T-cell variant of classical Hodgkin's lymphoma with nodal and cutaneous manifestations demonstrated by single-cell polymerase chain reaction

Advances in Hodgkin lymphoma research

Hodgkin lymphoma (HL) has been and still is the most enigmatic lymphoid malignancy in humans. Since the first molecular analysis of isolated Hodgkin and Reed-Sternberg (HRS) tumor cells of classic HL 30 years ago, substantial advances in our understanding of HL have been made. This review describes the cellular origin of HL, summarizes the current knowledge about the genetic lesions in HRS cells, and highlights the role of Epstein-Barr virus (EBV) in HL pathogenesis. Moreover, the pathobiological roles of altered gene expression and deregulated signaling pathways are discussed and key aspects of the HL microenvironment are presented.

A significant proportion of classic Hodgkin lymphoma recurrences represents clonally unrelated second primary lymphoma

Despite high cure rates in classic Hodgkin lymphoma (cHL), relapses are observed. Whether relapsed cHL represents second primary lymphoma or an underlying T-cell lymphoma (TCL) mimicking cHL is underinvestigated. To analyze the nature of cHL recurrences, in-depth clonality testing of immunoglobulin (Ig) and T-cell receptor (TCR) rearrangements was performed in paired cHL diagnoses and recurrences among 60 patients, supported by targeted mutation analysis of lymphoma-associated genes. Clonal Ig rearrangements were detected by next-generation sequencing (NGS) in 69 of 120 (58%) diagnoses and recurrence samples. The clonal relationship could be established in 34 cases, identifying clonally related relapsed cHL in 24 of 34 patients (71%). Clonally unrelated cHL was observed in 10 of 34 patients (29%) as determined by IG-NGS clonality assessment and confirmed by the identification of predominantly mutually exclusive gene mutations in the paired cHL samples. In recurrences of >2 years, ∼60% of patients with cHL for whom the clonal relationship could be established showed a second primary cHL. Clonal TCR gene rearrangements were identified in 14 of 125 samples (11%), and TCL-associated gene mutations were detected in 7 of 14 samples. Retrospective pathology review with integration of the molecular findings were consistent with an underlying TCL in 5 patients aged >50 years. This study shows that cHL recurrences, especially after 2 years, sometimes represent a new primary cHL or TCL mimicking cHL, as uncovered by NGS-based Ig/TCR clonality testing and gene mutation analysis. Given the significant therapeutic consequences, molecular testing of a presumed relapse in cHL is crucial for subsequent appropriate treatment strategies adapted to the specific lymphoma presentation.

Plasticity in Classical Hodgkin Composite Lymphomas: A Systematic Review

The co-occurrence of several lymphomas in a patient defines composite/synchronous lymphoma. A common cellular origin has been reported for both contingents of such entities. In the present review, we aimed to gather the available data on composite lymphomas associating a classical Hodgkin lymphoma (cHL) with another lymphoma, to better understand the plasticity of mature B and T-cells. This review highlights that >70% of patients with a composite lymphoma are ≥55 years old, with a male predominance. The most reported associations are cHL with follicular lymphoma or diffuse large B-cell lymphoma, with over 130 cases reported. The cHL contingent is often of mixed cellularity type, with a more frequent focal/weak CD20 expression (30% to 55.6%) compared to de novo cHL, suggesting a particular pathophysiology. Moreover, Hodgkin cells may express specific markers of the associated lymphoma (e.g., BCL2/BCL6 for follicular lymphoma and Cyclin D1 for mantle cell lymphoma), sometimes combined with common BCL2/BCL6 or CCND1 rearrangements, respectively. In addition, both contingents may share similar IgH/IgK rearrangements and identical pathogenic variants, reinforcing the hypothesis of a common clonal origin. Finally, cHL appears to be endowed with a greater plasticity than previously thought, supporting a common clonal origin and a transdifferentiation process during lymphomagenesis of composite lymphomas.

Novel Approaches in Molecular Characterization of Classical Hodgkin Lymphoma

Simple Summary

The unique tumor composition of classical Hodgkin lymphoma (cHL), with only a small fraction of malignant Hodgkin and Reed–Sternberg cells within the tumor tissue, has created many challenges to characterize the genetic alterations that drive this lymphoid malignancy. Major advances in sequencing technologies and detailed analysis of circulating tumor DNA in blood samples of patients have provided important contributions to enhance our understanding of the pathogenesis of cHL. In this review, we provide an overview of the recent advances in genotyping the clonal and mutational landscape of cHL. In addition, we discuss different next-generation sequencing applications to characterize tumor tissue and cell-free DNA, which are now available to improve the diagnosis of cHL, and to monitor therapeutic response or disease progression during treatment and follow up of cHL patients.

Abstract

Classical Hodgkin lymphoma (cHL) represents a B-cell lymphoproliferative disease characterized by clonal immunoglobulin gene rearrangements and recurrent genomic aberrations in the Hodgkin Reed–Sternberg cells in a reactive inflammatory background. Several methods are available for the molecular analysis of cHL on both tissue and cell-free DNA isolated from blood, which can provide detailed information regarding the clonal composition and genetic alterations that drive lymphoma pathogenesis. Clonality testing involving the detection of immunoglobulin and T cell receptor gene rearrangements, together with mutation analysis, represent valuable tools for cHL diagnostics, especially for patients with an atypical histological or clinical presentation reminiscent of a reactive lesion or another lymphoma subtype. In addition, clonality assessment may establish the clonal relationship of composite or subsequent lymphoma presentations within one patient. During the last few decades, more insight has been obtained on the molecular mechanisms that drive cHL development, including recurrently affected signaling pathways (e.g., NF-κB and JAK/STAT) and immune evasion. We provide an overview of the different approaches to characterize the molecular composition of cHL, and the implementation of these next-generation sequencing-based techniques in research and diagnostic settings.

Nodal involvement by cutaneous CD30-positive T-cell lymphoma mimicking classical Hodgkin lymphoma

An association between classical Hodgkin lymphoma (cHL) and mycosis fungoides (MF) or lymphomatoid papulosis has been reported in the literature. However, there can be considerable morphologic and immunophenotypic overlap between cHL and nodal involvement by CD30-positive T-cell lymphoproliferative disorders (CD30-T-LPD). To examine this potential association, biopsies from patients with a history of MF or primary cutaneous CD30-T-LPD and lymph node biopsies reported as either CD30-positive T-cell lymphoma (TCL) with Hodgkin-like cells or cHL were retrieved from the authors' institution. Of 11 cases identified, 10 were considered CD30-positive TCL with Hodgkin-like cells, whereas 1 was confirmed as cHL upon review. Five cases originally diagnosed as cHL were revised as CD30-positive TCL. Cases of CD30-positive TCL with Hodgkin-like cells showed a male predominance (M:F, 4:1) with a median age of 53 years (range, 44 to 72 y). Nearly all patients (9/10) initially presented with skin lesions. In 7/10 patients the draining lymph node was involved, whereas in 3 cases this could not be confirmed. Tumor cells morphologically resembled Hodgkin/Reed-Sternberg cells; they were uniformly strongly positive for CD30, and CD15 was expressed in 9/10 (90%) cases. A T-cell derivation was confirmed by T-cell antigen expression (7/10) and clonal rearrangement of T-cell receptor genes (9/10). In 3 cases a common T-cell clone was identified in skin and lymph node. B-cell markers (CD20/PAX5) were consistently negative. In 1 case the diagnosis of cHL followed by lymphomatoid papulosis was confirmed, with Hodgkin/Reed-Sternberg cells expressing PAX5, CD30, and CD15. In situ hybridization studies for Epstein Barr virus were negative. We show that cHL is less often associated with MF and primary cutaneous CD30-T-LPD than previously thought and that the coexpression of CD30 and CD15 in these TCLs may lead to a mistaken diagnosis of cHL.

Vitamin D3 receptor is highly expressed in Hodgkin's lymphoma

Background

Hodgkin lymphoma (HL) is one of the most frequent lymphoma in the western world. Despite a good overall prognosis, some patients suffer relapsing tumors which are difficult to cure. Over a long period Vitamin D has been shown to be a potential treatment for cancer. Vitamin D acts via the vitamin D receptor, a nuclear receptor, acting as an inducible transcription factor. We aimed to investigate the expression of vitamin D receptor as a possible diagnostic marker and potential therapeutic target in HL as well as in B-cell derived non-Hodgkin lymphoma (B-NHL).

Methods

We used a panel of 193 formalin fixed tissues of lymphoma cases consisting of 55 cases of HL and 138 cases on several B-NHL entities.

Results

Vitamin D receptor is strongly expressed in tumor cells of HL, regardless of the sub entity with an overall positivity of 80% of all HL cases. In contrast, only about 17% of the analyzed origin-NHL showed positivity for vitamin D receptor. The detection of nuclear localization of vitamin D receptor in the tumor cells of HL suggests activated status of the vitamin D receptor.

Conclusions

Our study suggests VDR as a specific marker for tumor cells of HL, but not of B-NHL subtypes. Further, the observed nuclear localization suggests an activated receptor status in tumor cells of HL. Further investigations of mutational status and functional studies may shed some light in functional relevance of vitamin D receptor signaling in HL.

JAK2 rearrangements, including the novel SEC31A-JAK2 fusion, are recurrent in classical Hodgkin lymphoma

The genetics of classical Hodgkin lymphoma (cHL) is poorly understood. The finding of a JAK2-involving t(4;9)(q21;p24) in 1 case of cHL prompted us to characterize this translocation on a molecular level and to determine the prevalence of JAK2 rearrangements in cHL. We showed that the t(4;9)(q21;p24) leads to a novel SEC31A-JAK2 fusion. Screening of 131 cHL cases identified 1 additional case with SEC31A-JAK2 and 2 additional cases with rearrangements involving JAK2. We demonstrated that SEC31A-JAK2 is oncogenic in vitro and acts as a constitutively activated tyrosine kinase that is sensitive to JAK inhibitors. In vivo, SEC31A-JAK2 was found to induce a T-lymphoblastic lymphoma or myeloid phenotype in a murine bone marrow transplantation model. Altogether, we identified SEC31A-JAK2 as a chromosomal aberration characteristic for cHL and provide evidence that JAK2 rearrangements occur in a minority of cHL cases. Given the proven oncogenic potential of this novel fusion, our studies provide new insights into the pathogenesis of cHL and indicate that in at least some cases, constitutive activation of the JAK/STAT pathway is caused by JAK2 rearrangements. The finding that SEC31A-JAK2 responds to JAK inhibitors indicates that patients with cHL and JAK2 rearrangements may benefit from targeted therapies.

Pathogenesis of classical and lymphocyte-predominant Hodgkin lymphoma

Hodgkin and Reed-Sternberg (HRS) cells in classical Hodgkin lymphoma (HL) and lymphocytic and histiocytic (L&H) cells in nodular lymphocyte-predominant HL (NLPHL) are derived from germinal-center B cells. HRS cells have, however, largely lost their B cell phenotype and aberrantly express markers and transcriptional regulators of other hematolymphoid cell types. Deregulation of multiple signaling pathways and downstream transcription factors, including receptor tyrosine kinases, nuclear factor-kappa B (NF-kappaB), and Janus kinase/signal transducer and activator of transcription (JAK/STAT), is a further hallmark of HRS cells. These cells harbor genetic lesions that contribute to or cause increases in the activity of transcription factors of the NF-kappaB and STAT families. HRS cells are found within a mixed reactive cellular infiltrate and interact with these nonmalignant cells in a complex fashion that appears to be essential for HRS cell survival and proliferation. Less is known about the pathogenesis of L&H cells in NLPHL, but increases in the activity of receptor tyrosine kinases, NF-kappaB, and JAK/STAT have also been detected.

The biology of Hodgkin's lymphoma

Hodgkin's lymphoma was first described in 1832. The aetiology of this lymphoma, however, remained enigmatic for a long time. Only within the past 10 years has the B-cell nature of the pathognomonic Hodgkin and Reed-Sternberg (HRS) cells been revealed, along with several recurrent genetic lesions. The pathogenetic role for Epstein-Barr virus infection has also been substantiated. HRS cells in classical Hodgkin's lymphoma have several characteristics that are unusual for lymphoid tumour cells, and the Hodgkin's lymphoma microenvironment is dominated by an extensive mixed, potentially inflammatory cellular infiltrate. Understanding the contribution of all of these changes to the pathogenesis of this disease is essential for the development of novel therapies.

Identification of candidate tumour suppressor gene loci for Hodgkin and Reed-Sternberg cells by characterisation of homozygous deletions in classical Hodgkin lymphoma cell lines

Several tumour suppressor genes (TSG) have been identified as a result of mapping homozygous deletions in cancer cells. To identify putative TSG involved in the pathogenesis of classical Hodgkin lymphoma (cHL), we investigated four cHL cell lines (L428, HDLM2, KMH2, L1236) using four different array-Comparative Genomic Hybridisation (array-CGH) platforms and focused on high resolution identification of homozygous deletions. Out of 79 candidate regions of bi-allelic loss identified by array-CGH, besides previously described regions, 28 novel regions of homozygous deletions could be verified by polymerase chain reaction. These regions ranged from 13 kb to 619 kb in size. Eleven of the 28 novel bi-allelic losses were putative copy number polymorphisms. This left 17 regions that might harbour novel tumour suppressors involved in Hodgkin lymphoma. Expression profiling with two different platforms confirmed lack of expression of the majority of the genes located in the homozygous deletions. Furthermore, analysis of ontology annotations of genes located in the homozygously deleted regions indicated an enrichment of genes involved in apoptosis and cell death. In summary, through the mapping of homozygous deletions in cell lines this study identified a series of genes, such as SEPT9, GNG7 and CYBB, which might encode candidate tumour suppressors involved in the pathogenesis of cHL.

Gene rearrangement and comparative genomic hybridization studies of classic Hodgkin lymphoma expressing T-cell antigens

CONTEXT

Reed-Sternberg cells in classic Hodgkin lymphoma are enigmatic and difficult to study because they are so sparse. Tissue microdissection allows for the isolation of single Reed-Sternberg cells. Isolated Reed-Sternberg cells show clonal immunoglobulin gene rearrangement indicating a B-cell origin. Rarely, Reed-Sternberg cells in classic Hodgkin lymphoma express T-cell antigens, suggesting a possible T-cell origin.

OBJECTIVE

To determine whether there is a difference in genotype between classic Hodgkin lymphoma and classic Hodgkin lymphoma expressing T-cell antigens and to document T-cell clonality.

DESIGN

We studied 4 cases of Hodgkin lymphoma with a characteristic phenotype and immunoreactivity for CD2 and CD3. Single CD30+ Reed-Sternberg cells from each case were isolated by laser capture microdissection for immunoglobulin heavy chain and T-cell receptor-gamma genes by polymerase chain reaction studies. Comparative genomic hybridization was performed in all cases.

RESULTS

Two of 4 cases showed clonal rearrangement of the T-cell receptor-gamma; none showed immunoglobulin heavy chain rearrangement. Two control cases were negative for T cell receptor-gamma but 1 showed immunoglobulin heavy chain rearrangement. Comparative genomic hybridization analysis revealed significant overlap in genomic alteration in Hodgkin lymphoma cases regardless of genotype or phenotype and several regions of imbalance specific to CD3+ Hodgkin lymphoma cases. All patients are alive with no evidence of disease from 10 to 44 months.

CONCLUSIONS

Our findings suggest that a T-cell phenotype classic Hodgkin lymphoma can be supported by genotypic studies and that there may be cytogenetic differences between classic Hodgkin lymphoma and Hodgkin lymphoma expressing T-cell antigens.

Primary Cutaneous Lymphoproliferative Disorders With Dual Lineage Rearrangement

We present a series of 15 cases of cutaneous lymphoma and pseudolymphoma with dual lineage rearrangement identified among approximately 1200 cases of cutaneous lymphoproliferative disorders assessed in our 4 institutions during the last 8 years in which the results of both T-cell receptor and immunoglobulin heavy chain rearrangement investigations were available. On the basis of the clinicopathologic information, the cases were retrospectively subdivided into 2 categories: (1) cases with definite features of cutaneous lymphoma or pseudolymphoma (n = 11) and (2) cases with unclassifiable disease (n = 4). The detection of dual genotype in the first group did not influence the final diagnosis; 7 cases represented cutaneous B-cell lymphomas, 3 pseudolymphomas, and 1 case lymphomatoid papulosis. The presence of monoclonal T-cell receptor-gene rearrangements in these cases may be explained either by monoclonal or oligoclonal expansion of exuberant T cells (or B cells in case of lymphomatoid papulosis) or by lineage infidelity. Three patients with unclassifiable disease had several clinical and histopathologic features in common. They were elderly, presented with solitary lesions, were in good general health and histopathologically demonstrated a dense multinodular infiltrate containing approximately an equal number of T and B cells and a high number of histiocytes forming granulomas, with prominent granulomatous features in 2 cases. B cells were either scattered with the infiltrate or formed collections vaguely resembling follicles; Reed-Sternberg-like cells were seen in 2 cases. B cells showed expression neither of immunoglobulin light chain. The T-cell component was represented mainly by small, well-differentiated lymphocytes or slightly pleomorphic cells, with some medium-sized convoluted cells. Epstein-Barr virus was not detected by polymerase chain reaction. The exact classification of these cases is unknown; they differ histopathologically from previously published cases of bigenotypic cutaneous lymphomas. They may merely represent a growth or reactive pattern, but, on the other hand, may be low-grade lymphomas. If so, they may be histopathologically related to cutaneous Hodgkin disease, T-cell/histiocyte-rich large B-cell lymphoma, or composite lymphomas. Further reports are needed to identify these lesions to clarify their nature and biologic potential.

Molecular biology of Hodgkin's and Reed/Sternberg cells in Hodgkin's lymphoma

Hodgkin's and Reed/Sternberg (HRS) cells, the tumour cells in classical Hodgkin's lymphoma (HL), represent transformed B cells in nearly all cases. The detection of destructive somatic mutations in the rearranged immunoglobulin (Ig) genes of HRS cells in classical HL indicated that they originate from preapoptotic germinal centre (GC) B cells that lost the capacity to express a high-affinity B-cell receptor (BCR). Several aberrantly activated signalling pathways and transcription factors have been identified that contribute to the rescue of HRS cells from apoptosis. Among the deregulated signalling pathways, activation of multiple receptor tyrosine kinases in HRS cells appears to be a specific feature of HL. In about 40% of cases of classical HL the HRS cells are infected by Epstein-Barr virus (EBV), indicating an important role of EBV in HL pathogenesis. Interestingly, nearly all cases of HL with destructive Ig gene mutations eliminating BCR expression (e.g. nonsense mutations) are EBV-positive, suggesting that EBV-encoded genes have a particular function to prevent apoptosis of HRS-cell precursors that acquired such crippling mutations. This idea is further supported by the recent demonstration that isolated human GC B cells harbouring crippled Ig genes can be rescued by EBV from cell death, giving rise to lymphoblastoid cell lines. The molecular analysis of composite Hodgkin's and non-Hodgkin's lymphomas indicated that many cases develop from a common GC B-cell precursor in a multistep transformation process with both shared and distinct oncogenic events.

Pathobiology of CD30+ cutaneous T-cell lymphomas

CD30+ cutaneous lymphoproliferative disorders include lymphomatoid papulosis (LyP) and anaplastic large cell lymphoma (ALCL). LyP is associated with development of lymphoma in nearly 20% of patients. Herein is reviewed the clonal relationship of LyP to malignant lymphoma, the concept of a common stem cell for LyP and associated lymphomas, and the role of genetic instability in lymphomagenesis. The possible role of the CD30+ cell as a regulatory T-cell is introduced and a model for progression of LyP to ALCL is illustrated.

Cutaneous T cell lymphoma and classic Hodgkin lymphoma of the B cell type within a single lymph node: composite lymphoma

Composite lymphomas are defined as two unrelated, morphologically and genetically distinct lymphomas occurring at the same point in time within the same tissue or organ. Since their original definition, several composite lymphomas have been reported exclusively based on morphological grounds. However, with the application of immunohistological and molecular biological techniques it has become evident that many so called "composite" lymphomas do not fulfil the necessary criteria, because they merely represent two different morphological phenotypes of the same malignant clone. This report describes the manifestation of a true composite lymphoma within a single cervical lymph node, which is composed of a cutaneous T cell lymphoma and a classic Hodgkin lymphoma of B cell type--a very rare finding indeed.

Systemic and primary cutaneous anaplastic large cell lymphomas

Anaplastic large cell lymphoma (ALCL) is a neoplasm of activated lymphocytes, commonly expressing T-cell antigens and cytotoxic proteins. Histopathology reveals distinctive infiltration of sinuses and paracortical T-cell-rich regions of lymph nodes by tumor cells which have abundant cytoplasm and large irregular/convoluted nuclei, and which are frequently multinucleated with prominent nucleoli. ALCL often presents in advanced clinical stages with B symptoms; extranodal disease occurs in 40% of patients. The pathogenesis of systemic ALCL is linked to phosphorylation of a tyrosine kinase (ALK) resulting in unregulated growth of affected lymphoid cells. ALK is activated through chromosomal translocations/inversions with any of several partner genes, most commonly nucleophosmin (NPM). Downstream signal transduction pathway(s) are not fully defined but appear to involve phospholipase Cgamma, phosphatidylinositol (PI)3K/Akt, and STAT-3 and STAT-5 proteins. Primary cutaneous ALCL appears to have a different pathogenesis and better prognosis than does systemic ALCL, presenting as one or more skin tumors, usually localized. Excision or local irradiation is usually effective treatment. A clinically benign variant of primary cutaneous ALCL is lymphomatoid papulosis (LyP), characterized by recurrent crops of papules/nodules up to 2 cm in diameter which undergo spontaneous regression. LyP is managed by observation, ultraviolet light therapy, or low-dose methotrexate. LyP patients have a predisposition to develop malignant lymphomas, including Hodgkin's lymphoma, mycosis fungoides, and non-Hodgkin's lymphoma, by as yet unknown mechanisms. The prognosis for patients with LyP is otherwise excellent.

Identification of Hodgkin and Reed-Sternberg cell-specific genes by gene expression profiling

Hodgkin lymphoma (HL) is a malignancy of unknown pathogenesis. The malignant Hodgkin and Reed/Sternberg (HRS) cells derive from germinal center B cells (or rarely, T cells) but have a heterogeneous and largely uncharacterized phenotype. Using microarrays, we compared the gene expression profile of four HL cell lines with profiles of the main B cell subsets and B cell non-HLs to find out whether HRS cells, despite their described heterogeneity, show a distinct gene expression, to study their relationship to other normal and malignant B cells, and to identify genes aberrantly or overexpressed by HRS cells. The HL lines indeed clustered as a distinct entity, irrespective of their B or T cell derivation, and their gene expression was most similar to that of EBV-transformed B cells and cell lines derived from diffuse large cell lymphomas showing features of in vitro-activated B cells. Twenty-seven genes, most of which were previously unknown to be expressed by HRS cells, showed aberrant expression specifically in these cells, e.g., the transcription factors GATA-3, ABF1, EAR3, and Nrf3. For five genes, expression in primary HRS cells was confirmed. The newly identified HL-specific genes may play important roles in the pathogenesis of HL, potentially represent novel diagnostic markers, and can be considered for therapeutic targeting.