Efficacy and safety of geptanolimab (GB226) for relapsed/refractory primary mediastinal large B-cell lymphoma: an open-label phase II study (Gxplore-003)

BACKGROUND

This study aimed to assess the efficacy and safety of geptanolimab (GB226), a fully humanized, recombinant anti-programmed cell death-1 monoclonal antibody, in Chinese patients with refractory or relapsed (r/r) primary mediastinal large B-cell lymphoma (PMBCL).

METHODS

This was a multicenter, open-label, single-arm phase II study (Gxplore-003), conducted at 43 hospitals in China (NCT03639181). Patients received geptanolimab intravenously at a dose of 3 mg/kg every 2 weeks until documented confirmed disease progression, intolerable toxicity, or any other cessation criteria was met. The primary endpoint was objective response rate (ORR) in the full analysis set assessed by the independent review committee (IRC) according to the Lugano Classification 2014.

RESULTS

This study was prematurely terminated due to the slow rate of patient accrual. Between Oct 15th, 2018 and Oct 7th, 2020, 25 patients were enrolled and treated. By the data cutoff date on Dec 23rd, 2020, the IRC-assessed ORR was 68.0% (17/25; 95% confidence interval [CI] 46.5-85.1%), with the complete response rate of 24%. The disease control rate was 88% (22/25; 95%CI 68.8-97.5%). Median duration of response was not reached (NR) (95%CI, 5.62 months to NR), with 79.5% of patients having response durations of more than 12 months. Median progression-free survival was NR (95%CI, 6.83 months to NR). Treatment-related adverse events (TRAEs) were reported in 20 of 25 (80.0%) patients, and grade 3 or higher TRAEs occurred in 11 of 25 (44%) patients. No treatment-related deaths occurred. The immune-related adverse events (irAEs) of any grade were observed in 6 (24.0%) patients, and no grade 4 or grade 5 irAEs were reported.

CONCLUSION

Geptanolimab (GB226) demonstrated promising efficacy and a manageable safety profile in Chinese patients with r/r PMBCL.

Genetic Factors in Familial Manifestation of Primary Mediastinal Large B-Cell Lymphoma over Two Generations

INTRODUCTION

Primary mediastinal large B-cell lymphoma (PMBL) is a rarely occurring lymphoid malignancy which typically affects young adults and presents itself as an anterior mediastinal mass. Gene expression profiling as well as somatic genetic analysis revealed that it is closely related to classical Hodgkin lymphoma, whereas morphologically, it tends to resemble diffuse large B-cell lymphoma. Familial clustering of PMBL is rare - only two reports have been published to date. While it is generally accepted that positive family history is associated with increased risk of developing a lymphoma, genetic risk factors which might predispose to PMBL are largely unknown.

CASE PRESENTATION

We performed germline and tumor genetic analyses by whole-exome sequencing and array-CGH of a family, in which the father and the son both developed a PMBL. Germline investigations of both affected patients and of their two unaffected family members have not been able to provide a single risk factor associated with lymphoma predisposition. In addition, genes that were previously implicated in increased risk for PMBL, namely MLL (KMT2A) and TIRAP, were found to be intact in all investigated family members. Somatic genetic investigations identified known as well as novel genetic aberrations in tumors of the affected subjects.

CONCLUSION

We conclude that predisposition to a PMBL might be inherited through a combination of low- or moderate-risk factors and provide a shortlist of the most likely selected candidates, which can be used in future studies.

Hodgkin Lymphoma and Its Differential Diagnosis: New Twists on an Old Challenge

Hodgkin lymphoma is a B-cell neoplasm that typically presents with localized, nodal disease. Tissues are characterized by few large neoplastic cells, usually comprising less than 10% of tissue cellularity, present in a background of abundant nonneoplastic inflammatory cells. This inflammatory microenvironment, although key to the pathogenesis, can make diagnosis a challenge because reactive conditions, lymphoproliferative diseases, and other lymphoid neoplasms may mimic Hodgkin lymphoma and vice versa. This review provides an overview of the classification of Hodgkin lymphoma, its differential diagnosis, including emerging and recently recognized entities, and strategies to resolve challenging dilemmas and avoid diagnostic pitfalls.

PD-L1+ macrophages are associated with favorable features in primary mediastinal (thymic) large B-cell lymphoma

Primary mediastinal (thymic) large B-cell lymphoma (PMBCL) is a rare, aggressive subtype of non-Hodgkin lymphoma and has a complex inflammatory microenvironment. Although most patients can be cured with standard-of-care immunochemotherapy, patients who have disease relapse have an unfavorable prognosis. Pre-treatment prognostic biomarkers in PMBCL are needed. In this retrospective study, we analyzed the clinical features and outcomes of PMBCL patients and their association with immune cell subpopulations identified by multiplex immunofluorescence at initial diagnosis. Two different antibody panels were used to assess macrophages in tissue biopsy specimens collected before the initiation of induction therapy. Twelve PMBCL patients, including five patients who had disease relapse, were included in the analysis. At a median follow-up time of 32.2 months, the median progression-free and overall survival durations were not reached. Our findings suggest that a high density of PD-L1⁺ macrophages is associated with favorable features, such as early disease stage and the absence of B-symptoms, and indicate that a high percentage of PD-L1⁺ macrophages and high densities of CD30⁺PD-L1⁺ cells and CD30⁺ cells might be associated with a lower risk of relapse within 12 months of therapy initiation. Further studies are needed to develop a biomarker signature predictive of treatment response with therapeutic consequences for patients with newly diagnosed PMBCL.

[Primary mediastinal large B-cell lymphoma, spindle cell variant demonstrating atypical image findings]

The patient was a 40-year-old woman referred to our hospital after an anterior mediastinal tumor was detected. Imaging findings revealed a tumor with irregular margins and a marked tendency to infiltrate, with some calcification. Rather than malignant lymphoma, thymic carcinoma or high-grade invasive thymoma was suspected. Endobronchial ultrasound-guided transbronchial needle aspiration biopsy and computed tomography-guided needle biopsy were performed, but no diagnosis was made. Mediastinal tumor biopsy by video-assisted thoracic surgery led to the diagnosis of primary mediastinal large B-cell lymphoma, spindle cell variant. A retrospective examination of the needle biopsy specimens revealed that some tissues considered to have been crushed were composed of spindle-shaped lymphoma cells. This study indicates that it is crucial to note that there is a subtype of primary mediastinal large B-cell lymphoma with an unusual pathological morphology.

How I Diagnose Primary Mediastinal (Thymic) Large B-Cell Lymphoma

OBJECTIVES

Primary mediastinal (thymic) large B-cell lymphoma (PMBL) is an uncommon large B-cell neoplasm recognized by the World Health Organization as a distinct entity on the basis of its unique clinical features, histogenesis, phenotype, and pathogenetic mechanisms. The diagnosis of PMBL can be challenging because of features that may overlap with other (Hodgkin and non-Hodgkin) lymphoma types. This review describes our approach to the diagnosis of PMBL.

METHODS

Two cases are presented to illustrate how we diagnose PMBL and separate PMBL from related histologic and biological mimickers, such as Hodgkin lymphoma and gray zone lymphoma.

RESULTS

A diagnosis of PMBL requires correlation of morphology and immunophenotype with clinical and staging data. Gene expression analysis is not typically performed in clinical labs but has expanded our understanding of the functional pathways underlying this disease and helped identify biomarkers that can be translated to diagnostic practice and possibly to future therapeutic options.

CONCLUSIONS

PMBL and closely related entities can pose diagnostic challenges. It is important to understand the borders between PMBL and other closely related lymphoma types so that patients receive successful primary treatment with curative intent.

Primary mediastinal large B-cell lymphoma in a patient on Fingolimod for relapsing-remitting multiple sclerosis

BACKGROUND

There are multiple case reports in the literature describing an association between fingolimod and cutaneous neoplasms.

OBJECTIVE

Investigate and report a case of a primary mediastinal large B-cell lymphoma in a patient on fingolimod for Relapsing-Remitting Multiple Sclerosis (RRMS).

METHODS

Case Report.

RESULTS

The patient developed a primary mediastinal large B-cell lymphoma after seven years of treatment with fingolimod. The patient is currently in complete remission after cessation of treatment, surgical resection, chemotherapy, and radiation therapy.

CONCLUSION

This case report highlights the first primary mediastinal large B-cell lymphoma associated with fingolimod treatment. It should be considered a rare, but potential adverse effect of fingolimod.

Treatment patterns, healthcare resource utilization, and costs of patients diagnosed with primary mediastinal B-cell lymphoma in the United States

AIMS

With the advent of ICD-10-CM codes for PMBCL on 10/01/2015, assessment of treatment patterns and healthcare burden among US patients is possible. This study sought to describe the real-world treatment patterns and economic outcomes of patients with PMBCL.

METHODS

Data from the Optum Clinformatics DataMart database was used (January 2013-March 2018). Patients with a first PMBCL ICD-10-CM diagnosis (with or without an antecedent ICD-10-CM diagnosis of DLBCL/other lymphoma, which may have been assigned before PMBCL confirmation) after 10/01/2015 (index date) and no ICD-9-CM diagnosis code for unspecified PMBCL/DLBCL were identified as incident patients. Those with PMBCL ICD-10-CM and unspecified ICD-9-CM diagnosis for PMBCL/DLBCL before 10/01/2015 (index date) were identified as prevalent patients. Patients were observed from the index date up to the earliest among death, end of data availability, or end of continuous health plan enrollment. An adapted algorithm was used to identify lines of therapy (LOT).

RESULTS

Among 118 incident and 30 prevalent PMBCL patients, 14% and 20% of patients received ≥2 LOTs, respectively. In incident patients, 48% received ≥1 LOT, 14% ≥2, and 4% ≥3 LOTs. Among prevalent patients, 63% received ≥1 LOT and 20% ≥2 LOTs. The most frequently recorded 1 L therapy was R-CHOP both among incident and prevalent patients. Mean total healthcare costs for incident and prevalent patients were $149,340 and $92,799 per patient per year, respectively, with higher costs ≤12 months ($187,241 and $167,553). Outpatient costs were the main driver (accounting for 60.5% and 64.6% for incident and prevalent patients, respectively).

LIMITATIONS

Potential underuse of ICD-10-CM codes shortly after discontinuation of ICD-9-CM codes in 01/2015; regimens identified for each LOT using the claims-based algorithm may not reflect the regimen administered.

CONCLUSION

The multiple LOTs necessary for a sizeable minority of patients and the high costs of care highlight the significant unmet needs of PMBCL patients.

Lymphomas of the Mediastinum and Their Differential Diagnosis

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

Comparative pathologic analysis of mediastinal B-cell lymphomas: selective expression of p63 but no GATA3 optimally differentiates primary mediastinal large B-cell lymphoma from classic Hodgkin lymphoma

Background

Interpretation of mediastinal biopsy is often challenging even for experienced pathologists especially when a hematolymphoid neoplasm is suspected. Primary mediastinal large B-cell lymphoma (PMLBCL) and classic Hodgkin lymphoma (CHL) represent two major types of mature B-cell lymphomas of the mediastinum. Although PMLBCL and mediastinal CHL share many clinicopathologic characteristics, their treatment strategies and responses are remarkably different. We therefore aimed to find distinctive histologic or protein markers to better differentiate these two lesions.

Methods

Search for primary mediastinal B-cell lymphomas found 52 consecutive cases from 3 university hospitals of Korea during 2005 to 2012. Among them, 32 cases that were available for additional immunohistochemistry (IHC) assessment were enrolled in this study. These cases consisted of the following: CHL (N = 13), PMLBCL (N = 16), and B-cell lymphoma unclassifiable, with features intermediate between diffuse large B-cell lymphoma and CHL (gray zone lymphoma, N = 3). Along with the clinicopathologic findings, the expression of p63, GATA3 and cyclin E was investigated by IHC in the three categorized lesions mentioned above.

Results

Most clinical features overlapped between PMLBCL and CHL except for the increased disease progression and mortality found in PMLBCL. In the pathologic review, the presence of epithelioid granuloma favored a diagnosis of CHL, whereas reticulated or alveolar patterns of fibrosis were characteristic of PMLBCL. For protein markers, p63 was predominantly positive in PMLBCL (15/16) compared with CHL (2/13), which indicates that p63 is a marker of the highest diagnostic accuracy when calculated by the area under the ROC curve. GATA3 was expressed in the majority of CHL cases (10/13) compared with PMLBCL (0/16), while the expression of cyclin E was only rarely present in a minor population of PMLBCL.

Conclusions

P63 expression in tumor cells, even focal expression, and no GATA3 is the most helpful feature in distinguishing PMLBCL from mediastinal CHL.

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.

A study of the dosimetric characteristics between different fixed-field IMRT and VMAT in early-stage primary mediastinal B-cell lymphoma

This analysis was designed to compare dosimetric parameters among different fixed-field intensity-modulated radiation therapy (IMRT) solutions and volumetric-modulated arc therapy (VMAT) to identify which can achieve the lowest risk of organs at risk (OARs) and treatment delivery efficiently. A total of 16 patients (8 male and 8 female) with early-stage primary mediastinal large B-cell lymphoma (PMBCL) were enrolled with planned gross tumor volume (PGTV) 45 Gy and planning target volume (PTV) 40 Gy. Four different plans were generated: 5-, 7, 9-field IMRT, and VMAT. The dose distributions for PGTV and PTV OARs (lungs, left ventricle, heart, thyroid gland, and breasts) were compared. The monitor units (MUs) and treatment delivery time were also evaluated. Mean conformity index (CI) and homogeneity index (HI) for PGTV in 5F-, 7F-, 9F-IMRT, and VMAT were 1.01 and 1.10, 1.01 and 1.10, 1.01 and 1.10, and 1.01 and 1.11 (p = 0.963 and 0.843), whereas these 2 indices for PTV were 1.04 and 1.22, 1.03 and 1.19, 1.03 and 1.17, and 1.08 and 1.14 (p = 0.964 and 0.969), respectively. D_mean (Gy), V4 (%), D50 (Gy), and D80 (Gy) to the left and right breasts increased by 0.7 Gy and 0.1 Gy, 6.8% and 7.7%, 0.9 Gy and 1.7 Gy, and 1.0 Gy and 1.5 Gy in VMAT, respectively. The 9-beam IMRT plan had the highest MUs (25,762.4 MUs) and the longest treatment delivery time (10.7 minutes); whereas, the VMAT had the lowest MUs (13,345.0) and the shortest treatment delivery time (5.9 minutes). Seven- and 9-field IMRT and VMAT provide improved tumor coverage compared with 5F-IMRT, whereas VMAT shows higher treatment delivery efficiency than IMRT technique. Seven- and 9-field IMRT slightly reduce the low dose radiation exposure of breasts compared with VMAT technique. The 7- and 9-field IMRT and VMAT techniques both can be safely and efficiently delivered to patients with PMBCL.

J chain and myocyte enhancer factor 2B are useful in differentiating classical Hodgkin lymphoma from nodular lymphocyte predominant Hodgkin lymphoma and primary mediastinal large B-cell lymphoma

Although most classical Hodgkin lymphomas (CHLs) are easily distinguished from nodular lymphocyte predominant Hodgkin lymphoma (NLPHL) and primary mediastinal large B-cell lymphoma (PMBL), cases with significant CD20 expression cause diagnostic confusion. Although the absence of OCT-2 and BOB.1 are useful in these circumstances, a variable proportion of CHLs are positive for these antigens. We investigated the utility of J chain and myocyte enhancer factor 2B (MEF2B) in the diagnosis of CHL; NLPHL; PMBL; T-cell/histiocyte-rich large B-cell lymphoma (TCRLBL); and B-cell lymphoma, unclassifiable, with features intermediate between diffuse large B-cell lymphoma and CHL, compared with OCT-2 and BOB.1. J chain and MEF2B highlighted lymphocyte predominant (LP) cells in 20/20 (100%) NLPHLs and were negative in 43/43 (100%) CHLs. Fourteen of 15 (93%) PMBLs and 4/4 (100%) TCRLBLs were MEF2B positive, whereas 67% of PMBLs and 50% of TCRLBLs were J chain positive. Three of 3 B-cell lymphomas, unclassifiable, with features intermediate between diffuse large B-cell lymphoma and CHL, were negative for J chain and MEF2B. J chain and MEF2B were 100% sensitive and specific for NLPHL versus CHL. MEF2B was 100% sensitive and 98% specific for PMBL versus CHL. Whereas loss of OCT-2 and/or BOB.1 expression had a sensitivity of only 86% and specificity of 100% for CHL versus NLPHL, PMBL, and TCRLBL, lack of both J chain and MEF2B expression was 100% sensitive and 97% specific. J chain and MEF2B are highly sensitive and specific markers of NLPHL versus CHL; are particularly useful in highlighting LP cells; and, with rare exception, are of greater utility than OCT-2 and BOB.1 in differentiating CHL from NLPHL and other large B-cell lymphomas.

[Primary mediastinal large B-cell lymphoma in women: about five cases]

Primary mediastinal large B-cell lymphoma (PMBL) is a lymphoma occurring in the anterior mediastinum starting from the cells B of the thymique medullary zone. This is a rare entity characterized by epidemiological, clinical and evolutionary peculiarities as well as by pathological and immunohistochemical peculiarities. We report a case series of 5 patients with diagnosed PMBL hospitalized in Pulmonology Department of Ibn Sina Hospital between January 2012 and May 2016. The average age was 34 years, the median of consultation time was 2 months. Reported symptoms were dyspnea, chest pain, dry cough; two patients suffered from superior vena cava syndrome. LDH level was high in 4 patients. Thoracic imaging showed an anterior mediastinal tissue processing in 5 patients. Histological diagnosis was based on ultrasound-guided transparietal puncture biopsy in 5 patients. The contribution of immunohistochemistry was decisive in all cases. Patients were sent to the National Institute of Oncology for therapeutic management. PMBL prognosis is reserved, it most commonly occurs in young women, which increases the need of aggressive therapy to improve survival rate.

Primary Mediastinal Large B-Cell Lymphoma With Translocations Involving BCL6 and MYC (Double-Hit Lymphoma)

OBJECTIVES

Primary mediastinal large B-cell lymphomas (PMLBCLs) are aggressive lymphomas with characteristic clinical, morphologic, and immunophenotypic features. "Double-hit" (DH) lymphomas are B-cell neoplasms characterized by a translocation involving MYC and either BCL2 or BCL6 In the indexed literature, there are no reported cases of PMLBCL associated with DH or triple-hit events.

METHODS

Herein, we present a case of a 15-year-old girl with PMLBCL who had typical clinical, morphologic, and immunophenotypic features.

RESULTS

Fluorescent in situ hybridization studies showed rearrangements involving MYC and BCL6 We also excluded the possibility of a reciprocal t(3;8) (3q27;8q24) BCL6/MYC translocation.

CONCLUSIONS

This case expands the current spectrum of lymphomas subtypes in which DH can be found and supports the rationale for cytogenetic testing for DH abnormalities in all cases of aggressive large B-cell lymphomas regardless of subtype.

Favorable outcome of primary mediastinal large B-cell lymphoma patients treated with sequential RCHOP-RICE regimen without radiotherapy

PURPOSE

Outcomes in primary mediastinal B cell lymphoma (PMBL) improved with the introduction of dose intense treatments, consolidation radiotherapy and rituximab. DA-EPOCH-R, which omits radiotherapy has been adopted with worldwide enthusiasm, despite lack of proven superiority in randomized trials. We aimed to evaluate the course and outcome of PMBL using an alternative intensive rituximab-containing regimen, RCHOP-RICE. We also evaluated the prognostic value of (18)FDG-PET-CT (PET-CT).

METHODS

We reviewed the clinical, laboratory and imaging data of PMBL patients receiving 1st-line treatment in Hadassah Medical Center between 8/2002 and 10/2014.

RESULTS

Of 47 PMBL patients, 24 (51 %) were treated with RCHOP-RICE and 23 (49 %) with other protocols. Overall, the 5-year progression-free survival was 93 % and the overall survival was 98 % (87 and 100 %, respectively, for the RCHOP-RICE regimen). Patient characteristics and treatment toxicities were balanced among protocols. A mean of 11.1 ± 1.3 hospitalization days/patient were needed to administer RCHOP-RICE regimen compared to 37 ± 2 days/patient for DA-EPOCH-R (n = 2). Radiotherapy was given to 3 patients (12 %) treated with RCHOP-RICE compared to 18 patients (78 %) treated with other protocols (p < 0.01). For patients followed with interim and end of treatment (EOT) PET-CT, we observed a significant reduction in the uptake between the two (p < 0.0001). Using a Deauville score cutoff of 3, the negative and positive predictive values (NPV and PPV) of EOT PET-CT were 94 and 33 %, respectively.

CONCLUSIONS

The RCHOP-RICE protocol results in excellent survival outcomes, generally permits omission of RT and is simpler to administer than DA-EPOCH-R. Interim PET-CT in PMBL may be unjustified; however, EOT Deauville scores ≤3 predicts a favorable outcome.

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.

A single-institution retrospective analysis of outcomes for stage I-II primary mediastinal large B-cell lymphoma treated with immunochemotherapy with or without radiotherapy

As the optimal treatment for primary mediastinal large B-cell lymphoma (PMBCL) remains undefined, we evaluated outcomes of patients treated with standard and dose-intense rituximab-chemotherapy (R-CT) with and without radiotherapy (RT). We retrospectively identified 28 patients with stage I-II PMBCL in our lymphoma database, re-reviewed pathology slides and scored interim or post-chemotherapy PET/CTs using the Deauville scale. Fourteen patients received RT (36-45 Gy) preceded by either six cycles of rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) or 12 weeks of rituximab, etoposide, doxorubicin, cyclophosphamide, vincristine, prednisone and bleomycin (R-VACOP-B) with median follow-up of 94 months. Fourteen patients received 4-8 cycles of dose-adjusted etoposide, vincristine, doxorubicin, cyclophosphamide and rituximab (DA-EPOCH-R) with median follow-up of 38 months; one of these received RT (36 Gy) due to post-chemotherapy PET/CT Deauville score 4. Following R-CT and RT or DA-EPOCH-R, 5-year and 3-year FFP and OS were both 100%. Both R-CHOP/R-VACOP-B with RT and DA-EPOCH-R demonstrate excellent outcomes.

Primary mediastinal large B-cell lymphoma arising from thyroid in a renal recipient with Hashimoto's thyroiditis

Primary mediastinal large B-cell lymphoma is a subtype of diffuse large B-cell lymphoma, arising in the mediastinum from putative thymic B-cell origin with distinctive clinical and genetic features. Generally, primary mediastinal large B-cell lymphoma is believed as only deriving in the mediastinum. The current study presents a rare case of primary mediastinal large B-cell lymphoma which arising from thyroid in a renal recipient with Hashimoto's thyroiditis. Moreover, we devoted a discussion to the relationship among primary mediastinal large B-cell lymphoma, immunomodulatory therapy and autoimmune diseases. The immunologic derangement induced by long-term immunomodulatory therapy and Hashimoto's thyroiditis may be the possible cause for the ectopic lymphoma.

Primary mediastinal large B-cell lymphoma

The management of primary mediastinal large B-cell lymphoma (PMBCL) requires a balance between optimizing chances of cure and reducing risk of long-term toxicities. The combination of rituximab to cyclophosphamide, doxorubicin, vincristine and prednisone (RCHOP) followed by mediastinal radiation results in a plateau in progression-free survival after first few years of follow-up. In rituximab era, a negative positron emission tomography (PET) scan performed after the completion of immunochemotherapy has a high predictive value for durable remission. Consequently, end-of-therapy PET may be utilizable to avoid radiation without compromising survival. Additionally, intensified chemotherapy alone has shown excellent survival. PMBCL is frequently associated with amplification of programmed death ligand (PDL) 1/2 and constitutive activation of JAK-STAT and NFKB pathways; these may serve as promising therapeutic targets. Clinical trials that integrate novel therapies into upfront immunochemotherapy and utilize end-of-therapy PET scan to guide mediastinal radiation have potential to further enhance survival and prevent long-term toxicities.

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.

Activating mutations affecting the NF-kappa B pathway and EZH2-mediated epigenetic regulation are rare events in primary mediastinal large B-cell lymphoma

BACKGROUND

Primary mediastinal large B-cell lymphoma (PMBL) is a distinct subtype of diffuse large B-cell lymphoma (DLBCL) frequently observed in young patients. High-dose immunochemotherapy constitutes the current therapeutic gold-standard, despite significant toxicity and serious late effects. Several hotspots harboring oncogenic gain-of-function mutations were recently shown to pose vital hallmarks in activated B-cell like (ABC-) (CD79B, CARD11 and MYD88) and germinal center like (GCB-) DLBCL (EZH2), respectively. Several promising targeted-therapy approaches, derived from these findings, are currently under development.

MATERIALS AND METHODS

We thoroughly characterized a cohort of 25 untreated patients with de novo PMBL by immunohistochemical and cytogenetic means and assessed the prevalence of activating mutations affecting EZH2, CD79B and CARD11 utilizing a polymerase chain reaction (PCR)-based capillary sequencing approach. Moreover, the MYD88 p. L265P status was assessed by employing a pyrosequencing approach.

RESULTS

PMBLs included in this study did not harbor any of the reported hotspot mutations activating the nuclear factor (NF)-kappa B signaling cascade or the EZH2-mediated epigenetic deregulation of gene expression. Immunohistochemical characterization revealed an ABC phenotype in 44% (n=11) of cases.

CONCLUSION

We report that genetic alterations of these genes are rare events in PMBL unlike other subtypes of DLBCL. Our findings suggest that a substantial subset of PMBL patients may benefit from treatment approaches targeting BCR-mediated activation of NF-kappa B.