The Spectrum of Epstein-Barr Virus (EBV)-Positive Diffuse Large B-Cell Lymphoma and EBV-Positive Classic Hodgkin Lymphoma: A Proposed Classification of EBV-Positive Large B-Cell Lymphoma

Introduction: Epstein Barr virus (EBV)-positive diffuse large B-cell lymphoma (DLBCL) is a large B-cell lymphoma with EBV infection which mostly occur in elderly patients. A histological continuum from monomorphic (mDLBCL) to polymorphic (pDLBCL) has been described. Since some cases of pDLBCL mimic classic Hodgkin lymphoma (CHL), distinguishing EBV⁺DLBCL from EBV⁺CHL could be a diagnostic problem. A previous study defined cases with CD20+ neoplastic cells ≥50% as EBV⁺DLBCL and <50% as EBV⁺CHL (Asano N, et al. Blood. 2009). However, this criterion is arbitrary, and the boundary between the two entities remains indistinct. To address this issue, we aimed to characterize and reclassify the spectrum of EBV⁺DLBCL and EBV⁺CHL.

Methods: We identified 57 patients, aged 50 years or older, who were diagnosed with EBV⁺DLBCL or EBV⁺CHL at Tokai University Hospital from 2006 to 2021. Cases in which EBV was confirmed in more than 50% of the tumor cells by EBER in situ hybridization were retrieved. Patients with immune deficiency/dysregulation secondary to inborn errors of immunity, HIV infection, transplantation, autoimmune disease, immunosuppressive/immunomodulatory medications, or a prior history of lymphoma were excluded. Gene expression profiling (GEP), fluorescence in situ hybridization (FISH) for 9p24.1/PD-L1, and immunohistochemistry (IHC) with CD3, CD5, CD10, CD15, CD20, CD30, Ki67, PAX5, PD-L1, IDO1, LMP1, and EBNA2 were performed using formalin fixed paraffin embedded tissue.

Results: The series was comprised of 35 cases of EBV⁺DLBCL, 12 pDLBCL and 23 mDLBCL, and 22 cases of EBV⁺CHL. EBV latency type (I/II/III) was 1/20/14 in EBV⁺DLBCL (0/11/1 in pDLBCL and 1/9/13 in mDLBCL) and 0/22/0 in EBV⁺CHL. 9p24.1 amplification/copy gain was found in 100% (18/18) of EBV⁺CHL, 53% (8/15) of types I/II-DLBCL, and 27% (3/11) of type III-DLBCL cases. Median PD-L1 H-score was 250 (interquartile range 200-260) in EBV⁺CHL, 180 (105-210) in types I/II-DLBCL, and 70 (40-120) in type III-DLBCL. GEP revealed that the level of IDO1, an enzyme which plays an immunosuppressive role, is significantly high in types I/II-DLBCL compared to type III-DLBCL and EBV⁺CHL. IHC showed that IDO1 was expressed in dendritic cells/histiocytes, but not in neoplastic cells. Multivariate analysis of the total cohort including both EBV⁺DLBCL and EBV⁺CHL revealed that each of EBV latency type III and ECOG performance status 2-4 was associated with a shorter overall survival (hazard ratio, 5.12 and 3.32, respectively; 95% confidence interval, 1.54-17.0 and 1.22-9.04, respectively), but not the diagnosis of DLBCL defined by CD20 positivity.

Conclusions: The spectrum of EBV⁺DLBCL and EBV⁺CHL could be reclassified into four groups of EBV⁺ large B-cell lymphoma according to the mechanism of tumor-host interactions: Cases with 9p24.1 amplification/copy gain and PD-L1 expression (PD-L1-group), cases with IDO1-rich tumor microenvironment (IDO1-group), cases with EBV latency type III (immune senescence; IS-group), and not otherwise specified (NOS-group). The former two groups with immune escape mechanism exhibit relatively good prognosis, and PD-1/PD-L1 and IDO1 inhibitors could be effective therapeutic options. In contrast, IS-group exhibits extremely unfavorable prognosis with less tolerogenic mechanism. This may be attributable to underlying immune senescence and different clinical approach should be warranted. Thus, a proposed classification of EBV⁺ large B-cell lymphoma is beneficial for both pathological diagnosis and clinical management.

Kawada:CHUGAI PHARMACEUTICAL CO., LTD.: Research Funding; Kyowa Kirin Co., Ltd.: Research Funding. Nakamura:Janssen Research & Development, LLC: Research Funding.