Variable Expression of B-cell Transcription Factors in Reactive Immunoblastic Proliferations: A Potential Mimic of Classical Hodgkin Lymphoma

Differentiating fulminant EBV infection complicated by HLH from Lymphoma: report of a case and a brief literature review

Epstein-Barr virus (EBV) infection may present with fulminant constitutional symptoms, cytopenia(s), and systemic lymphadenopathy, raising clinical suspicion for lymphoma and prompting lymph node and bone marrow biopsies. At the microscopic level, the histopathologic findings in cases of acute EBV lymphadenitis may mimic certain lymphoid neoplasms, creating a range of differential diagnoses and diagnostic pitfalls.We present a case of fulminant EBV infection in an adolescent whose clinical and radiographic findings led to lymph node and bone marrow biopsies to rule out lymphoma. One week after being diagnosed with acute EBV infection (infectious mononucleosis), a 17-year-old Caucasian male presented with worsening symptoms including persistent fever, progressive, painful lymphadenopathy, and splenomegaly. A peripheral blood smear showed lymphocytosis with many reactive lymphocytes, anemia, and thrombocytopenia. Laboratory studies showed elevated ferritin, triglycerides, and soluble IL-2/CD25. A cervical lymph node biopsy demonstrated an EBV-positive, reactive B-immunoblast proliferation with large atypical lymphoid cells mimicking Reed-Sternberg cells of Hodgkin lymphoma, in addition to patchy vasculitis, coagulative necrosis, and prominent hemophagocytic activity. Bilateral bone marrow biopsies showed a hypercellular marrow with patchy infiltrates of similar EBV-positive, large atypical lymphoid cells, as well as prominent hemophagocytic activity. The diagnosis of acute EBV associated lymphoproliferation with concurrent hemophagocytic lymphohistiocytosis (HLH) was rendered.Recognition of common and uncommon clinical presentations of acute EBV infection is essential, particularly when histopathologic findings raise suspicion for a possible hematolymphoid neoplasm. Both the lymph node architectural and viral cytopathic changes observed in EBV lymphadenitis exhibit significant morphologic overlap with classic Hodgkin lymphoma (cHL) and several other lymphomas, including anaplastic large cell lymphoma, diffuse large B cell lymphoma, and angioimmunoblastic T cell lymphoma. Recognition of immunohistochemical staining patterns in EBV lymphadenitis is critical to avoid misdiagnosis. Conversely, bona fide lymphoma, particularly cHL, can masquerade as EBV infection. We provide a concise discussion and tables of the histopathologic differential diagnosis of EBV lymphadenitis, including cHL and other lymphomas. Pathologists should include acute EBV infection within the differential diagnosis when confronted with clinical and pathologic findings concerning for lymphoma, particularly in adolescents and young adults.

[Reactive lymphadenopathies]

The human body comprises around 600 lymph nodes as constituents of a decentralized and dispersed immune system. The main task of lymph nodes is cleaning the lymph fluid and defending the organism against outer and inner threats by bacteria, viruses and tumour cells. The histologic picture of lymph nodes reflects the different strategies of the innate and adaptive immune system, which allocates antigen presenting cells, macrophages, B‑ and T‑cell systems and reticulum cells. However, the histological picture, without any additional investigations, usually only allows speculation about the causative agent like toxoplasmosis, other bacteria or viruses. This chapter describes different lymph node reactions in detail in order to obtain a better understanding of specific immune reactions allowing a precise diagnosis and a reliable distinction from malignant processes. The last issue in particular is one of the main tasks of haematopathology. In addition to these known principles, we try to integrate results obtained with the new method of three-dimensional (3D) microscopy of fixed lymphoid tissue. At first glance, this seems to be unusual. Nevertheless, we try to apply this approach, since 3D visualization of morphological details provides distinct cellular details as well as new interpretations of cell-cell interactions and the functions of lymphoid compartments, like germinal centres and T‑zones.

Reactive Intralymphovascular Immunoblastic Proliferations Mimicking Aggressive Lymphomas

Reactive intralymphovascular immunoblastic proliferations (ILVIPs) may mimic aggressive lymphomas and are rarely reported. Herein, we characterize the clinicopathologic features of 8 patients with ILVIPs. No patients had lymphadenopathy, hepatosplenomegaly, or other findings suggestive of lymphoma. The ILVIPs involved the small or large intestine (n=5) and appendix (n=3). Patients were evaluated for abdominal pain, suspected appendicitis, intestinal obstruction, diverticulitis, volvulus, or tumor resection. Histologic sections showed expanded lymphovascular spaces filled by intermediate to large immunoblasts, positive for CD38, CD43, CD45, CD79a, and MUM1/IRF4 in all cases tested. Five of 6 (83%) cases were positive for CD30. CD20 was weakly positive in a subset of cells in 2 (25%) cases, and PAX5 was weakly positive in 4 (50%) cases. The immunoblasts expressed polytypic light chains in all cases tested. In 1 case, a subset of immunoblasts expressed T-cell markers indicating the presence of a T-cell component. The immunoblasts were negative for ALK, BCL-2, BCL-6, CD10, CD56, CD138, and Epstein-Barr virus-encoded small RNA in all cases assessed. The proliferation index shown by Ki-67 was high with a median of 80%. In all 6 cases tested, the immunoblasts were shown within lymphatic channels highlighted by D2-40. In conclusion, ILVIPs can be rarely observed in patients with inflammatory or infectious conditions, especially in gastrointestinal tract surgical specimens. The immunoblasts are predominantly of B-lineage with a postgerminal center immunophenotype and are located within lymphatic channels. It is essential to distinguish reactive ILVIPs from aggressive lymphomas to avoid unnecessary therapy.

The Grey Zones of Classic Hodgkin Lymphoma

Simple Summary

Classic Hodgkin lymphoma (CHL) is a well-defined lymphoid neoplasm with a minority of characteristic neoplastic cells of B cell origin, namely Hodgkin and Reed–Sternberg cells immersed in a rich reactive inflammatory infiltrate in the background. Although CHL has always been set apart from non-Hodgkin lymphomas, cases with morphological and phenotypic features intermediate between CHL and other lymphomas have been described. Whereas some of these lymphomas only represent morphological mimics, others exhibit mutational and gene expression profiles which overlap with CHL, indicating that these cases, frequently termed grey zone lymphomas, reside on the biological boundary between CHL and large B-cell lymphomas. In the present review, we aim to describe the current knowledge of these rare lymphomas, address diagnostic issues and summarize today’s concepts on the classification of grey zone lymphomas and related tumors.

Abstract

Classic Hodgkin lymphoma (CHL) is a well-defined neoplasm characterized by the presence of a minority of pathognomonic Hodgkin and Reed–Sternberg (HRS) cells in a reactive inflammatory background. Although genotypically of B cell origin, HRS cells exhibit a downregulated B cell program and therefore are set apart from other B cell lymphomas in the current WHO classification. However, cases with morphological and phenotypic features overlapping with CHL have been recognized, and the category of B cell lymphoma—unclassifiable—with features intermediate between diffuse large B cell lymphoma (DLBCL) and CHL, also termed grey zone lymphoma, was first introduced into the WHO classification in 2008 as provisional entity. These cases, as well as others raising a differential diagnosis of CHL can present diagnostic problems, as well as therapeutic challenges. Whereas some of these lymphomas only represent biologically unrelated morphological mimics, others, especially mediastinal grey zone lymphoma, exhibit genetic and gene expression profiles which overlap with CHL, indicating a true biological relationship. In this review, we address areas of diagnostic difficulties between CHL and other lymphoma subtypes, discuss the biological basis of true grey zone lymphoma based on recent molecular studies and delineate current concepts for the classification of these rare tumors.

Role of FNA with core biopsy or cell block in patients with nodular lymphocyte-predominant Hodgkin lymphoma

BACKGROUND

Nodular lymphocyte-predominant Hodgkin lymphoma (NLPHL) represents a diagnostic challenge on surgical excisional or incisional biopsy. Classification is further challenging on fine needle aspiration (FNA) material accompanied by needle core and/or cell block biopsy (FNA+core/CB).

METHODS

The authors studied all FNA+core/CB and surgical excisional or incisional biopsies to evaluate for lymphoma in patients who had a prior history of NLPHL or subsequent diagnosis of NLPHL over a 5-year period from 2012 through 2016.

RESULTS

Patients who ultimately were diagnosed with NLPHL represented <0.5% of those who underwent FNA+core/CB for an initial suspicion of lymphoma. FNA+core/CB resulted in a definitive diagnosis in 7 of 13 cases, and surgical excisional or incisional biopsy specimens resulted in a definitive diagnosis in 13 of 13 cases (chi-square statistic, 9.6; P = .002). At initial diagnosis, FNA+core/CB was negative in 2 cases and atypical or suspicious in 3 cases; all 5 of those patients required surgical excisional or incisional biopsy for a definitive lymphoma diagnosis. By contrast, patients who underwent FNA+core/CB for recurrent lymphoma required surgical excisional or incisional biopsy in only 1 of 8 cases (chi-square statistic, 9.5; P = .002). Flow cytometry was positive for a light-chain-restricted B-cell population in only 1 of 11 biopsies that were involved by lymphoma.

CONCLUSIONS

Surgical excisional or incisional biopsy remains the gold standard for NLPHL diagnosis and for distinguishing progression to a T-cell/histiocyte-rich large B-cell lymphoma pattern. At a tertiary cancer center with routine collaborative diagnosis of lymphoma on FNA+core/CB by cytopathologists and hematopathologists, FNA+core/CB performs well to assess for recurrent or transformed NLPHL, rarely requiring subsequent surgical excisional or incisional biopsy. FNA+core/CB has limited sensitivity in the initial diagnosis setting.

Pearls and pitfalls in the diagnostic workup of small lymph node biopsies

All pathology subspecialties are more frequently receiving small needle core biopsies for the diagnosis of new lesions. While this results in potential diagnostic pitfalls, the tools available for hematopathology, including extensive panels of immunostains, PRC-based clonality assessment, and flow cytometry often allow accurate diagnoses even with very small specimens. This review presents a brief approach to such biopsies, using morphologic cues as well as ancillary studies, which provides an experience-based framework for approaching these cases and coming to a clear diagnosis while avoiding diagnostic errors. The approach is divided into three parts based on H & E cell morphology.

T cell-rich lymphoid infiltrates with large B cells: a review of key entities and diagnostic approach

Accurate diagnostic interpretation of a lymphoid population composed predominantly of small T cells, together with smaller numbers of large B cells, with or without a nodular architecture, is a common problem faced by the histopathologist. The differential diagnosis of this histological pattern is wide, ranging from reactive conditions such as drug reactions and viral infections, through borderline entities such as immunodeficiency-related lymphoproliferative disorders to lymphomas. The latter includes entities where the large B cells are primarily neoplastic (classical and nodular lymphocyte-predominant Hodgkin lymphomas and T cell/histiocyte-rich large B cell lymphoma) as well as T cell lymphomas such as angioimmunoblastic T cell lymphoma where the large B cells represent an epiphenomenon and may or may not be neoplastic. Several rare variants of these conditions, and the fact that treatment can significantly modify appearances, add to the diagnostic difficulty of these pathological entities. Unlike monomorphic lymphoid infiltrates, the histological pattern of T cell-rich proliferation with large B cells requires close evaluation of the inter-relationship between B cells and T cells, follicular dendritic cells and sometimes other inflammatory cells. Epstein-Barr virus plays a key role in several of these scenarios, and interpreting not only its presence but also its distribution within cellular subgroups is essential to accurate diagnosis and the avoidance of some important diagnostic pitfalls. An understanding of normal immunoarchitecture and lymphoid maturational pathways is also fundamental to resolving these cases, as is a knowledge of their common patterns of spread, which facilitates correlation with clinical and radiological findings.