Lymphocyte predominance Hodgkin's disease: the use of bcl-6 and CD57 in diagnosis and differential diagnosis

Lymphocyte predominant cells of nodular lymphocyte predominant Hodgkin lymphoma interact with rosetting T cells in an immunological synapse

Nodular lymphocyte predominant Hodgkin lymphoma (NLPHL) is a subtype of Hodgkin lymphoma with a preserved B-cell phenotype and follicular T helper (T_FH ) cells rosetting around the tumor cells, the lymphocyte-predominant (LP) cells. As we recently described reactivity of the B-cell receptors of LP cells of some NLPHL cases with Moraxella spp. proteins, we hypothesized that LP cells could present peptides to rosetting T cells in a major histocompatibility complex class II (MHCII)-bound manner. Rosetting PD1⁺ T cells were present in the majority of NLPHL cases, both in typical (17/20) and variant patterns (16/19). In most cases, T-cell rosettes were CD69⁺ (typical NLPHL, 17/20; NLPHL variant, 14/19). Furthermore, both MHCII alpha and beta chains were expressed in the LP cells in 23/39 NLPHL. Proximity ligation assay and confocal laser imaging demonstrated interaction of the MHCII beta chain expressed by the LP cells and the T-cell receptor alpha chain expressed by rosetting T cells. We thus conclude that rosetting T cells in NLPHL express markers that are encountered after antigenic exposure, that MHCII is expressed by the LP cells, and that LP cells interact with rosetting T cells in an immunological synapse in a subset of cases. As they likely receive growth stimulatory signals in this way, blockade of this interaction, for example, by PD1-directed checkpoint inhibitors, could be a treatment option in a subset of cases in the future.

Diagnostic Utility of Flow Cytometry Analysis of Reactive T Cells in Nodular Lymphocyte-Predominant Hodgkin Lymphoma

OBJECTIVES

This study aims to define the diagnostic utility of flow cytometric features of T cells in nodular lymphocyte-predominant Hodgkin lymphoma (NLPHL).

METHODS

Cases were retrospectively identified based on diagnosis with NLPHL (n = 30 samples), classic Hodgkin lymphoma (CHL; n = 33), and reactive lymphoid hyperplasia (RLH; n = 43). Pathology slides were reviewed. Flow cytometry list mode data were reanalyzed.

RESULTS

The mean proportion of CD4 + CD8 + T cells (8.4%) in cases of NLPHL was significantly higher than seen in CHL (1.0%) or RLH (0.6%). Of the T cells, 28.4% were CD57 + in NLPHL, significantly higher (P < .05) than in CHL (3.2%) or RLH (3.2%). Based on receiver operating characteristic curve analysis, when using a cutoff of 3.0% of CD4 + CD8 + T cells, the diagnostic sensitivity for NLPHL is 83.3% with a specificity of 97.4%. The diagnostic sensitivity was 96.7% with a specificity of 98.7% when using a cutoff of 12% for CD57 + T cells.

CONCLUSIONS

Increased portions of CD57 + T cells and CD4 + CD8 + T cells are highly suggestive of the possibility of NLPHL. In addition, NLPHL diagnosis appears unlikely if neither CD57 + T cells nor CD4 + CD8 + T cells are increased. Future prospective studies including cases of progressive transformation of germinal center and T-cell/histiocyte-rich large B-cell lymphoma will further define the utility of flow cytometry of T cells in NLPHL.

CD57+ T-cells are a subpopulation of T-follicular helper cells in nodular lymphocyte predominant Hodgkin lymphoma

Background

Nodular lymphocyte predominant Hodgkin lymphoma (NLPHL) is characterized by lymphocyte-predominant (LP) cells in a background of CD4+ CD57+ T-cells. These cells are normally present in the germinal center of lymphoid tissues. The cells rosetting LP cells are described to be PD-1 and BCL-6 positive, which are markers of T-follicular helper cells. This study was designed to address the question: are the CD57+ T cells in germinal centers of tonsil and NLPHL TFH cells?

Results

Immunohistochemistry was performed on tonsil and NLPHL. For tonsil, cells per germinal center and for NLPHL, the area around LP cells was counted. Cells rosetting LP cells were also determined. In addition, flowcytometry was performed on cell suspensions. Cells directly rosetting LP cells are positive for CD57 and/or for two markers of T-follicular helper (TFH) cells, PD-1 and BCL-6. We show that in both tonsil and NLPHL more than 90 % of CD57+ T-cells are also positive for PD-1, whereas roughly half of the PD-1+ T-cells are CD57+. CD57+ cells co-express BCL-6 in tonsil and in the rosetting cells of NLPHL.

Conclusions

We conclude that CD57+ T-cells are TFH cells and form a subpopulation of TFH cells in tonsils and NLPHL.

Lymphocyte-Rich Classical Hodgkin Lymphoma. A Case with Difficulty in Distinguishing from Nodular Lymphocyte-Predominant Hodgkin Lymphoma

A 35-year-old man was referred to our hospital because of left supraclavicular and cervical lymphadenopathies. Histopathological examination of the lymph nodes revealed reactive lymphadenopathy. He visited our hospital three years after the initial diagnosis because of enlarged left cervical lymph nodes. Histopathologically, both Hodgkin/Reed-Sternberg (H/RS) and lymphocyte-predominant (LP) cells were found in the lymph node. We first suspected nodular lymphocyte-predominant Hodgkin lymphoma (NLPHL), because these cells were CD15(-) and CD30(-). However, the diagnosis of lymphocyte-rich classical Hodgkin lymphoma (LRCHL) was finally confirmed, because these cells were found to be CD20(-), Bob.1(+), Oct.2(-), and BCL6(-) by additional immunostaining. The patient was treated with six cycles of ABVD chemotherapy, and a complete response was achieved. However, he underwent autologous stem-cell transplantation after high-dose chemotherapy owing to a relapse 10 months after primary treatment. Distingushing LRCHL from NLPHL was difficult in this patient, because histopathological examination showed both H/RS and LP cells, and immunostaining revealed these cells to be triple negative (CD15(-), CD30(-) and CD20(-)). Accumulation of such cases are necessary to establish better criteria for the differential diagnosis and assessment of clinical behavior.

The role of inflammation in lymphoma

Human lymphomas usually develop in specialized tissue microenvironments characterized by different populations of accessory stromal and lymphoid cells that interact with malignant cells. A clinical role of the tumor microenvironment has recently emerged, bringing new knowledge and suggesting new ideas and targets for treatment. This chapter analyzes the microenvironment in human lymphomas highlighting the role of inflammation in their pathogenesis. Microenvironmental specificity is detailed according to different models including classic Hodgkin lymphoma (HL), follicular lymphoma (FL), diffuse large B-cell lymphoma (DLBCL), peripheral T-cell lymphoma, unspecified and angioimmunoblastic T-cell lymphoma (AITL).

Nodular lymphocyte predominant hodgkin lymphoma and T cell/histiocyte rich large B cell lymphoma--endpoints of a spectrum of one disease?

In contrast to the commonly indolent clinical behavior of nodular lymphocyte predominant Hodgkin lymphoma (NLPHL), T cell/histiocyte rich large B cell lymphoma (THRLBCL) is frequently diagnosed in advanced clinical stages and has a poor prognosis. Besides the different clinical presentations of these lymphoma entities, there are variants of NLPHL with considerable histopathologic overlap compared to THRLBCL. Especially THRLBCL-like NLPHL, a diffuse form of NLPHL, often presents a histopathologic pattern similar to THRLBCL, suggesting a close relationship between both lymphoma entities. To corroborate this hypothesis, we performed gene expression profiling of microdissected tumor cells of NLPHL, THRLBCL-like NLPHL and THRLBCL. In unsupervised analyses, the lymphomas did not cluster according to their entity. Moreover, even in supervised analyses, very few consistently differentially expressed transcripts were found, and for these genes the extent of differential expression was only moderate. Hence, there are no clear and consistent differences in the gene expression of the tumor cells of NLPHL, THRLBCL-like NLPHL and THRLBCL. Based on the gene expression studies, we identified BAT3/BAG6, HIGD1A, and FAT10/UBD as immunohistochemical markers expressed in the tumor cells of all three lymphomas. Characterization of the tumor microenvironment for infiltrating T cells and histiocytes revealed significant differences in the cellular composition between typical NLPHL and THRLBCL cases. However, THRLBCL-like NLPHL presented a histopathologic pattern more related to THRLBCL than NLPHL. In conclusion, NLPHL and THRLBCL may represent a spectrum of the same disease. The different clinical behavior of these lymphomas may be strongly influenced by differences in the lymphoma microenvironment, possibly related to the immune status of the patient at the timepoint of diagnosis.

The role of CD40/CD40L and interferon regulatory factor 4 in Hodgkin lymphoma microenvironment

Inflammation and cancer are two independent biological events that can play an interdependent role. The model of such interaction is represented by Hodgkin lymphoma (HL), where the microenvironment is dominated by an extensive mixed, potentially cellular inflammatory infiltrate that plays a decisive role in the pathobiology of HL. In this review we summarize updated information on the complex interactions between Hodgkin Reed-Sternberg (HRS) cells and their tissue microenvironment, highlighting the functional role of CD40/CD40L and interferon regulatory factor 4 (IRF4).

Hodgkin's Lymphomas: A Tumor Recognized by Its Microenvironment

Thomas Hodgkin's and Samuel Wilks first recognized Hodgkin disease in the first half of the 19th century. Initially described as lymphogranulomatosis, it was later recognized to be a lymphoid neoplasm derived from B cells and was classified on the basis of its histopathological features. Hodgkin lymphomas are now regarded as encompassing two clearly defined entities according to the WHO classification: nodular lymphocyte-predominant Hodgkin Lymphoma (NLPHL) and classical Hodgkin Lymphoma (CHL). This paper focuses on the current knowledge about the biological features that characterize both NLPHL and CHL, highlighting those relevant to correct pathological diagnosis and those that might be associated with patient outcome.

Programmed death 1 expression in variant immunoarchitectural patterns of nodular lymphocyte predominant Hodgkin lymphoma: comparison with CD57 and lymphomas in the differential diagnosis

Recent studies have exploited an antibody directed against programmed death 1 expressed by follicular helper T-cells in the diagnosis of nodular lymphocyte predominant Hodgkin lymphoma. We had previously described clinically relevant, variant immunoarchitectural patterns of nodular lymphocyte predominant Hodgkin lymphoma and, in this study, sought to address the diagnostic utility of programmed death 1 in comparison with CD57 in variant nodular lymphocyte predominant Hodgkin lymphoma. Immunohistologic staining for programmed death 1 was carried out on biopsies of 67 patients with variant nodular lymphocyte predominant Hodgkin lymphoma. Thirty-four additional cases of nodular lymphocyte predominant Hodgkin lymphoma with associated diffuse areas, de novo T-cell and histiocyte-rich large B-cell lymphoma, and lymphocyte-rich classic Hodgkin lymphoma were also studied. Our results show that programmed death 1 positivity was found in the majority of nodular lymphocyte predominant Hodgkin lymphoma cases with a classic nodular architecture (87%) as compared with 50% for CD57 and was particularly helpful in identifying extranodular large atypical cells. Nodular lymphocyte predominant Hodgkin lymphoma with diffuse areas showed a gradual decrease in programmed death 1 reactivity from nodular to diffuse areas, although a significant proportion (40%-50%) of cases retained programmed death 1 positivity also in diffuse areas. In addition, T-cell and histiocyte-rich large B-cell lymphoma and lymphocyte-rich classic Hodgkin lymphoma displayed programmed death 1 positivity in a significant subset of cases (33%-40%). In conclusion, our study supports the utility of programmed death 1 in the diagnosis of nodular lymphocyte predominant Hodgkin lymphoma and shows greater sensitivity of staining of programmed death 1 as compared with CD57 across all variants of nodular lymphocyte predominant Hodgkin lymphoma. Loss of programmed death 1 reactivity did not correlate with diffuse areas, progression, or the ability to differentiate nodular lymphocyte predominant Hodgkin lymphoma from T-cell and histiocyte-rich large B-cell lymphoma. These findings suggest the need for continued vigilance in the diagnosis of nodular lymphocyte predominant Hodgkin lymphoma and its immunoarchitectural variants as well as related lymphomas in their differential diagnosis.

CD57+ T lymphocytes and functional immune deficiency

CD57(+) expression in T lymphocytes has been recognized for decades as a marker of in vitro replicative senescence. In recent years, accumulating evidences have pointed on the utility of this marker to measure functional immune deficiency in patients with autoimmune disease, infectious diseases, and cancers. We review here the relevant literature and implications in clinical settings.

Atypical lymphoid hyperplasia mimicking lymphoma

The distinction between reactive and neoplastic lymphoid infiltrates is a common problem in clinical practice and can be problematic. The clinical implications for both the patient and the treating clinician are profound. In this article, we discuss six of the common entities that can present as atypical lymphoid hyperplasia and thus can mimic malignant lymphomas, with emphasis on morphologic features, immunophenotypic findings, and molecular correlates that help distinguish these disorders from neoplastic conditions. The six conditions to be discussed in detail include reactive follicular hyperplasia versus follicular lymphoma; progressive transformation of germinal centers versus nodular lymphocyte predominant Hodgkin lymphoma; immunoblastic proliferations versus diffuse large B-cell lymphomas; variant forms of Castleman disease that may mimic a number of lymphoid cancers; Kikuchi's disease versus large cell lymphomas; and finally, dermatopathic lymphadenopathy and its distinction from lymph nodes showing early involvement by cutaneous T-cell lymphoma (Mycosis fungoides).

Lymphocyte-rich classical Hodgkin's lymphoma: distinctive tumor and microenvironment markers

The existence, diagnostic features, and the biological and clinical relevance of lymphocyte-rich classical Hodgkin's lymphoma remain controversial. A comparative marker analysis of lymphocyte-rich classical Hodgkin's lymphoma, nodular lymphocyte-predominance Hodgkin's lymphoma, and of other subtypes of classical Hodgkin's lymphoma was carried out. Markers were selected focusing on B-cell lineage and transcription program (OCT.1, OCT.2, BOB.1, BCL6, PAX-5, GCET1, KLHL6, and BLIMP1), the NF-kappaB signaling pathway (REL-B, C-REL, TRAF-1, p-50, and MUM-1) and the T-cell microenvironment (CD3, CD57, PD-1, CXCL-13, and CD10, BCL-6, CD23). Lymphocyte-rich classical Hodgkin's lymphoma cases displayed features intermediate between those of classical Hodgkin's lymphoma and nodular lymphocyte-predominance Hodgkin's lymphoma. The expression of B-cell transcription factors such as OCT.1, OCT.2, BOB.1, and BCL6 was more frequent in lymphocyte-rich classical Hodgkin's lymphoma than in classical Hodgkin's lymphoma. A follicular T-cell microenvironment was also identified in 50% of lymphocyte-rich classical Hodgkin's lymphoma cases. NF-kB markers were expressed at frequencies comparable with those observed in classical Hodgkin's lymphoma. The neoplastic cell immunophenotype and microenvironment in lymphocyte-rich classical Hodgkin's lymphoma closely mimic that which are observed in the outer zone of the germinal center, where B-cell blasts with germinal-center markers co-express CD30 and the B-cell transcription program, surrounded by follicular T-cell rosettes. Lymphocyte-rich classical Hodgkin's lymphoma seems to be characterized by a stronger expression of the B-cell transcription program by the neoplastic cells and by a follicular T-cell background, occupying an intermediate position between classical Hodgkin's lymphoma and nodular lymphocyte-predominance Hodgkin's lymphoma.

Differentiating germinal center-derived lymphomas through their cellular microenvironment

Recent studies on normal and malignant B-cells have provided evidence that the germinal center (GC) of lymphoid follicles exerts a role in B-cell physiology and malignancy. GC-derived lymphomas include both B-cell and T-cell lymphomas. Remarkably, tumor cells of GC-derived lymphomas proliferate in close association with cellular environment that retains key features of normal GC cellular microenvironment. Neoplastic follicles in follicular lymphoma contain, in addition to follicular dendritic cells (FDC) other non-neoplastic cells including macrophages and GC T-cells. In addition to aggregates of FDCs, the background infiltrate of nodular lymphocyte predominant Hodgkin lymphoma includes small B-cells, T-cells, and histiocytes. Typically, most of the lymphocyte predominant (LP) cells are ringed by CD3+/CD4+ T-cells expressing CD57, PD1, BCL6, and MUM1/IRF4. By contrast, Reed-Sternberg cells of classic Hodgkin lymphoma (cHL) are surrounded by CD3+/CD4+ T-cells expressing CD40L. Unlike cHL and other peripheral T-cell lymphomas, the AITL microenvironment characteristically contain a prominent proliferation of high endothelial venules and FDC. Thus, these findings shed new light on the characterization of GC-derived lymphomas and may help in the differential diagnosis and acknowledge several novel pathogenetic mechanisms on these lymphomas. Am. J. Hematol., 2009. (c) 2009 Wiley-Liss, Inc.

Sacral intraspinal extradural primitive neuroectodermal tumor

BACKGROUND CONTEXT

Intraspinal primitive neuroectodermal tumors (PNETs) are an exceedingly rare entity. A recent literature research revealed 28 cases reported. Only a few tumors in the literature were extradural in location, in the cervical and thoracic spine. The average survival after combination treatment including chemotherapy, radiation, and surgical resection is 20 months for the cases reported in the literature.

PURPOSE

We report a case of a patient with sciatica and cauda equine-like symptoms.

STUDY DESIGN

Case report.

METHODS

Urgent sacral decompression and resection of the tumor was performed with rapid pain relief for the patient.

RESULTS

Histology revealed a sacral extradural small blue-cell tumor, consistent with ES/PNET family tumors. An oncological workup revealed that the tumor presentation was metastatic with pulmonary and abdominal nodules. The patient underwent combination chemotherapy with vincristine, doxorubicin, and cyclophosphamide with mesna for 4 months.

CONCLUSIONS

The patient was without disease after excision, two courses of 4-month chemotherapy, and one course of 5-week radiation to the sacrum at 2 years.

PD-1, a follicular T-cell marker useful for recognizing nodular lymphocyte-predominant Hodgkin lymphoma

The nodularity and presence of T-cell rosettes surrounding the neoplastic cells has been described as a defining feature of nodular lymphocyte-predominant Hodgkin lymphoma (NLPHL). We have explored the potential diagnostic value of a new marker (NAT105) that recognizes the antigen PD-1 in a series of 152 cases diagnosed as nodular sclerosis Hodgkin lymphoma, mixed cellularity Hodgkin lymphoma, lymphocyte-rich classic Hodgkin lymphoma, NLPHL, and T-cell/histiocyte-rich B-cell lymphoma (T/HRBCL). All the cases were immunostained with a panel of antibodies against CD10, bcl-6, CXCL13, CD57, and PD-1 (NAT-105). The series includes a set of cases diagnosed as NLPHL with diffuse areas, and a group of borderline cases with features between those of NLPHL and T/HRBCL. Results show that PD-1 (NAT-105) is an excellent immunomarker not only of follicular T-cell rosettes in NLPHL, but also of a subset of lymphocyte-rich classic Hodgkin lymphomas. However, it is not a unique and defining feature of NLPHL. The presence of PD-1-positive (NAT-105) T-cell rosettes seems to be an additional useful feature in the differential diagnosis of NLPHL and T/HRBCL, which is normally a controversial and difficult task. The standard T/HRBCL cases lack follicular T-cell rosettes, whereas most of the borderline cases between the 2 entities have follicular T-cell rosettes, thus suggesting a closer relation with NLPHL.

The Germinal centre-derived lymphomas seen through their cellular microenvironment

The human lymph node is a complex tissue resulting from the microenvironmental organisation of different cell populations linked by topographical and/or functional relationships. Germinal centres (GCs) of lymphoid follicles contain a meshwork of follicular dendritic cells in addition to B-cells and some CD4(+) T cells. Moreover, there is a sharp demarcation around the whole follicle centre, which is highlighted by fibroblastic reticulum cells. On the whole, GC exerts a role in B cell physiology and malignancy. In GC-derived lymphomas, gene expression profiling studies have raised the possibility that survival of the affected patients may be associated with signatures preferentially expressed in non-malignant T cells and macrophages and/or dendritic cells. Immunohistological analyses in lymphoma biopsy samples have confirmed that the biological behaviour and tumour progression may be influenced by the tumour microenvironment. This review will examine GC-derived lymphomas, including follicular lymphomas, Hodgkin lymphomas and angioimmunoblastic T-cell lymphoma, through their integrated cellular microenvironment, highlighting those findings which may serve as a useful surrogate marker for tumour diagnosis or tumour progression, together with key molecules involved in tumour development.

BCL6 gene mutations in transitional cell carcinomas

The B-cell lymphoma-6 (BCL6) gene was initially identified at a translocation site observed frequently in diffuse large B-cell lymphomas. In the present study, BCL6 mutations at the 5' non-coding region in 47 cases of transitional call carcinoma (TCC) were analysed using polymerase chain reaction-single-strand conformation polymorphism. The results were compared with data obtained previously by immunohistochemical staining for the BCL6 protein. Overall, BCL6 mutations were observed in 44.7% of cases. Mutation of the 5' non-coding region was not correlated with histological grade of the tumour; however, the better the histological grade, the greater the mutation rate of the E1.12 fragment. The BCL6 mutation occurred independently of over-expression of the protein. The BCL6 gene mutation and the protein expression were detectable in a large proportion of TCCs. BCL6 protein over-expression as well as BCL6 gene mutation of the E1.12 fragment may play an important role in the morphological differentiation of TCC.

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.

[Classical Hodgkin's lymphoma: biology and grey zones]

Advances in the biology of Hodgkin's lymphoma have lead to the distinction between two entities, "classical" Hodgkin's lymphoma and nodular lymphocyte predominance Hodgkin's lymphoma, previously called nodular paragranuloma, which share distinct clinical aspects. The definition of diagnostic criteria has also been helpful to separate Hodgkin's lymphoma from other lymphomas which can mimick Hodgkin's disease such as anaplastic large cell lymphomas, T-cell/histiocyte rich diffuse large B-cell lymphoma, and some peripheral T-cell lymphomas, mainly angioimmunoblastic-type. Reed-Sternberg cell, the neoplastic cell of "classical" Hodgkin's lymphoma, still retains some secrets. Despite some controversies, there is more and more evidence for a lymphoid B cell origin. The involvement of Epstein-Barr virus, cytokines and/or oncogenes expression in the pathogeny can be suggested, although the precise mechanisms leading to transformation and/or accounting for tumour progression are still elusive. Recently, the roles of the pathway implicating the activation of NFkappaB as well as the autocrine secretion of interleukin-13 have been demonstrated.

The activation profile of tumour-associated reactive T-cells differs in the nodular and diffuse patterns of lymphocyte predominant Hodgkin's disease

AIMS

To compare the activation profile of T-cells in reactive lymphoid follicles with that of tumour-associated T-cells in lymphocyte predominant Hodgkin's disease (LPHD) with a nodular pattern (n = 21), LPHD with partial diffuse growth pattern (n = 11) and T-cell-rich large B-cell lymphoma (TCRLBCL, n = 8).

METHODS AND RESULTS

Reactive germinal centres showed sparse numbers of T-cells positive for CD134, a transient/early T-cell activation marker, and only scattered T-cells in the interfollicular areas positive for CD38, a marker of persistent activation. Lymphoid follicles showing progressive transformation of germinal centres (PTGC) had more numerous CD134+ T-cells which were negative for CD38. Tumour-associated T-cells in nodular LPHD were frequently positive for CD134 (15 of 16 cases, 94%), but negative or only focally positive for CD38 (three of 21 cases, 14%). LPHD with diffuse areas, however, showed increased CD38+ T-cells in the diffuse component in 10 of 11 (90%) cases, with CD134+ T-cells being more prominent in the nodular tumour component. TCRLBCL showed strong, uniform CD38 expression in T-cells and histiocytes in eight cases.

CONCLUSIONS

T-cells in nodular LPHD express markers of transient/early T-cell activation. By contrast, T-cells in the diffuse form of LPHD, similar to those in TCRLBCL, have an immunostaining profile consistent with persistent cellular activation. T-cell activation may precede or accompany histological progression in nodular LPHD and immunostaining for these markers, in small samples or in difficult cases, may be useful in highlighting those cases of LPHD undergoing histological progression.

La maladie de Hodgkin nodulaire à prédominance lymphocytaire et ses diagnostics différentiels

Nodular lymphocyte predominance Hodgkin's disease (NLPHD), previously called nodular paragranuloma, is a rare entity recognized as a clinico-pathological entity distinct from classic Hodgkin's lymphoma. It is an indolent B cell lymphoma derived from a germinal center cell. NLPHD may closely resemble lymphocyte-rich classic Hodgkin's disease (LR-CHD) or T-cell or histiocyte-rich large B-cell lymphoma (TCRLBCL). A reproducible distinction between these entities is difficult but the classification is prognostically relevant. NLPHD is characterized by neoplastic "popcorn" cells CD20+ CD30- CD15- EMA+ Bcl6+ scattered within a nodular background predominantly composed of small B lymphocytes. LR-CHD neoplastic proliferation is composed of CD20+/- CD30+ CD15+/- EMA- Bcl6+/- Reed Sternberg or Hodgkin's cells, scattered within numerous CD3+ T cells. TCRLBCL is an agressive lymphoma composed of CD20+ CD30- CD15- EMA+/- Bcl6+/- polymorphic neoplastic cells, scattered within a mixture of CD3+ T cells and histiocytes. Epstein Barr virus is detectable within half cases of LR-CHD, but never in NLPHD and rarely in TCRLBCL. The transcription factors BOB1, PU-1, BSAP and IRF4 are new markers that could be useful for differential diagnosis.

Nodular lymphocyte-predominant Hodgkin lymphoma with nodules resembling T-cell/histiocyte-rich B-cell lymphoma: differential diagnosis between nodular lymphocyte-predominant Hodgkin lymphoma and T-cell/histiocyte-rich B-cell lymphoma

Nodular lymphocyte-predominant Hodgkin lymphoma (NLPHL) and T-cell/histiocyte-rich B-cell lymphoma (T/HRBCL) are distinct tumors and are treated differently. They are linked by a morphologic and probably a biologic continuum, which renders the differential diagnosis difficult. To develop criteria to distinguish the entities along the morphologic continuum, we correlated the lymph node architecture and immunophenotype of both tumor cells and reactive components of 235 neoplasms in the spectrum of NLPHL and T/HRBCL with clinical data. Two hundred and eighteen cases fitted the World Health Organization (WHO) criteria of NLPHL (139) or T/HRBCL (79). While tumor cells in both entities were immunophenotypically similar, background composition differed: in NLPHL small B cells and CD3+CD4+CD57+ T cells were common, whereas in T/HRBCL, CD8+ cytotoxic T cells and histiocytes dominated. Follicular dendritic cells (FDCs) formed expanded meshworks in NLPHL, whereas they were absent in T/HRBCL. Seventeen cases represented a gray zone: within FDC meshworks, neoplastic B cells resided in a background depleted of small B cells but rich in T cells and histiocytes. Tumor cells either were loosely scattered or formed clusters, thus resembling areas of either T/HRBCL or inflammatory diffuse large BCL (DLBCL) within the nodules. Patients with these NLPHLs with T-cell/histiocyte-rich nodules presented at a high stage and with B symptoms, as in T/HRBCL, but had an excellent survival, as in NLPHL. This morphologic pattern suggests a biologic continuum between NLPHL and T/HRBCL.

Follicular lymphoma without t(14;18) and with BCL-6 rearrangement: a lymphoma subtype with distinct pathological, molecular and clinical characteristics

Translocations involving the BCL-6 gene are frequently observed in diffuse large B cell lymphoma, but have rarely been reported in follicular lymphoma (FL). We studied a distinct cohort of FLs with a 3q27/BCL-6 gene rearrangement, but lacking the t(14;18) translocation. In 13/15 cases, translocations involved the 3q27 and the 14q32 regions. All cases displayed a marked follicular growth pattern and, in some instances, a monocytoid component. Tumor cells were CD5(-) CD20(+) CD23(-) CD43(-) BCL-6(+), and in the main CD10 negative (n = 10, 71%) and BCL-2 negative (n = 11, 78%). When compared to 20 typical t(14;18)(+) FLs, the presence of large follicles (P = 0.01) and a CD10(-)/BCL-2(-) phenotype were more frequently observed (P = 0.001) in our cohort. Clonal mutations arising in the BCL-6 first intron were observed in 5/7 cases with evidence of intraclonal heterogeneity, consistent with a germinal center origin. No significant difference was found in comparison to t(14;18)(+) FL regarding age, sex, performance status, bone marrow involvement or overall survival. However, in the 3q27(+) FL group, a stage III/IV disease and a bulky mass were less frequently observed. This study indicates that 3q27(+) FL without t(14;18) translocation have peculiar clinico-pathologic features and may correspond to a rare and distinct subtype of lymphoma originating from the germinal center.

Progressive transformation of germinal centers: review of histopathologic and clinical features

BACKGROUND

Although progressive transformation of germinal centers (PTGC) in lymph nodes was defined as an entity almost three decade ago, it is not well known to surgical and head and neck pathologists. PTGC may be mistaken for focal nodular lymphocyte predominant Hodgkin's Disease (NLPHD).

OBJECTIVE

To review the histopathologic and clinical features of PTGC, and PTGC's relationship with lymphoid neoplasia in pediatric and adult populations. HISTOPATHOLOGIC FEATURES: PTGC occurs in 10-15% of enlarged lymph nodes with reactive follicular hyperplasia. PTGC is characterized as a nodule, which is three to five times the size of a typical reactive follicle, with mantle zone small B-cells infiltrating the residual germinal center. Epithelioid histiocytic clusters, immunoblasts, mononuclear cells, and eosinophils may also be present. Solitary or multiple nodules may be found. The immunophenotypes of both PTGC and NLPHD may be identical (CD45+, CD20+, CD15-, CD30-). The nodules in PTGC are relatively well defined, with those in NLPHD being more irregular.

CLINICAL FEATURES

PTGC occurs in children (20%, mean age 11 years) and adults (80%, mean age 28 years), with a male predominance (3:1). PTGC is associated with Hodgkin's disease (HD) in 30-35% of patients. PTGC may precede, follow, or be concurrent with HD. Recurrent PTGC is more common in children (50 vs. 23%). Cervical lymph nodes account for almost 50% of cases, with oral cavity involvement also reported.

CONCLUSION

PTGC occurs frequently in lymph nodes with reactive follicular hyperplasia, may resemble focal NLPHD, and has a nebulous association with NLPHD. PTGC is not considered a premalignant condition.

Progressive transformation of germinal centers. Report of 2 cases and review of the literature

Progressive transformation of germinal centers (PTGC) is a disease of mostly young adults that presents as unexplained, asymptomatic, localized or generalized lymphadenopathy which is usually persistent or recurrent over periods of many years. Histologically, the germinal centers contain a variable proportion of small mantle zone lymphocytes and thus become progressively transformed and may result in the loss of clear demarcation between them and the mantle zone. Here, we describe two cases of this disease and review the literature on the association of PTGC with lymphocyte-predominant Hodgkin's disease.

T-cell/histiocyte-rich large B-cell lymphoma is a disseminated aggressive neoplasm: differential diagnosis from Hodgkin's lymphoma

AIMS

An accurate diagnosis of T-cell/histiocyte-rich large B-cell lymphoma needs to take into consideration those forms of Hodgkin's lymphoma also characterized by a predominance of small lymphocytes and histiocytes, i.e. nodular lymphocyte predominance Hodgkin's lymphoma and lymphocyte-rich classical Hodgkin's lymphoma. We have studied the clinical, phenotypic and genetic features of a series of 12 cases of T-cell/histiocyte-rich large B-cell lymphoma along with 18 cases of Hodgkin's lymphoma for comparative purposes.

METHODS AND RESULTS

Of the Hodgkin's lymphoma cases, there were 11 lymphocyte predominance type and seven classic type. T-cell/histiocyte-rich large B-cell lymphomas presented usually in advanced stages (III or IV in 11/12 cases), frequently with 'B' symptoms (6/9 cases), and followed a more aggressive course than Hodgkin's lymphoma (4/8 patients died due to the tumour in T-cell/histiocyte-rich large B-cell lymphoma versus 0/15 in Hodgkin's lymphoma). T-cell/histiocyte-rich large B-cell lymphoma cases showed diffuse effacement of the nodal architecture by a proliferation of scattered large atypical B-cells obscured by a background of small T-lymphocytes (more CD8+, TIA1+ than CD57+). Five cases showed also a prominent histiocytic component. The large B-cells expressed CD45 and often EMA (6/10 cases). On the other hand, CD 30, CD15 and latent infection by Epstein-Barr virus (EBV) were generally lacking. bc l6 and CD10 were, respectively, detected in 6/6 and 1/5 cases. Conventional polymerase chain reaction (PCR) showed monoclonal immunoglobulin heavy chain (IgH) gene rearrangements in all T-cell/histiocyte-rich large B-cell lymphomas studied (5/5), but did not detect any case with t(14;18) involving the major breakpoint region (0/4).

CONCLUSIONS

The differential diagnosis of T-cell/histiocyte-rich large B-cell lymphoma from Hodgkin's lymphoma is facilitated by the integration of different immunophenotypic, molecular and clinical findings. T-cell/histiocyte-rich large B-cell lymphoma is a monoclonal neoplasm of bc l6+ B-cells with a phenotypic profile similar to lymphocyte predominance Hodgkin's lymphoma, suggesting a germinal centre origin and a possible relation to this disease. Therefore, in order to distinguish it from lymphocyte predominance Hodgkin's lymphoma, characterization of the reactive background, IgH gene rearrangement studies by conventional PCR and clinical features are more useful. In contrast, T-cell/histiocyte-rich large B-cell lymphoma can be distinguished from classical Hodgkin's lymphoma thanks to the presence of monoclonal IgH rearrangement and the CD 30-CD15-CD45+EMA+ immunophenotypic profile of the neoplastic cells in T-cell/histiocyte-rich large B-cell lymphoma.

T-cell-rich B-cell lymphoma - diagnostic and therapeutic aspects

BACKGROUND

Morphologically, T-cell-rich B-cell lymphoma (TCRB-NHL) may be indistinguishable from Hodgkin's disease (HD). Immunophenotyping may be helpful in the separation of these entities. TCRB-NHL is occasionally misdiagnosed and treated as HD. However, information is limited regarding clinical characteristics and outcome of this patient population. Furthermore, knowledge concerning any association with Epstein-Barr virus (EBV) in TCRB-NHL, as well as the immunophenotype of reactive T-cells and the expression of T-cell intracellular antigen-1 (TIA-1), granzyme B (GrB) and the CD3-zeta-chain is limited.

PATIENTS AND METHODS

We have re-evaluated 251 tumour biopsies from patients aged > or =15 years with HD diagnosed 1985-1994. Reclassification from HD to TCRB-NHL was done in 12 cases (5%). Six TCRB-NHL patients initially diagnosed and treated as B-NHL were also included. All TCRB-NHL biopsies were analysed for latent membrane protein 1 (LMP-1), CD4, CD8, CD56, CD57, TIA-1, GrB and CD3-zeta-chain.

RESULTS

Twelve cases of TCRB-NHL were initially subclassified as HD (lymphocyte predominance 5, nodular sclerosis 3, and mixed cellularity 4). Of these 12 TCRB-NHL patients, 6 were given radiotherapy alone, 5 MOPP/ABVD or similar combination chemotherapy, and one patient combined modality treatment. Male sex (p<0.05) and inguinal involvement (p<0.001) were significantly more frequent when TCRB-NHL patients receiving HD treatment (n=12) were compared with the remaining patients with confirmed (conf) HD, while no significant differences were seen with regard to stage, bone marrow infiltration, splenomegaly or cause-specific survival. Similar results were achieved when all TCRB-NHL patients (n=18) were compared to conf HD patients. Lymphoma cells in three samples stained positively for LMP-1. A decreased expression of CD3-zeta-chain was seen in 9/14 tumour biopsies.

CONCLUSION

Immunohistochemistry makes it possible to identify cases of TCRB-NHL that are morphologically difficult to distinguish from HD. The outcome of TCRB-NHL patients treated as having HD was comparable with that of the remaining HD population.

Dismantling the germinal center: comparing the processes of transformation, regression, and fragmentation of the lymphoid follicle

The pathologic and immunologic features of the formation of the germinal center have been extensively studied. The process of dissolution of the germinal center is not as well understood. Different patterns of germinal-center breakdown are commonly encountered in diagnostic lymph node biopsy specimens and frequently present difficulties in diagnosis. The current immunologic understanding of germinal-center dynamics is reviewed and correlated with the histologic and immunophenotypic features of three broad classes of germinal center dissolution, namely progressive transformation, regression, and follicle fragmentation. The author suggests that these different patterns represent alternate responses to antigenic stimulation. The relationships of progressive transformation to Hodgkin's disease and of follicular regression to Castleman's disease are discussed.

Hodgkin's lymphoma: the pathologist's viewpoint

Despite its well known histological and clinical features, Hodgkin's lymphoma (HL) has recently been the object of intense research activity, leading to a better understanding of its phenotype, molecular characteristics, histogenesis, and possible mechanisms of lymphomagenesis. There is complete consensus on the B cell derivation of the tumour in most cases, and on the relevance of Epstein-Barr virus infection and defective cytokinesis in at least a proportion of patients. The REAL/WHO classification recognises a basic distinction between lymphocyte predominance HL (LP-HL) and classic HL (CHL), reflecting the differences in clinical presentation and behaviour, morphology, phenotype, and molecular features. CHL has been classified into four subtypes: lymphocyte rich, nodular sclerosing, with mixed cellularity, and lymphocyte depleted. The borders between CHL and anaplastic large cell lymphoma have become sharper, whereas those between LP-HL and T cell rich B cell lymphoma remain ill defined. Treatments adjusted to the pathobiological characteristics of the tumour in at risk patients have been proposed and are on the way to being applied.

Proteins encoded by genes involved in chromosomal alterations in lymphoma and leukemia: clinical value of their detection by immunocytochemistry

Acquired chromosomal anomalies (most commonly translocations) in lymphoma and leukemia usually result in either activation of a quiescent gene (by means of immunoglobulin or T-cell-receptor promotors) and expression of an intact protein product, or creation of a fusion gene encoding a chimeric protein. This review summarizes current immunocytochemical studies of these 2 categories of oncogenic protein, with emphasis on the clinical relevance of their detection in diagnostic samples. Among the quiescent genes activated by rearrangement, expression of cyclin D1 (due to rearrangement of the CCND1 [BCL-1] gene) is a near-specific marker of t(11;14) in mantle cell lymphoma; BCL-2 expression distinguishes follicular lymphoma cells from their nonneoplastic counterparts in reactive germinal centers and appears to be an independent prognostic marker in diffuse large cell lymphoma; and TAL-1 (SCL) expression identifies T-cell acute lymphoblastic neoplasms in which this gene is activated. The protein products of other genes activated by chromosomal rearrangement have a role as markers of either lineage (eg, PAX-5 [B-cell-specific activator protein] for B cells, including B-lymphoblastic neoplasms), or maturation stage (eg, BCL-6 for germinal-center and activated B cells and MUM-1/IRF4 for plasma cells). Currently, no hybrid protein encoded by fusion genes is reliably detectable by antibodies recognizing unique junctional epitopes (ie, epitopes absent from the wild-type constituent proteins). Nevertheless, staining for promyelocytic leukemia (PML) protein will detect acute PML with t(15;17) because the microspeckled nuclear labeling pattern for PML-RARalpha is highly distinctive. Similarly, antibodies to the anaplastic lymphoma kinase (ALK) tyrosine kinase are valuable (because wild-type ALK is not found in normal lymphoid tissue) in detecting neoplasms (CD30-positive large T-cell lymphomas) with t(2;5) or its variants. Thus, immunocytochemical detection of the products of many rearranged genes in lymphoma and leukemia can be clinically informative and provide information on cellular and subcellular protein expression that cannot be inferred from studies based on messenger RNA.

Alterations on the 5' noncoding region of the BCL-6 gene are not correlated with BCL-6 protein expression in T cell non-Hodgkin lymphomas

The BCL-6 proto-oncogene is expressed in germinal center B lymphocytes, in their neoplastic counterparts, and in a subpopulation of germinal center and perifollicular T lymphocytes. Rearrangements and/or mutations of the 5' noncoding region of the bcl-6 gene have been demonstrated in a large majority of diffuse large B cell lymphomas. Some, but not all, of these genetic alterations lead to dysregulation of the protein. Recently, anaplastic large cell lymphomas with T and null cell phenotypes, as well as T lymphoblastic lymphomas, have also been reported to exhibit immunoreactivity to the anti-BCL-6 antibody. We collected 33 T cell non-Hodgkin lymphomas (T-NHLs) and analyzed their expression of the BCL-6 protein by immunohistochemistry and investigated the organization of the bcl-6 gene by Southern blot and single strand conformation polymorphism (SSCP). The expression of BCL-6 was demonstrated in 37.5% of lymphoblastic (LBL), 40% of anaplastic large cell (ALCL), and 33% of peripheral T cell lymphomas (PTCL). BCL-6-positive malignant cells exhibited the CD4+ or CD4+/CD8+ phenotype. The bcl-6 gene was in a germline configuration in all T-NHLs examined, and a mutation at the first exon-intron boundary region structure of the wild-type bcl-6 gene was detected in 3 of 12 PTCL. One case of PTCL with mutations of the 5' noncoding region expressed BCL-6. In conclusion, expression of the BCL-6 protein is demonstrable independently of bcl-6 alterations in T-NHLs. This further suggests that molecular mechanisms other than rearrangements and/or mutations of the 5' noncoding region of the bcl-6 gene can result in expression of the protein. Whether these lymphomas arose from T cells expressing BCL-6 or expressed BCL-6 as part of the malignant transformation process needs to be determined. Finally, structural alterations of bcl-6 are rare in T-NHLs, but mutations do occur in the 5' noncoding region. We suggest that expression of BCL-6 in T cells may facilitate lymphomagenesis by repressing critical cytokines and cell cycle regulators.