B-cell differentiation immunophenotypes in classical Hodgkin lymphomas

Initial Diagnosis of Classic Hodgkin Lymphoma With Skin Biopsy: A Rare Case and Review of Diagnostic Considerations

ABSTRACT

Classic Hodgkin lymphoma (CHL) is a B-cell-derived lymphoma that classically displays a bimodal age distribution. CHL typically involves the mediastinum, lymph nodes, and other visceral organs. CHL is characterized histologically by the presence of a relatively paucicellular neoplastic cell population composed of large atypical cells (including Hodgkin and Reed-Sternberg forms) in a reactive mixed inflammatory background, often with prominent necrosis. CHL rarely occurs in the skin, and the associated mixed inflammatory infiltrate or necrotic appearance can create diagnostic uncertainty. Herein, we report the case of a 31-year-old man presenting with a painful dendritic rash of the anterior chest wall with axillary lymphadenopathy. After multiple nondiagnostic biopsies that revealed largely necrotic material, a chest wall skin biopsy was obtained. The skin biopsy was diagnostic of CHL, based on the presence of large atypical dermal cells, including Hodgkin and Reed-Sternberg forms, which expressed CD15, CD30 and Fascin, in a typical mixed inflammatory and necrotic background. Through the lens of this case, we discuss the characteristics and mechanisms of skin involvement of CHL, and the histopathologic and immunohistochemical pitfalls when considering the rare diagnosis of CHL in the skin.

Hodgkin Lymphoma: Biology and Differential Diagnostic Problem

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.

Atypical Phenotypes in Classical Hodgkin Lymphoma

Classical Hodgkin lymphoma has a characteristic immunophenotype in most cases, with expression of CD30, CD15, and PAX-5, and absence of CD45 and T-lineage markers. However, in a significant subset of cases, atypical staining patterns may be seen for one or more antigens, particularly negative staining for CD15 or staining for one or more B-lineage markers, such as CD20, CD79a, OCT-2, or BOB.1. The greatest pitfall is in the misinterpretation of other cells, such as immunoblasts or histiocytes, as Hodgkin cells.

Reed-Sternberg–Like Cells in Non-Hodgkin Lymphomas

Large atypical cells with morphologic and immunophenotypic features resembling Reed-Sternberg cells can be seen in the background of reactive lymphadenopathies as well as non-Hodgkin lymphomas. The presence of these cells is an important diagnostic pitfall that must be recognized by pathologists who regularly interpret lymph node biopsies. A thorough evaluation of the morphologic and immunophenotypic features of these cells and the cellular milieu is crucial in achieving the correct diagnosis. In this review, examples of lymphomas presenting with Reed-Sternberg–like cells will be provided. Additionally, a detailed description of the common morphologic and immunophenotypic features of these cells, as well as strategies that can be used to distinguish them from the Reed-Sternberg cells of classical Hodgkin lymphoma, will be emphasized.

Pediatric Hodgkin lymphoma in a South Indian regional cancer center: its immunomorphology, tumor-associated macrophages, and association with Epstein-Barr virus

Pediatric Hodgkin lymphoma (HL) comprises approximately a fifth of all patients with HL in India. Seventy-four cases of pediatric classical Hodgkin Lymphoma (cHL) from a regional cancer center in southern India were analyzed on a tissue microarray (TMA) for the stage of B-cell differentiation of the Hodgkin/Reed Sternberg (HRS) cell by immunohistochemistry (IHC) using CD10, bcl6, MUM1/IRF4, and CD 138. Fifty-two of seventy-four (70.3%) cases were of late germinal center/early post-germinal center phenotype (CD10-/bcl6-/MUM1+/CD138-). Epstein-Barr virus (EBV) association using Epstein-Barr virus encoded RNA (EBER) RISH and EBV-LMP1 immunohistochemistry (IHC) revealed an EBV association of 93%. Tumor-associated macrophages (TAM) in the microenvironment were also assessed on the TMA by CD68 IHC, and most cases (59.7%) showed >25% TAMs, with no case showing ≤5%. These findings indicate that pediatric cHL in India is a tumor, predominantly, of late germinal center/early post-germinal center B cells, is almost invariably EBV associated, and with a high number of TAMs in the microenvironment. This latter finding suggests that criteria other than TAM scores need to be developed for risk stratification of pediatric EBV-associated HL especially in developing countries.

The role of the microenvironment in human immunodeficiency virus-associated classical Hodgkin lymphoma

AIMS

To characterize the microenvironment of classical Hodgkin lymphoma (cHL) in people living with human immunodeficiency virus (PLWH). The objective was to identify and then quantify the immune cells present in the microenvironment.

METHODS AND RESULTS

Ten samples of cHL from PLWH were compared with 10 samples of cHL from the general population using tissue microarray technology and immunohistochemistry. Sections were immunostained with antibodies for CD30, CD3, CD4, CD8, CD20, CD68R, CD56, CD57, CD123, FoxP3 and granzyme B. A statistically significant reduction of CD4(+) T cells, CD56(+) cells, CD57(+) cells, CD123(+) cells and B cells and an increase in numbers in FoxP3(+) CD8(+) cells was observed in cHL diagnosed in PLWH. No significant differences were seen in the number of CD8(+) T cells, CD4(+) FoxP3(+) T cells and macrophages.

CONCLUSION

There are considerable differences in the microenvironment of cHL occurring with and without HIV.

Fibroblast growth factor-2 (FGF2) and syndecan-1 (SDC1) are potential biomarkers for putative circulating CD15+/CD30+ cells in poor outcome Hodgkin lymphoma patients

Background

High risk, unfavorable classical Hodgkin lymphoma (cHL) includes those patients with primary refractory or early relapse, and progressive disease. To improve the availability of biomarkers for this group of patients, we investigated both tumor biopsies and peripheral blood leukocytes (PBL) of untreated (chemo-naïve, CN) Nodular Sclerosis Classic Hodgkin Lymphoma (NS-cHL) patients for consistent biomarkers that can predict the outcome prior to frontline treatment.

Methods and materials

Bioinformatics data mining was used to generate 151 candidate biomarkers, which were screened against a library of 10 HL cell lines. Expression of FGF2 and SDC1 by CD30+ cells from HL patient samples representing good and poor outcomes were analyzed by qRT-PCR, immunohistochemical (IHC), and immunofluorescence analyses.

Results

To identify predictive HL-specific biomarkers, potential marker genes selected using bioinformatics approaches were screened against HL cell lines and HL patient samples. Fibroblast Growth Factor-2 (FGF2) and Syndecan-1 (SDC1) were overexpressed in all HL cell lines, and the overexpression was HL-specific when compared to 116 non-Hodgkin lymphoma tissues. In the analysis of stratified NS-cHL patient samples, expression of FGF2 and SDC1 were 245 fold and 91 fold higher, respectively, in the poor outcome (PO) group than in the good outcome (GO) group. The PO group exhibited higher expression of the HL marker CD30, the macrophage marker CD68, and metastatic markers TGFβ1 and MMP9 compared to the GO group. This expression signature was confirmed by qualitative immunohistochemical and immunofluorescent data. A Kaplan-Meier analysis indicated that samples in which the CD30+ cells carried an FGF2+/SDC1+ immunophenotype showed shortened survival. Analysis of chemo-naive HL blood samples suggested that in the PO group a subset of CD30+ HL cells had entered the circulation. These cells significantly overexpressed FGF2 and SDC1 compared to the GO group. The PO group showed significant down-regulation of markers for monocytes, T-cells, and B-cells. These expression signatures were eliminated in heavily pretreated patients.

Conclusion

The results suggest that small subsets of circulating CD30+/CD15+ cells expressing FGF2 and SDC1 represent biomarkers that identify NS-cHL patients who will experience a poor outcome (primary refractory and early relapsing).

Transcriptional deregulation of homeobox gene ZHX2 in Hodgkin lymphoma

Recently, we identified a novel chromosomal rearrangement in Hodgkin lymphoma (HL), t(4;8)(q27;q24), which targets homeobox gene ZHX2 at the recurrent breakpoint 8q24. This aberration deletes the far upstream region of ZHX2 and results in silenced transcription pinpointing loss of activatory elements. Here, we have looked for potential binding sites within this deleted region to analyze the transcriptional deregulation of this tumor suppressor gene in B-cell malignancies. SiRNA-mediated knockdown and reporter gene analyses identified two transcription factors, homeodomain protein MSX1 and bZIP protein XBP1, directly regulating ZHX2 expression. Furthermore, MSX1-cofactor histone H1C mediated repression of ZHX2 and showed enhanced expression levels in cell line L-1236. As demonstrated by fluorescence in situ hybridization and genomic array analysis, the gene loci of MSX1 at 4p16 and H1C at 6p22 were rearranged in several HL cell lines, correlating with their altered expression activity. The expression of XBP1 was reduced in 6/7 HL cell lines as compared to primary hematopoietic cells. Taken together, our results demonstrate multiple mechanisms decreasing expression of tumor suppressor gene ZHX2 in HL cell lines: loss of enhancing binding sites, reduced expression of activators MSX1 and XBP1, and overexpression of MSX1-corepressor H1C. Moreover, chromosomal deregulations of genes involved in this regulative network highlight their role in development and malignancy of B-cells.

Hodgkin lymphoma: an update on its biology with new insights into classification

In the past few years, there has been a greater understanding of the spectrum and biology of Hodgkin lymphoma (HL). In standard texts, HL is classified as 2 distinct entities, namely nodular lymphocyte-predominant HL and classical HL (CHL). However, recent evidence suggests that CHL is not a single disease. Although the mixed cellularity and lymphocyte-depleted subtypes might be part of a biologic continuum, the nodular sclerosis subtype has a distinct epidemiology, clinical presentation, and histology. Nodular sclerosis HL might also be related to primary mediastinal B-cell lymphoma and mediastinal gray-zone lymphomas. We present an update on the pathobiology of HL and discuss these biologic and clinical differences in this review.

Circulating clonotypic B cells in classic Hodgkin lymphoma

Although Hodgkin and Reed-Sternberg (HRS) cells are B lymphoid cells, they are unlike any normal cells of that lineage. Moreover, the limited proliferative potential of HRS cells belies the clinical aggressiveness of Hodgkin lymphoma (HL). More than 20 years ago, the L428 HL cell line was reported to contain a small population of phenotypic B cells that appeared responsible for the continued generation of HRS cells. This observation, however, has never been corroborated, and such clonotypic B cells have never been documented in HL patients. We found that both the L428 and KM-H2 HL cell lines contained rare B-cell subpopulations responsible for the generation and maintenance of the predominant HRS cell population. The B cells within the HL cell lines expressed immunoglobulin light chain, the memory B-cell antigen CD27, and the stem cell marker aldehyde dehydrogenase (ALDH). Clonal CD27(+)ALDH(high) B cells, sharing immunoglobulin gene rearrangements with lymph node HRS cells, were also detected in the blood of most newly diagnosed HL patients regardless of stage. Although the clinical significance of circulating clonotypic B cells in HL remains unclear, these data suggest they may be the initiating cells for HL.

Expression of bcl2 family proteins and active caspase 3 in classical Hodgkin's lymphomas

The expression of various bcl2 family proteins has been reported in Hodgkin and Reed-Sternberg cells, but the proteins bad, bid, and bim have not been analyzed in classical Hodgkin's lymphomas (HLs). This study aimed to investigate the expression of the proteins bcl2, bcl-xl, mcl1, bax, bak, bad, bid, bim, and active caspase 3, and the TUNEL (terminal deoxynucleotidyl transferase-mediated in situ labeling) index to gain further insight into the apoptosis profile of classical HLs. A high expression of the proteins bcl2, bcl-xl, mcl1, bax, bak, bad, bid, and bim in HRS cells was found in 27 of 101 (27%), 95 of 101 (94%), 27 of 97 (29%), 73 of 95 (77%), 37 of 102 (36%), 85 of 94 (90%), 19 of 109 (17%), and 43 of 91 (47%) cases, respectively. The high expression of bcl-xl, bax, and bad in HRS cells in most classical HLs indicates that these proteins may play predominant roles in the regulation of apoptosis in classical HLs. Active caspase 3-positive and TUNEL-positive Reed-Sternberg cells were detected in 47 of 70 (67%; range, 0%-12%) and 60 of 71 (85%; range, 0%-19%) cases, respectively. Significant positive correlations were found between bax/bcl2 (P = .002), bad/bcl2 (P = .020), bad/bcl-xl (P = .003), and bim/mcl1 (P = .036). Based on these findings, it could be hypothesized that the antiapoptotic proteins bcl2, bcl-xl, and mcl1 may counteract the expression of the proapoptotic proteins bax, bad, and bim, thereby contributing to the survival of Reed-Sternberg cells.

New transcription factors in diagnostic hematopathology

The transcription factors (TFs) that controls the intricate machinery of multistep differentiation and activation programs of the lymphoid system, represent a complex array of proteins, whose identification and function has only in part been completed. TFs are usually expressed during specific differentiation or activation cellular programs, making them interesting tools in diagnostic immunohistochemistry. In fact, the specificity of some of these TFs for lineage or activation/differentiation passages or their abnormal expression in specific disease entity, represents a feature that has been exploited in diagnostic/prognostic immunohistochemistry. Bcl-6 was the prototype of this class of markers. Currently, the expanding knowledge of the TFs involved in the differentiation programs and in the activation processes of T-lymphocyte and B-lymphocyte in normal and neoplastic conditions and the availability of antibodies able to efficiently recognize these TFs in histologic material, represent a powerful tool in diagnostic hematopathology. In this review we will consider the basic biologic aspects and the applications in hematopathology of some of the lymphocyte-related TFs, including Pax5/BSAB, MUM1/IRF4, BOB1, Oct-2, T-bet, and FOXP3. This field is rapidly evolving, as witnessed by the ongoing growing number of novel TFs with possible diagnostic applications appearing in the literature.

Expression of the human germinal center-associated lymphoma (HGAL) protein identifies a subset of classic Hodgkin lymphoma of germinal center derivation and improved survival

The human germinal-center-associated lymphoma (HGAL) gene and its cognate protein are expressed in a germinal center (GC)-specific manner. Its expression in classic Hodgkin lymphoma (cHL) prompted us to address whether HGAL expression could distinguish biologically distinct subgroups of cHL. Tissue microarrays from 145 patients treated with curative intent showed HGAL staining in 75% and was closely correlated with MUM1/IRF4 (92%) expression. BCL6 (26%), CD10 (0%), BCL2 (31%), Blimp1 (0.02%), and Epstein-Barr virus (EBV) (20%) showed no specific correlation; neither did phospho-STAT6, a key mediator of IL-4 and IL-13 signaling that induces HGAL and is implicated in cHL pathogenesis. In our study cohort, the 5-year overall survival (OS) correlated with young age (less than 45 years, P < .001), low stage (stage I and II, P = .04), and low International Prognostic Score (P = .002). In univariate analysis, HGAL expression was associated with improved OS (P = .01) and failure-free survival (FFS) (P = .05) but was not independent of other factors in multivariate analysis of OS or FFS. The expression of the GC-specific marker HGAL in a subset of cHL suggests that these cHLs retain characteristics of GC-derived lymphomas. The association with improved OS in univariate but not multivariate analysis suggests that HGAL expression is related to known clinical parameters of improved survival.

Composite recurrent hodgkin lymphoma and diffuse large B-cell lymphoma: one clone, two faces

We describe a composite lymphoma with recurrent Hodgkin lymphoma and diffuse large B-cell lymphoma components manifesting as a single, perforated small intestinal tumor in a 56-year-old man with a history of classical Hodgkin lymphoma and recent relapse in the bone marrow. The resected mass had 2 morphologically and immunophenotypically distinct components; 1 showed a pleomorphic cellular infiltrate with fibrosis and contained numerous, large Hodgkin/Reed-Sternberg-like cells and variants. The tumor cells were CD30+ and focally positive for CD15 but CD20-, CD79a-, and PAX-5-. In situ hybridization for Epstein-Barr virus (EBV) was strongly positive in the large pleomorphic tumor cells. The adjacent component displayed sheets of relatively uniform, large lymphoid cells with typical morphologic features of diffuse large cell lymphoma. The tumor cells showed uniform expression of tested B-cell antigens, absence of CD30 or CD15, and complete absence of EBV-encoded RNA. Separate molecular studies with immunoglobulin heavy and k light chain gene rearrangements clearly demonstrated an identical rearrangement pattern, indicating derivation from the same clone, which was confirmed by direct DNA sequencing analysis. Such distinctly different morphology, immunophenotype, and EBV status in different components within a clonally related single tumor mass is striking.