects this complexity with the addition of several new entities and variants. Whereas MYC translocations have long been associated with Burkitt lymphoma (BL), deregulation of MYC has been shown to occur in other aggressive B-cell lymphomas, most often as a secondary event. Lymphomas with translocations of both MYC and BCL2 are highly aggressive tumors, with a high failure rate with most treatment protocols. These "double-hit" lymphomas are now separately delineated in the WHO classification as B-cell lymphoma, unclassifiable, with features intermediate between diffuse large B-cell lymphoma (DLBCL) and BL. A MYC translocation is also found uncommonly in DLBCL, but the clinical consequences of this in the absence of a double hit are not yet fully delineated. Most recently, MYC translocations have been identified as a common secondary event in plasma cell neoplasms, seen in approximately 50% of plasmablastic lymphoma. Another area that has received recent attention is the spectrum of EBV-driven B-cell proliferations in patients without iatrogenic or congenital immunosuppression; most of these occur in patients of advanced age and include the EBV-positive large B-cell lymphomas of the elderly.

Gene arrays in lymphoma: Where will they fit in?

Molecular diagnostics for lymphoid malignancies has undergone substantial technical evolution during the past two decades, moving from labor-intensive investigations of individual abnormalities to high-throughput genome-wide analyses. Accordingly, its role has expanded to new fields such as monitoring of minimal residual disease and, more recently, outcome prediction in specific lymphoma subtypes. One novel technology that has had a major impact on the molecular diagnosis of lymphoid malignancies is gene expression profiling by DNA microarrays. It has provided robust and distinct molecular signatures for the most common types of lymphomas and has identified novel subsets that would not be identified by conventional methods. It also has led to the construction of molecularly defined prognostic models in these lymphoma subtypes and to a better understanding of the molecular mechanisms of lymphomagenesis. This development will undoubtedly transform diagnostic medicine in the near future and lead us into an era when tumor diagnosis will incorporate the information of critical molecular abnormalities that will have significant impact on disease outcome in each individual tumor sample. Future treatments are likely to be founded on effective, individualized, and mechanism-based therapies with the least toxicity.

[Primary mediastinal large B-cell lymphoma: histopathologic features. A specific tumour]

The diffuse large B-cell lymphomas of the mediastinum were long considered to be a variant of the classic forms of large B-cell lymphomas. However, their clinical and radiological features and especially their histopathological variants point to other lymphoid tumours such as Hodgkin's disease or anaplastic lymphomas, thymic tumours, germ cell tumours or metastatic tumors. The immunohistochemical findings are of prime importance in the diagnosis. This has recently been completed by molecular studies. Currently, they represent a distinct entity among the large B-cell lymphomas, due to their clinical, pathological and molecular features as well as the outcome. The authors report a new case in a young man.

Primary mediastinal (thymic) large B cell lymphoma with aberrant expression of CD3: a case report with review of the literature

We report the first case of primary mediastinal large B cell lymphoma (PMBL) with aberrant expression of CD3. PMBL is a subtype of diffuse large B cell lymphoma (DLBCL) and usually presents with bulky mediastinal lesions. Lineage ambiguity/infidelity is uncommon in DLBCL but has been described in sporadic case reports/series. A literature search identifies 13 additional cases of DLBCL expressing CD3, with the majority displaying cytoplasmic expression. Of the 14 total cases, 6 are pyothorax-associated lymphoma, 4 are conventional DLBCL, 2 are plasmablastic lymphoma, one is primary effusion lymphoma and one is PMBL. Two cases show genotypic ambiguity/infidelity with dual clonal IG and TCR gene rearrangements in addition to ambiguous immunophenotypes. Of the 13 cases tested for EBV status, 11 are positive, suggesting an important role of EBV in promoting lineage ambiguity/infidelity. A low threshold for testing EBV status is advocated in DLBCL with phenotypic ambiguity along with panels of immunohistochemical and molecular studies.

[Grayzone lymphoma. Clinical relevance]

Malignant lymphomas are classified into different entities according to their morphology, immunohistochemical parameters and clinical behavior. Several important pathogenetic events can be assigned to certain lymphoma entity types. Nevertheless, some cases present overlapping morphologic and immunohistochemical characteristics and a clear-cut diagnosis cannot be made. This is particularly the case with aggressive lymphomas for which a clear distinction cannot be made between the entities of diffuse large cell lymphoma/Burkitt lymphoma or primary mediastinal B cell lymphoma/classic Hodgkin's lymphoma. In order to redress this situation, two new gray zone entities were introduced in the WHO 2008 classification. Until further knowledge regarding the therapy, behavior and prognosis of these gray zone lymphomas has been gained, they should continue to be considered as distinct entities.

No evidence for the JAK2 (V617F) or JAK2 exon 12 mutations in primary mediastinal large B-cell lymphoma

Dysregulated JAK2 signaling has been shown to play a significant role in the pathogenesis of myeloproliferative disorders. Recently, our work comparing gene expression signatures of primary mediastinal large B-cell lymphomas (PMLBCL) versus nodal diffuse large B-cell lymphomas revealed a relative increase in JAK2 transcripts in the former, suggesting a role for increased JAK2 signaling in a subset of these tumors. Given the likelihood of increased JAK2 signaling in PMLBCL, we sought to determine whether JAK2 activating mutations were an alternative mechanism for increased JAK2 signaling in untreated PMLBCLs. We performed amplification refractory mutation analysis for the JAK2 (V617F) mutation and bidirectional sequencing for the recently described JAK2 exon 12 mutations on genomic DNA isolated from a well-characterized cohort of PMLBCLs. No evidence of the mutant JAK2 (V617F) allele or JAK2 exon 12 mutations was detected in 31 PMLBCL cases tested. Analysis using cell lines derived from PMLBCLs (n = 1) and from the molecularly similar classic Hodgkin lymphoma (n = 4) also failed to reveal involvement of a mutant JAK2 allele. Taken together, these results suggest that JAK2 signaling in PMLBCLs occurs by mechanisms distinct from JAK2 (V617F) or JAK2 exon 12 activating mutations.

Mutational Analysis of IgVH and BCL-6 Genes Suggests Thymic B-cells Origin of Mediastinal (Thymic) B-cell Lymphoma

Mediastinal (thymic) large B-cell lymphoma (MBL) has been defined as a subtype of diffuse large B-cell lymphoma (DLBL) arising in the mediastinum with characteristic clinicopathological features. It has been postulated that MBL arise from non-circulating thymic B-cells and represent a distinct lymphoma entity, however, the histogenesis of the disease is not yet fully understood. In order to clarify the histogenetic derivation of MBL and to determine the relationship of MBL to thymic B-cells we have analyzed the nucleic acid sequences of immunoglobulin (Ig) heavy chain variable region (VH) and 5' noncoding region of BCL-6 genes in normal thymic B-cells and six cases of MBL. Thymic B-cells and tumor cells of MBLs displayed hypermutated VH and/or BCL-6 genes but intraclonal divergence did not associate with these mutations. Since somatic mutations of the IgVH and BCL-6 genes are histogenetic markers of B-cell transit through the germinal centre (GC), these results suggest that both thymic B-cells and MBLs derived from GC or an equivalent environment where B-cells underwent somatic hypermutation. The similar pattern of mutations of IgVH and BCL-6 genes found in thymic B-cells and MBLs further supports the theory that MBLs originate from thymic B-cells.

Recurrent mutations of the STAT6 DNA binding domain in primary mediastinal B-cell lymphoma

Primary mediastinal B-cell lymphoma (PMBL) is a separate entity of aggressive B-cell lymphoma, characterized by a constitutive activation of janus kinase-signal transducer and activator of transcription (JAK-STAT) signaling pathway, also observed in Hodgkin lymphoma. Although many cancers exhibit constitutive JAK-STAT pathway activation, mutations of STAT genes have not been reported in neoplasms. Here, we show that MedB-1 PMBL-derived and L1236 Hodgkin-derived cell lines and 20 of 55 (36%) PMBL cases harbor heterozygous missense mutations in STAT6 DNA binding domain, whereas no mutation was found in 25 diffuse large B-cell lymphoma samples. In 3 cases, somatic origin was indicated by the absence of the mutations in the nontumoral tissue. The pattern of STAT6 mutations was different from the classical features of somatic hypermutations. The mutant STAT6 proteins showed a decreased DNA binding ability in transfected HEK cells, but no decrease in expression of STAT6 canonical target genes was observed in PMBL cases with a mutated STAT6 gene. Although the oncogenic properties of STAT6 mutant proteins remain to be determined, their recurrent selection in PMBL strongly argues for their involvement in the pathogenesis of this aggressive B-cell lymphoma.

Treatment of primary mediastinal large B cell lymphoma with an alternating chemotherapy regimen based on high-dose methotrexate

Primary mediastinal large B cell lymphomas (MLCL) differ from other diffuse large cell lymphomas, leading to a description as a separate entity in the current World Health Organization classification. Dose intensification improves long-term results, but no standard therapy has been established so far. We investigated the use of a high-dose methotrexate-based alternating chemotherapy regimen (B-ALL protocol of the German ALL study group) followed by consolidative mediastinal radiotherapy first as a single-center trial, then later as a prospective multicenter trial in 44 patients with a median age of 33 years. Response rates exceeded 90% with an overall survival rate of 80% in the single-center group (8.6 years median follow-up) and 82% in the multicenter group (2.5 years follow-up).Short-term toxicity was manageable, but required hospitalization: the rates of grade 3 or 4 toxicity were 20% (for mucositis), 42% (for neutropenia), 29% (for thrombocytopenia), and 9% (for neutropenic fever). No relapse occurred more than 2 years after diagnosis and initiation of treatment, but unfortunately, no patient with overt progression or relapse within these 2 years could be salvaged. Future directions in the treatment of MLCL will not focus on further dose intensification, but rather on the incorporation of (radio)immunotherapy as a therapeutic tool and gene expression profiling as well as positron emission tomography-computed tomography as stratifying tools.