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

A case of suspected primary mediastinal large B-cell lymphoma: An uncommon cause of sudden death

Primary mediastinal large B-cell lymphoma (PMLBCL) is an aggressive tumor originating from thymic B-cells. Clinically, it presents with general signs such as cough, chest pain and dyspnea. Although these symptoms are not specific, they are severe enough to reveal the disease. We report an autopsy case of a 25-year-old man, with a recent past history of cough and dyspnea, for which he consulted twice the emergency department and no diagnosis was made. He presented to the Emergency Unit, with a sudden onset of a dyspnea followed by a loss of consciousness. He was shortly declared dead after, a medico-legal autopsy was requested. On external examination, no traumatic lesions on the body were found, an important cyanosis of the face and ears, was, however, found. On autopsy, a mediastinal mass was found, measuring 19 cm × 25 cm and weighing 600 g, extending to the infra-hyoid region and to the thoracic cage and infiltrating the pericardium. Trachea had a necrotic mucosa with a partially obstructive lymph node mass. The diagnosis of a primary mediastinal large B-cell lymphoma was suspected based on pathological and immunohistochemical findings. The cause of death was finally attributed to respiratory failure due to this tumor.

Primary mediastinal/thymic diffuse large B-cell lymphoma: a population-based study on incidence and survival

Primary mediastinal large B-cell lymphoma is a rare subtype of lymphoma. The contemporary incidence of primary mediastinal large B-cell lymphoma remains unknown, and a large population-based study has not been reported. It is essential to provide guidance for further strategies in reducing the disease burden via population-based preventive initiatives. This study aims to explore the epidemiology and effect of therapeutic advances on the survival of patients with primary mediastinal large B-cell lymphoma. This population-based study was conducted using the Surveillance, Epidemiology, and End Results Program (SEER), covering the period from 1975 to 2018. A total of 774 patients in the SEER 9 and 1654 patients in the SEER 18 were analyzed. The age-adjusted incidence rate of primary mediastinal large B-cell lymphoma increased from 0.05/1,000,000 in 1975 to 2.38/1,000,000 in 2018. A significant positive linear increase in the incidence trend was found in primary mediastinal large B-cell lymphoma, with an annual percent change of 8.47% (95% confidence interval 7.7-9.2%, P < 0.001, z test). The survival in primary mediastinal large B-cell lymphoma was significantly superior to nodal diffuse large B-cell lymphoma. The incidence of PMBCL increases over the year. The survival of patients with primary mediastinal large B-cell lymphoma has improved over time.

A comparison and review of the flow cytometric findings in classic Hodgkin lymphoma, nodular lymphocyte predominant Hodgkin lymphoma, T cell/histiocyte rich large B cell lymphoma, and primary mediastinal large B cell lymphoma

The "Hodgkin-like" lymphomas including classic Hodgkin lymphoma, nodular lymphocyte predominant Hodgkin lymphoma, T cell/histiocyte rich large B cell lymphoma, and primary mediastinal large B cell lymphoma have been shown to be pathobiologically related. With the exception of primary mediastinal large B cell lymphoma, these lymphomas have similar morphologic growth patterns with occasional neoplastic cells within a prominent reactive cell background. Historically, distinguishing these entities was difficult by flow cytometry; however, over the past 15 years, our laboratory has developed antibody-fluorochrome combinations capable of accurately distinguishing these entities by their immunoprofile. Additionally, an algorithmic approach based on characterization of the background reactive B-cell and T-cell populations can aid in narrowing the differential diagnosis. This review summarizes both the morphologic and immunophenotypic features and the current flow cytometric insights of the neoplastic and reactive populations found in this unique subset of lymphomas.

Disseminated thymic B-cell lymphoma in a Holstein heifer

A 19-mo-old Holstein heifer was inactive and dyspneic. Physical examination revealed wheezing, exophthalmos, a cervical mass, and lymphadenopathy. Cytology of the cervical mass and lymph nodes showed predominantly large atypical lymphocytes. Lactate dehydrogenase and thymidine kinase activities were elevated. Although nested PCR for bovine leukemia virus (BLV) using blood was positive, quantitative PCR showed a low number of provirus copies. Autopsy revealed enlargement of most lymph nodes examined, as well as white masses of various sizes in muscles of the left hindlimb and thoracic and abdominal organs. Histopathology revealed severe infiltration with neoplastic lymphocytes in these organs. The cervical mass was immune-positive for B-cell markers. The final diagnosis was thymic B-cell lymphoma with BLV infection.

Advances in Diagnosis and Management of Diffuse Large B-cell Lymphoma

The management of diffuse large B-cell lymphoma (DLBCL) has been gradually evolving since the discovery of its 2 major forms, the germinal center B-like (GCB) and activated B-cell (ABC) types. Although the reference standard for the identification of these cell types is considered gene expression profiling (GEP), currently the only method commercially available is immunohistochemistry (IHC). The application of various IHC-based algorithms and their correlation with GEP and clinical outcome are discussed. Because of the adverse prognostic implications of the non-GCB type and its potential effects on treatment selection, the recently revised World Health Organization classification has included these biologic cell types. The management of double hit lymphomas, which almost exclusively fall under the GCB category, is discussed, together with the double expresser phenotype, which is usually grouped under the non-GCB type. The role of lenalidomide and ibrutinib in the management of the non-GCB type is examined. We also discuss the front-line management of primary mediastinal large cell lymphoma using the EPOCH (etoposide, prednisolone, Oncovin [vincristine], cyclophosphamide, hydroxydaunorubicin [doxorubicin]) regimen and examine new salvage data on immune checkpoint inhibitors for this clinical subtype. The prognosis, clinical features, and management of de novo CD5+ DLBCL are discussed, and newer and promising developments in the management of primary central nervous system lymphomas are presented in detail. The most popular salvage regimens and the application of high-dose chemotherapy with stem cell transplantation are assessed in detail. Finally, data on new treatment tactics such as CART (chimeric antigen receptor T-cell) cells and promising new drugs, including blinatumomab and venetoclax, are presented.

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.

Immune checkpoint blockade for hematologic malignancies: a review

Immune checkpoint blockade has revolutionized the treatment of cancer, with impressive responses seen in a broad variety of tumor types. Blockade of immune checkpoints and immune signaling antibodies has shown promise in multiple types of hematologic malignancies (HMs), with dramatic single agent responses for pembrolizumab and nivolumab in Hodgkin lymphoma (HL). In this review, we outline the current state of immune checkpoint blockade drug development in HMs, and discuss mechanisms of activity and resistance, and highlight potential targets in the immune tumor microenvironment (TME). Blockade of T-cell checkpoint molecules PD-1/PD-L1 and CTLA-4 are the most clinically mature of the immune checkpoint strategies. Novel and upcoming strategies for immune checkpoint blockade drug development in HMs using innovative combinations to modulate immunologic targets shows significant promise as a way to expand the number of patients with blood cancers who could benefit from immunotherapy.

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.

Update in large cell lymphoma: understanding the pathology report

The diffuse aggressive large B-cell lymphomas are a heterogeneous group of B-cell malignancies. Although many are readily recognized due to characteristic clinical and pathologic features, several problematic areas still exist in diagnosis of these lymphomas due to a variety of reasons that include imprecise or difficult-to-apply diagnostic criteria, gaps in our understanding of lymphoma biology, and limitations in technologies available in the clinical laboratory compared to the research laboratory. This may result in some degree of confusion in the pathology report, particularly if the issues are not clearly explained, leading to frustration or misinterpretation on the part of the reader. In this review, I will discuss the pathologic features of a subset of the WHO 2008 classification diffuse aggressive large B-cell lymphomas, focusing on areas in which difficulties exist in diagnosis and/or biomarker marker assessment. A deeper understanding of the issues and areas of uncertainty due to limitations in our knowledge about the biology of these diseases should lead to better communication between pathologists and clinicians.

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.

Genomic rearrangements involving programmed death ligands are recurrent in primary mediastinal large B-cell lymphoma

The pathogenesis of primary mediastinal large B-cell lymphoma (PMBCL) is incompletely understood. Recently, specific genotypic and phenotypic features have been linked to tumor cell immune escape mechanisms in PMBCL. We studied 571 B-cell lymphomas with a focus on PMBCL. Using fluorescence in situ hybridization here, we report that the programmed death ligand (PDL) locus (9p24.1) is frequently and specifically rearranged in PMBCL (20%) as compared with diffuse large B-cell lymphoma, follicular lymphoma, and Hodgkin lymphoma. Rearrangement was significantly correlated with overexpression of PDL transcripts. Utilizing high-throughput sequencing techniques, we characterized novel translocations and chimeric fusion transcripts involving PDLs at base-pair resolution. Our data suggest that recurrent genomic rearrangement events underlie an immune privilege phenotype in a subset of B-cell lymphomas.

Unclassifiable B-cell lymphoma occurring after necrotizing pneumonia

We report a case of CD20+ grey zone lymphoma (GZL) with Reed Sternberg cells as an unexpected pathological diagnosis of a destroyed right lower lobe after necrotizing pneumonia. These GZLs show overlapping features of classical Hodgkin's lymphoma and diffuse large B-cell lymphoma. GZLs are a rare specific entity of lymphomas, and the aetiology is unknown. The diagnosis is confirmed by pathological, immunohistochemical and molecular analyses. The optimal treatment is unknown. The prognosis of these patients is poor.

PIM2 inhibition as a rational therapeutic approach in B-cell lymphoma

PIM serine/threonine kinases are overexpressed, translocated, or amplified in multiple B-cell lymphoma types. We have explored the frequency and relevance of PIM expression in different B-cell lymphoma types and investigated whether PIM inhibition could be a rational therapeutic approach. Increased expression of PIM2 was detected in subsets of mantle cell lymphoma, diffuse large B-cell lymphoma (DLBLC), follicular lymphoma, marginal zone lymphoma-mucosa–associated lymphoid tissue type, chronic lymphocytic leukemia, and nodal marginal zone lymphoma cases. Increased PIM2 protein expression was associated with an aggressive clinical course in activated B-like-DLBCL patients. Pharmacologic and genetic inhibition of PIM2 revealed p4E-BP1(Thr37/46) and p4E-BP1(Ser65) as molecular biomarkers characteristic of PIM2 activity and indicated the involvement of PIM2 kinase in regulating mammalian target of rapamycin complex 1. The simultaneous genetic inhibition of all 3 PIM kinases induced changes in apoptosis and cell cycle. In conclusion, we show that PIM2 kinase inhibition is a rational approach in DLBCL treatment, identify appropriate biomarkers for pharmacodynamic studies, and provide a new marker for patient stratification.