Shigeo Nakamura

Diffuse large B-cell lymphoma (DLBCL) is an aggressive malignancy and is the most common type of malignant lymphoid neoplasm. While some DLBCLs exhibit strong cell-autonomous survival and proliferation activity, others depend on interactions with non-malignant cells for their survival and proliferation. Recent next-generation sequencing studies have linked these interactions with the molecular classification of DLBCL. For example, germinal center B-cell-like DLBCL tends to show strong associations with follicular T cells and epigenetic regulation of immune recognition molecules, whereas activated B-cell-like DLBCL shows frequent genetic aberrations affecting the class I major histocompatibility complex. Single-cell technologies have also provided detailed information about cell–cell interactions and the cell composition of the microenvironment of DLBCL. Aging-related immunological deterioration, i.e., immunosenescence, also plays an important role in DLBCL pathogenesis, especially in Epstein-Barr virus-positive DLBCL. Moreover, DLBCL in “immune-privileged sites”—where multiple immune-modulating mechanisms exist—shows unique biological features, including frequent down-regulation of immune recognition molecules and an immune-tolerogenic tumor microenvironment. These advances in understanding the immunology of DLBCL may contribute to the development of novel therapies targeting immune systems.

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

Hodgkin lymphomas (HLs) are lymphoid neoplasms derived from B cells and consist histologically of large neoplastic cells known as Hodgkin and Reed–Sternberg cells and abundant reactive bystander cells. HLs include two main types, classic HL (CHL) and nodular lymphocyte predominant HL (NLPHL). Recent molecular analyses have revealed that an immune evasion mechanism, particularly the PD-1/PD-L1 pathway, plays a key role in the development of CHL. Other highlighted key pathways in CHL are NF-κB and JAK/STAT. These advances have dramatically changed the treatment for CHL, particularly relapsed/refractory CHL. For example, PD-1 inhibitors are now widely used in relapsed/refractory CHL. Compared with CHL, NLPHL is more characterized by preserved B cell features. Overlapping morphological and molecular features between NLPHL and T-cell/histiocyte-rich large B-cell lymphoma (THRLBCL) have been reported, and biological continuity between these two entities has been highlighted. Some THRLBCLs are considered to represent progression from NLPHLs. With considerable new understanding becoming available from molecular studies in HLs, therapies and classification of HLs are continually evolving. This paper offers a summary of and update on the pathological and molecular features of HLs for a better understanding of the diseases.

Background: There is currently no standard prognostic model optimized for the patients with diffuse large B-cell lymphoma (DLBCL) treated with upfront intensive immunochemotherapy including autologous stem cell transplantation (ASCT). The Kyoto Prognostic Index (KPI) has been proposed as a novel prognostic model for DLBCL, which can accurately identify especially high-risk patients. In this study, we investigated the prognostic value of the KPI in JCOG0908 trial in which higher-risk DLBCL patients defined by the conventional International Prognostic Index (IPI) were treated with upfront high dose therapy followed by ASCT. Methods: Fifty-eight patients with DLBCL, not otherwise specified, enrolled in JCOG0908 and confirmed by the central pathological review were analyzed. The Kaplan–Meier method was used to estimate the probabilities of overall survival (OS) and progression-free survival (PFS). We compared the discrimination ability of the KPI with that of the IPI. Results: According to KPI, 3-year OS and PFS rates were 86.7% and 76.7% in low-intermediate, 73.3% and 60.0% in high-intermediate, and 61.5% and 46.2% in high-risk group. According to IPI, 3-year OS and PFS rates were 75.0% and 50.0% in low-intermediate, 82.9% and 74.3% in high-intermediate, and 63.6% and 54.5% in high-risk group. The concordance-indices of KPI and IPI were 0.642 and 0.580 for OS and 0.606 and 0.606 for PFS. Conclusions: The KPI may be a suitable predictor of outcome than the IPI for patients with higher-risk DLBCL treated with upfront intensive immunochemotherapy including ASCT.

Epstein-Barr virus positive B-cell lymphoproliferative disorder (EBV⁺ B-LPD) encompasses a broad clinicopathological spectrum and distinct clinical behavior that relatively favors the gastrointestinal (GI) tract. In this review, we provide an update on the clinicopathological features and biological behavior of EBV-positive mucocutaneous ulcer (EBVMCU) and primary EBV⁺ diffuse large B-cell lymphoma (DLBCL) of the GI tract. EBVMCU is a newly recognized entity but well known as an indolent and self-limited EBV⁺ B-LPD occurring in various immunodeficiencies. In contrast, EBV⁺ DLBCL constitutes the largest group of EBV⁺ B-LPDs and is regarded as an aggressive neoplasm. These two distinct diseases have historically been distinguished in the reappraisal of age-related EBV-associated B-LPDs but are challenging in routine practice regarding their differential diagnostic and therapeutic approaches. An increasing number of reports indicate that they are epidemiologically prevalent beyond western and eastern countries, but their comprehensive analysis is still limited. We also describe the PD-L1 positivity of tumorous large cells and non-malignant immune cells, which is relevant for the prognostic delineation among patients with primary DLBCL of the GI tract with and without EBV on tumor cells.

T-cell lymphomas arise from a single neoplastic clone and exhibit identical patterns of deletions in T-cell receptor (TCR) genes. Whole genome sequencing (WGS) data represent a treasure trove of information for the development of novel clinical applications. However, the use of WGS to identify clonal T-cell proliferations has not been systematically studied. In this study, based on WGS data, we identified monoclonal rearrangements (MRs) of T-cell receptors (TCR) genes using a novel segmentation algorithm and copy number computation. We evaluated the feasibility of this technique as a marker of T-cell clonality using T-cell lymphomas (TCL, n = 44) and extranodal NK/T-cell lymphomas (ENKTLs, n = 20), and identified 98% of TCLs with one or more TCR gene MRs, against 91% detected using PCR. TCR MRs were absent in all ENKTLs and NK cell lines. Sensitivity-wise, this platform is sufficiently competent, with MRs detected in the majority of samples with tumor content under 25% and it can also distinguish monoallelic from biallelic MRs. Understanding the copy number landscape of TCR using WGS data may engender new diagnostic applications in hematolymphoid pathology, which can be readily adapted to the analysis of B-cell receptor loci for B-cell clonality determination.

Aims: To investigate the clinicopathological features of Epstein–Barr virus (EBV)‐positive grey zone lymphoma (GZL) with features intermediate between diffuse large B‐cell lymphoma (DLBCL) and classical Hodgkin lymphoma (CHL).Methods and results: We investigated the clinicopathological features of 14 cases of EBV‐positive GZL in Japan. The control group included 173 cases of EBV‐positive CHL and 64 cases of EBV‐positive DLBCL of the elderly (polymorphous type). The patients were 10 men and four women with a median age of 62 years. Twelve patients (86%) had advanced clinical stage, 11 (79%) had B‐symptoms, eight (57%) had mediastinal disease, 10 (71%) had elevated serum lactate dehydrogenase (LDH) levels, and five (36%) had thrombocytopenia. All cases had CHL‐like morphology but strongly expressed at least one B‐cell marker. The neoplastic cells were Hodgkin and Reed–Sternberg‐like cells, but with a large number of mononuclear variants. EBV‐positive GZL patients were more significantly more likely than EBV‐positive CHL patients to have advanced clinical stage (P = 0.023), presence of B‐symptoms (P = 0.011), elevated serum LDH levels (P = 0.047), thrombocytopenia (P = 0.042), and mediastinal involvement (P = 0.023). The progression‐free survival (PFS) of EBV‐positive GZL patients was significantly poorer than that of EBV‐positive CHL patients (P = 0.043) but no difference from EBV‐positive DLBCL patients was observed (P = 0.367).Conclusions: EBV‐positive GZL patients have significantly worse PFS than EBV‐positive CHL patients, and are significantly more likely to have adverse clinical parameters such as advanced clinical stage, presence of B‐symptoms, and thrombocytopenia. Further studies are needed to better characterize this entity, which may require the development of innovative therapeutic strategies.

Epstein-Barr virus (EBV) is detected in 20% to 30% of sporadic Burkitt lymphoma (sBL). However, only a few studies of EBV-positive (EBV⁺) sBL have been reported, and its characteristics still remain controversial. To highlight the features of EBV⁺ sBL, we compared the clinicopathologic characteristics of 33 cases of EBV⁺ and 117 cases of EBV-negative (EBV⁻) sBL in Japan. EBV⁺ sBL showed significantly higher age distribution (median, 42 vs. 13 y; PP+ group showed significantly higher incidence of involvement of tonsil (P=0.027), adrenal gland (P=0.011), and cervical lymph node (P=0.040). In addition, the EBV⁺ group tended to have higher incidence of nodal involvement (P=0.078) and involvement of para-aorta lymph node (P=0.084) and heart (P=0.050). In contrast, the gastrointestinal tract was less frequently affected in EBV⁺ sBL (P=0.024). In addition, the less positivity for MUM1 (P=0.020) of EBV⁺ sBL was highlighted. These results indicate that biological behavior and pathogenesis of EBV⁺ sBL might be different from those of EBV⁻ sBL. Our results demonstrate that EBV⁺ sBL has an aspect of age-related disease and is a distinct clinicopathologic subtype, which should be distinguished from EBV⁻ sBL.

To investigate the clinicopathological significance of CD20 expression and Epstein‐Barr virus (EBV) association in Hodgkin and Reed–Sterberg cells of classical Hodgkin lymphoma (CHL), CD20 expression and EBV positivity (by EBER in situ hybridization) were investigated in 389 CHL patients in Japan. They included 74 CD20‐positive cases (19%) and 315 CD20‐negative cases (81%). CD20‐positive cases showed significantly older age at onset (P = 0.018) and higher association with EBV (P = 0.002). Multivariate analysis identified EBV‐positivity (but not CD20‐positivity), presence of B symptoms, thrombocytopenia, elevated serum lactate dehydrogenase and performance status >1 as poor prognostic factors for overall survival (OS). We constructed a new prognostic model with these five factors classifying patients into three groups: low risk, 0–1 adverse factor; intermediate risk, 2–3 factors; high risk, 4–5 factors. This prognostic model could stratify the prognosis of CHL patients (P < 0.0001). For 144 patients (58%) classified into the low‐risk group, the 5‐year OS was 91%. For 92 patients (37%) in the intermediate group, the 5‐year OS was 66%; for 11 patients (5%) in the high‐risk group, the 5‐year OS was 36%. In conclusion, EBV is identified as an independent poor prognostic factor for CHL patients. Therefore, examination of EBV association in CHL is recommended as routine pathologic practice especially in countries where EBV infection prevails.