Demonstration of light chain mRNA in Hodgkin's disease

Ultrasensitive RNA In Situ Hybridization for Kappa and Lambda Light Chains Assists in the Differential Diagnosis of Nodular Lymphocyte-predominant Hodgkin Lymphoma

Establishing a diagnosis of nodular lymphocyte-predominant Hodgkin lymphoma (nLPHL) is often challenging as the differential diagnosis is broad, including classic Hodgkin lymphoma (cHL), progressive transformation of germinal centers (PTGC), and other lymphoproliferative disorders. In this study, we investigate the utility of a recently described ultrasensitive in situ hybridization assay for kappa and lambda immunoglobulin light chains in distinguishing nLPHL, cHL, and PTGC. A total of 72 cases were examined (21 nLPHL, 33 cHL, and 18 PTGC). In nLPHL, the large neoplastic cells were light chain restricted in 21/21 (100%) cases (16 kappa, 5 lambda). In contrast, Reed-Sternberg cells of cHL were negative for kappa and lambda in all cases (0/33, 0%; P <0.001). In PTGC, polytypic B cells were noted in mantle zones and germinal centers in all cases, with 1 case (5%) also showing focal collections of light chain restricted large B cells. Background monotypic small B cells were identified in 3 cases, including 1 nLPHL and 2 cHL (1 of which arose in chronic lymphocytic leukemia). Ultrasensitive in situ hybridization for kappa and lambda is a useful addition to a standard immunophenotyping panel for the evaluation of suspected nLPHL.

Expression pattern of intracellular leukocyte-associated proteins in primary mediastinal B cell lymphoma

Two microarray studies of mediastinal B cell lymphoma have shown that this disease has a distinct gene expression profile, and also that this is closest to the pattern seen in classical Hodgkin's disease. We reported previously an immunohistologic study in which the loss of intracellular B cell-associated signaling molecules in Reed-Sternberg cells was demonstrated, and in this study we have investigated the expression of the same components in more than 60 mediastinal B cell lymphomas. We report that these signaling molecules are frequently present, and in particular that Syk, BLNK and PLC-gamma2 (absent from Reed-Sternberg cells) are present in the majority of mediastinal B cell lymphomas. The overall pattern of B cell signaling molecules in this disease is therefore closer to that of diffuse large B cell lymphoma than to Hodgkin's disease, and is consistent with a common cell of origin as an explanation of the similar gene expression profiles.

Epigenetic silencing of the immunoglobulin heavy-chain gene in classical Hodgkin lymphoma-derived cell lines contributes to the loss of immunoglobulin expression

Immunoglobulin production is impaired in Hodgkin and Reed-Sternberg (HRS) cells of classical Hodgkin lymphoma (cHL) in spite of functional clonal rearrangements. The presence of "crippling" mutations in coding and regulatory regions, as well as down-regulation of B-cell-specific transcription factors, has been suggested as a potential reason for the lack of immunoglobulin (Ig) chain gene transcription. We have investigated the impact of epigenetic silencing in suppressing Ig heavy (H)-chain expression. Chromatin immunoprecipitation (ChIP) was used to analyze transcription factor binding to octamer motifs present in the IgH regulatory regions. Transcription factors were bound to these motifs in control cell lines, however, they were absent in the cHL-derived cell lines KMH2, L1236, and L428. Ectopic expression of octamer-binding transcription factor (Oct2) and/or B-cell Oct binding protein/Oct-binding factor (BOB.1/OBF.1) did not result in any measurable binding to these sites. Increased histone 3 Lysine 9 (H3-K9) methylation was observed in the promoter region of the IgH locus in L428 and L1236 cells. This is a typical feature of heterochromatic, transcriptionally silent regions. Treatment of cHL-derived cell lines with the DNA demethylating agent 5-aza-2'-deoxycytidine (5-aza-dC) partially reactivated IgH transcription and affected chromatin modifications. Our results suggest an important role of epigenetic silencing in the inhibition of IgH transcription in HRS cells.

Biology of Hodgkin's lymphoma

Significant progress has been made in recent years in our understanding of the cellular origin of Hodgkin and Reed-Sternberg (HRS) cells in Hodgkin's lymphoma (HL). It is now clear that in most instances HRS cells represent clonal populations of transformed germinal centre (GC) B cells. While the tumour cells in the lymphocyte predominant type of the disease resemble mutating and antigen-selected GC B cells, there is evidence that HRS cells in classical HL originate from pre-apoptotic GC B cells. HRS cells of the recently defined novel subtype lymphocyte-rich classical HL moleculary resemble HRS cells of the other types of classical HL, but there appear to be phenotypic differences. In rare cases, HRS cells derive from T cells. In contrast to previous speculations, cell fusion apparently does not play a role in the generation of the tumour clone. By gene expression profiling of HL cell lines, it became evident that HRS cells have lost most of the B cell-typical gene expression program, which may explain why these cells can persist without B cell receptor expression and which suggests that at least one of the transforming events involved in HL pathogenesis affects a master regulator of cell lineage identity.

Molecular biology of Hodgkin's lymphoma

Hodgkin's lymphoma (HL) is characterized by typical mononucleated Hodgkin and multinucleated Reed-Sternberg cells, which occur at low frequency in a mixed cellular infiltrate in the tumor tissue. Because of the rarity of these cells and their unusual immunophenotype, which is strikingly different from those of all normal hematopoietic cell types, the origin of these cells and their clonality have long been unclear. Single-cell studies of rearranged immunoglobulin genes showed that Hodgkin and Reed-Sternberg (HRS) cells represent clonal tumor-cell populations derived from germinal center B cells. In classical HL, the detection of obviously crippling immunoglobulin gene mutations in a fraction of the cases suggests that HRS cells may derive from germinal center B cells that have lost the capacity to be positively selected by antigen and that normally would have undergone apoptosis. In rare cases, HRS cells represent transformed T lymphocytes. The transforming events involved in malignant transformation of HRS cells are still largely unknown. Constitutive activation of the transcription factor NFkappaB, which can, for example, be induced through Epstein-Barr virus transformation of HRS cells or destructive somatic mutations of the inhibitor of NFkappaB, is likely to be a key event in HL pathogenesis. Significant progress has been made in our understanding of the cellular interactions in HL tissues, which are mainly mediated by a large variety of cytokines and chemokines.

Defective octamer-dependent transcription is responsible for silenced immunoglobulin transcription in Reed-Sternberg cells

The absence of immunoglobulin (Ig) expression in B-cell-derived Hodgkin and Reed-Sternberg (HRS) cells of classical Hodgkin disease (cHD) was initially suggested to be caused by crippling mutations in the Ig promoter or coding region. More recent investigations have, however, challenged this concept. This study addressed the role of mutations in the Ig promoter region in HRS cells. Nine cases of cHD and 3 B-cell-derived HD lines were analyzed for mutations in the TATA box and octamer motif of the Ig promoter. Mutations in the octamer motif were found in only 1 of the 9 cases and in 1 of the 3 HD cell lines (L1236). Furthermore, in all cases either a complete lack or strong reduction in the expression of the Oct2 transcription factor and the BOB.1/OBF.1 coactivator were found. The relevance of the rare promoter mutations was investigated by assaying the activity of Ig promoter reporter constructs transfected into the HD cell line L1236, which harbors a mutated octamer motif. These Ig reporter constructs were completely inactive in L1236 cells; however, their activity could be reconstituted by the cotransfection of a BOB.1/OBF.1 expression vector. The additional transfection with an Oct2 expression vector did not further enhance the Ig promoter activity. The conclusions drawn from these results are that crippling mutations in the Ig promoter and coding region are not the sole cause for the lack of Ig expression in HRS cells and that defects in the transcription machinery such as absence of BOB.1/OBF.1 are more important for this phenomenon.

Down-regulation of BOB.1/OBF.1 and Oct2 in classical Hodgkin disease but not in lymphocyte predominant Hodgkin disease correlates with immunoglobulin transcription

In contrast to the tumor cells (L&H cells) of lymphocyte predominant Hodgkin disease (LPHD), Hodgkin and Reed-Sternberg (HRS) cells of classical Hodgkin disease (cHD) are unable to transcribe immunoglobulin, despite the presence of rearranged immunoglobulin genes. Although initial studies have suggested crippling immunoglobulin gene mutations to be the cause of absent immunoglobulin expression in cHD, recent work of our group has demonstrated an impaired activation of the immunoglobulin promoter as a superior mechanism. As immunoglobulin transcription is mainly regulated by the B-cell transcription factors Oct2 and BOB.1/OBF.1, we analyzed 35 cases of LPHD, 32 cases of cHD, and 2 Hodgkin disease cell lines for the expression of these transcription factors and also in parallel for immunoglobulin expression. Our results demonstrate an absence of Oct2 and/or BOB.1/OBF.1 in cHD and a striking overexpression of Oct2 in LPHD. Immunoglobulin expression was lacking in cHD but present in LPHD. Furthermore, the reintroduction of BOB.1/OBF.1 and Oct2 into cultured HRS cells restored the activity of cotransduced immunoglobulin promoter constructs. Our findings dismiss the concept that the different immunoglobulin expression in cHD and LPHD is due to disrupting mutations of immunoglobulin V genes in cHD but is most likely due to a down-regulation of Oct2 and/or BOB.1/OBF.1. This study further revealed Oct2 as a new and valuable marker for the identification of L&H cells and their distinction from HRS cells. The impairment of immunoglobulin transcription with a down-regulated synthesis of Oct2 and BOB.1/OBF.1 is the first established general recurrent defect found in HRS cells.

Hodgkin and Reed-Sternberg cells represent an expansion of a single clone originating from a germinal center B-cell with functional immunoglobulin gene rearrangements but defective immunoglobulin transcription

Single cell studies aimed at clarifying the nature and clonality of Hodgkin and Reed-Sternberg (HRS) cells of classical Hodgkin's disease (HD) have so far produced conflicting results. Using an improved single cell procedure, the HRS cells of 25 patients with nodular sclerosing HD lacking B- and T-cell antigens, with and without Epstein-Barr virus infection, were analyzed for the presence of immunoglobulin (Ig) gene rearrangements. One patient with HD developed follicular lymphoma 2 years later. Both lymphomas originated from a common precursor identified as a germinal center B cell. The data show that all but one of the investigated cases harbored rearranged Ig genes, which were clonal in all instances and carried a high load of somatic mutations. The Ig coding capacity was preserved in 18 of the 24 cases (75%) with rearrangements. However, expression of Ig messenger RNA was not detectable in the HRS cells with the exception of Ig kappa light chain expression in some tumor cells of 1 case. The lack of Ig gene transcription in HRS cells was confirmed by analyzing the HD cell lines L428 and KM-H2 in transient transfection experiments. An Ig promoter/enhancer reporter construct showed virtually no activity in these cells compared to 5 control B-cell lines. We conclude that (1) classical HD is a B-cell lymphoma in most instances, (2) HRS cells are clonal without any exception, (3) they are derived from germinal center B-cells that (4) mostly lack crippling mutations but (5) have consistently lost their Ig gene transcription ability, due to functional defects in the Ig gene regulatory elements.

Somatic Mutations Within the Untranslated Regions of Rearranged Ig Genes in a Case of Classical Hodgkin’s Disease as a Potential Cause for the Absence of Ig in the Lymphoma Cells

Hodgkin–Reed-Sternberg (H-RS) cells are clonal B cells carrying Ig gene rearrangements. However, in situ hybridization methods failed to demonstrate Ig gene expression in H-RS cells of classical Hodgkin’s disease (HD). Because somatic mutations rendering potentially functional Ig gene rearrangements nonfunctional were detected in some cases of the disease, it was speculated that H-RS cells in classical HD may have lost the ability to express antigen receptor as a rule. Recently, we established a novel cell line (L1236) from H-RS cells of a patient with mixed cellularity subtype of HD. L1236 cells harbor a potentially functional VH1 and a potentially functional Vκ3 gene rearrangement. However, no antibody expression was detected. To show potential reasons for this lack of Ig expression, we analyzed the genomic organization of the Ig genes and their transcription in the primary and cultivated H-RS cells of this patient. The H-RS cells were found to have switched their isotype to IgG4, confirming their mature B-cell nature. By amplifying cDNA from L1236 cells as well as from frozen biopsy material transcripts of the Vκ3 and the VH1 gene rearrangement were detected for both sources of cDNA. However, Northern blot hybridization of L1236 RNA failed to demonstrate VH1 and Vκ3 transcripts, indicating only a low level of transcription. Sequence analysis of the promoter and leader regions of the VH1 gene rearrangement from L1236 cells as well as from lymphoma-affected tissue showed a somatic mutation in the conserved octamer motif of the promoter region. Somatic mutations were also detected within the 3′ splice site of the leader intron and adjacent nucleotides in the rearranged Vκ light chain gene, leading to aberrant splicing. These mutations might prevent the generation of adequate amounts of functional Ig gene transcripts as template for translation into protein. Thus, mutations in H-RS cells that prevent Ig gene expression might also be located outside the coding region of the Ig genes.

Somatic Mutations Within the Untranslated Regions of Rearranged Ig Genes in a Case of Classical Hodgkin’s Disease as a Potential Cause for the Absence of Ig in the Lymphoma Cells

Hodgkin–Reed-Sternberg (H-RS) cells are clonal B cells carrying Ig gene rearrangements. However, in situ hybridization methods failed to demonstrate Ig gene expression in H-RS cells of classical Hodgkin’s disease (HD). Because somatic mutations rendering potentially functional Ig gene rearrangements nonfunctional were detected in some cases of the disease, it was speculated that H-RS cells in classical HD may have lost the ability to express antigen receptor as a rule. Recently, we established a novel cell line (L1236) from H-RS cells of a patient with mixed cellularity subtype of HD. L1236 cells harbor a potentially functional VH1 and a potentially functional Vκ3 gene rearrangement. However, no antibody expression was detected. To show potential reasons for this lack of Ig expression, we analyzed the genomic organization of the Ig genes and their transcription in the primary and cultivated H-RS cells of this patient. The H-RS cells were found to have switched their isotype to IgG4, confirming their mature B-cell nature. By amplifying cDNA from L1236 cells as well as from frozen biopsy material transcripts of the Vκ3 and the VH1 gene rearrangement were detected for both sources of cDNA. However, Northern blot hybridization of L1236 RNA failed to demonstrate VH1 and Vκ3 transcripts, indicating only a low level of transcription. Sequence analysis of the promoter and leader regions of the VH1 gene rearrangement from L1236 cells as well as from lymphoma-affected tissue showed a somatic mutation in the conserved octamer motif of the promoter region. Somatic mutations were also detected within the 3′ splice site of the leader intron and adjacent nucleotides in the rearranged Vκ light chain gene, leading to aberrant splicing. These mutations might prevent the generation of adequate amounts of functional Ig gene transcripts as template for translation into protein. Thus, mutations in H-RS cells that prevent Ig gene expression might also be located outside the coding region of the Ig genes.

The origin of Hodgkin and Reed/Sternberg cells in Hodgkin's disease

One of the characteristic features of Hodgkin's disease (HD) is the presence of a small population of often bizarre-looking large mono- or multinucleated Hodgkin and Reed-Sternberg (HRS) cells within the affected tissue. Recent cytogenetic investigations, studies of Epstein-Barr virus (EBV) genomes present in HRS cells, and analyses of Ig gene rearrangements amplified from single, micromanipulated HRS cells show that these cells largely represent clonal populations. The finding of Ig gene rearrangements in HRS cells in most cases of HD identifies B cells as the precursors of HRS cells in most if not all cases. Furthermore, the presence and pattern of somatic mutations within the rearranged Ig genes show that HRS cells in classical (i.e. nodular sclerosis, mixed cellularity, and lymphocyte depletion HD) as well as lymphocyte predominant (LP) HD originate from germinal center (GC) B cells. Ongoing somatic mutation and evidence for selection link HRS cells from LP HD to a mutating, antigen-selected GC B cell. In classical HD, the finding of "crippling" mutations and lack of stringent selection for antigen receptor expression suggests that in this case HRS cells are derived from a compartment of GC B cells that were destined to die but escaped apoptosis by some transforming event. One candidate for the latter is EBV infection.

Comparison of in situ hybridisation and polymerase chain reaction in the diagnosis of B cell lymphoma

AIM

To compare the sensitivity of the detection of immunoglobulin light chain messenger RNA (mRNA) restriction by in situ hybridisation (ISH) and clonal immunoglobulin heavy chain gene rearrangements by polymerase chain reaction (PCR) in the diagnosis of B cell lymphoma.

METHODS

Analyses were applied to formalin fixed, paraffin wax embedded, routine diagnostic specimens from cases with a provisional diagnosis of reactive lymph node (n = 23), B cell lymphoma (n = 21), and T cell lymphoma (n = 4). Nonisotopic ISH for kappa and lambda immunoglobulin light chain mRNA was performed using both fluorescein and digoxigenin labelled oligodeoxynucleotide probe cocktails. PCR was carried out on DNA extracted from sections using primers to framework 3 (Fr3) of the V segments and to conserved sequences from the J regions of the immunoglobulin heavy chain genes.

RESULTS

All reactive lymph nodes showed a polyclonal pattern of light chain mRNA by ISH, although one showed an excess of kappa positive cells. Nineteen of 21 (90%) cases of B cell lymphoma showed light chain restriction, and a further case showed a vast excess of kappa positive cells. By PCR, 20 of 23 reactive nodes (87%) showed a polyclonal pattern. In 13 of 21 B cell lymphomas (62%) a clonal band was detected.

CONCLUSION

In the diagnosis of B cell lymphoma in routinely processed diagnostic material ISH for light chain mRNA was more sensitive (90%) than PCR for heavy chain gene rearrangement using Fr3 and J region primers (62%).

Sequential malt lymphomas of the stomach, small intestine, and gall bladder

Low grade lymphomas of mucosa associated lymphoid tissue (MALT) are indolent neoplasms that, although tending to remain localised for many years, may spread to other mucosal sites. A 53 year old woman treated by total gastrectomy for low grade MALT lymphoma of the stomach developed a recurrence in the small bowel 18 years later, and a further recurrence involving the gall bladder after three years in complete clinical remission after chemotherapy. In situ hybridisation showed that the small intestine and gall bladder recurrences had the same pattern of light chain restriction. Tumour from all three sites was shown to be derived from a single clone by the demonstration of an identical immunoglobulin heavy chain gene rearrangement by the polymerase chain reaction. The case illustrates the propensity of MALT lymphomas to "home" to mucosal sites and gives an insight into their behavior over an extended follow up.

A renin secreting ovarian steroid cell tumour associated with secondary polycythaemia

A 67-year-old woman presented with dry skin, facial hair, hoarse voice, and weight gain. She was hypertensive (168/ 96 mm Hg), her haemoglobin concentration was 19 g/l, and haematocrit was 55.7%. The diagnosis of probable secondary polycythaemia was made. Blood testosterone concentration was 44 nmol/l (normal < 5) and was not suppressed by dexamethasone, suggesting a neoplastic source rather than a pituitary abnormality. Transvaginal ultrasound revealed a hypoechoic solid mass in the left ovary suggestive of a solid ovarian tumour. Hysterectomy and bilateral salpingo-oophorectomy were performed following which testosterone concentration returned to normal. Immunocytochemistry provided evidence of renin synthesis. This is a case of an unusual steroid cell tumour that caused virilisation accompanied by symptoms of secondary polycythaemia presumably as a result of erythropoietin production. This is the second case of a steroid cell tumour with an erythropoietic effect and the first that shows evidence of renin synthesis.

Hodgkin and Reed-Sternberg cells in lymphocyte predominant Hodgkin disease represent clonal populations of germinal center-derived tumor B cells

Among the four subtypes of Hodgkin disease (HD), lymphocyte-predominant (LP) HD is now generally considered as a separate entity. The B cell nature of the typical Hodgkin and Reed-Sternberg (HRS) cells and their variants (L and H, lymphocytic and histiocytic cells) in LP HD has long been suspected, but the question of whether these cells represent a true tumor clone is unclear. We previously demonstrated clonal Ig gene rearrangements in one case of LP HD. In the present study, five cases of LP HD were analyzed by micromanipulation of single HRS cells from frozen tissue sections and DNA amplification of rearranged Ig heavy chain genes from those cells. Clonal V gene rearrangements harboring somatic mutations were detected in each case. In three cases ongoing somatic mutation was evident. This shows that HRS cells in LP HD are a clonal tumor population derived from germinal center B cells. The pattern of somatic mutation indicates that HRS cells in LP HD are selected for antibody expression. This, and the presence of ongoing mutation discriminates LP from classical HD.

Clonality in nodular lymphocyte-predominant Hodgkin's disease

BACKGROUND

There is general agreement that lymphocytic and histiocytic (L&H) cells, the variants of Reed-Sternberg cells in nodular lymphocyte-predominant Hodgkin's disease, belong to the B-cell lineage. However, the clonality of L&H cells remains controversial.

METHODS

We used complementarity-determining region 3 (CDR3) of the immunoglobulin heavy-chain gene as a clonal marker to study individual L&H cells isolated by micromanipulation from tissue sections of five patients with nodular lymphocyte-predominant Hodgkin's disease. The heavy-chain CDR3 of each cell was amplified by the polymerase chain reaction. The products were analyzed by gel electrophoresis, and representative amplification products from each patient were sequenced.

RESULTS

L&H cells whose heavy-chain CDR3 was related, indicating the presence of a clonal population, were detected in all five patients and were the dominant population in three. In four of the five patients, members of the clone were found in different nodules in the tissue section, different tissue blocks from the same tumor, or different lymph nodes from the same patient. The CDR3 sequences in each clone frequently contained nucleotide substitutions indicative of intraclonal mutation.

CONCLUSIONS

Clonal populations of L&H cells occur in nodular lymphocyte-predominant Hodgkin's disease. Intraclonal variation in nucleotide sequences suggests that hypermutation of the heavy-chain CDR3 continues to occur among the clonal progeny.

In situ hybridization and its diagnostic applications in pathology

In situ hybridization (ISH) is a technique by which specific nucleotide sequences are identified in cells or tissue sections. These may be endogenous, bacterial or viral, DNA or RNA. On the basis of research applications, the technique is now being translated into diagnostic practice, mainly in the areas of gene expression, infection and interphase cytogenetics. Diagnostic applications are most often based on short nucleotide sequences (oligomers) labelled with non-isotopic reporter molecules, and sites of binding may be localized by histochemical or immunohistochemical methods. The technique can be applied to routinely fixed and processed tissues; with some targets, it is even possible to obtain hybridization in autopsy material. ISH has been used to detect messenger RNA (mRNA) as a marker of gene expression, where levels of protein storage are low; for example, to confirm an endocrine tumour as the source of excess hormone production. Its application in infectious diseases has to date been mainly in viral infections, such as the typing of human papillomavirus (HPV) or the detection of Epstein-Barr virus by the presence of small nuclear RNAs (EBERs). The expression of mRNAs for histone proteins has been used to detect cells in S phase, and related methods may be applied to detect apoptotic cells. Using probes to chromosome-specific sequences, it is possible to detect aneuploidy, and to document changes in specific chromosomes, which may have prognostic significance in some tumours, such as B-cell chronic lymphatic leukaemia. Using sequence-specific probes, translocations can be identified, such as the t(11;12) of Ewing's sarcoma. This review presents an outline of the technique of in situ hybridization and discusses areas of current and potential diagnostic application.

Immunoglobulin light chain mRNA detected by in situ hybridisation in diagnostic fine needle aspiration cytology specimens

AIMS

To demonstrate expression of immunoglobulin light chain mRNA in diagnostic fine needle aspiration (FNA) cytology specimens using an in situ hybridisation (ISH) technique; and to evaluate ISH in a series of reactive lymphoid proliferations and malignant lymphomas.

METHODS

Forty diagnostic FNA specimens showing a lymphoid cell population were examined for immunoglobulin light chain mRNA expression using ISH. Aspirates were obtained from lymph node (n = 34), salivary gland (n = 3), subcutaneous tissue, thyroid and breast (n = 1 each). The cases included 20 B cell lymphomas, five cases of Hodgkin's disease and 15 reactive lymphoid proliferations. Comparison with light chain immunoreactivity was made in 36 cases and histological correlation from biopsy material was available in 24.

RESULTS

Immunoglobulin light chain restriction was demonstrated in 14 of 20 B cell lymphomas using ISH and in six of 17 B cell lymphomas using immunocytochemistry. A polytypic pattern of light chain expression was observed in four of five cases of Hodgkin's disease with both techniques, and in 12 of 15 and 11 of 14 reactive lymphoid proliferations using ISH and immunocytochemistry, respectively.

CONCLUSIONS

The assessment of immunoglobulin light chain expression is a useful adjunct to morphology in the diagnosis of reactive and malignant lymphoid proliferations in FNA specimens. Light chain restriction can be shown using either immunocytochemistry or ISH, but the latter is more sensitive in the diagnosis of B cell lymphoma.

Pathophysiology of Hodgkin's disease: functional and molecular aspects

Hodgkin's disease (HD) is characterized by the presence of the typical, clonal malignant Hodgkin and Reed-Sternberg (H-RS) cells in a hyperplastic background of normal reactive lymphocytes, plasma cells, histiocytes, neutrophils, eosinophils and stromal cells. The neoplastic nature of HD is based on aggressive clinical progression, presence of the proliferating and atypical H-RS cells, aneuploidy and cellular clonality. Immunophenotypical studies have demonstrated frequent expression of lymphoid "activation markers' including CD15, CD25, CD30, CD40, CD54, CD70, CD71, CD80, CD86 and MHC class II and less frequent expression of T- or B-cell-associated antigens by the neoplastic H-RS cells. The clonality of H-RS cells is demonstrated by clonal EBV integration, clonal cytogenetic abnormalities including p53 mutations and clonal immunoglobulin rearrangements in some HD cases. There is involvement of diverse molecules with oncogenic potential, including presence of viruses (Epstein-Barr virus and human herpes virus-6) and/or oncogenes/tumour suppressor genes (bcl-2/bcl-x, p53/MDM-2, c-myc, c-fms, N-ras, lck). The histopathological presentation and characteristic clinical features of HD correlate with an unbalanced production of multiple cytokines and define HD as a tumour of cytokine-producing cells. The proportion of malignant H-RS cells to reactive cellular components and fibrosis is dependent on the production of particular cytokines and allows subtyping of HD cases. The combined use of immunohistochemical, biochemical and molecular techniques has thus allowed recognition that HD represents more than one clinico-pathological entity with different types of H-RS cells. The defined mechanism for the biological nature, origin and oncogenesis of H-RS cells remains not fully understood, but is susceptible to further analysis using modern technology.

Pathology and "molecular histology' of Hodgkin's disease and the border to non-Hodgkin's lymphomas

HD is characterized by a small amount of tumour cells (the H- and RS-cells) in a background of many, probably reactive, lymphocytes and histiocytes. Lymphocyte predominant HD seems to be a distinct clinicopathological entity of germinal centre cell origin and has a relatively favourable prognosis. This type has to be differentiated from mixed cellularity and nodular sclerosis HD, which show a different marker profile of the H- and RS-cells and their variants. Differentiation of progressively transformed germinal centres from lymphocyte predominant HD may be problematical and is based on the detection of L&H-cells in the latter entity. Diffuse paragranuloma may be difficult to differentiate from classic HD as well as non-Hodgkin's lymphomas, especially T-cell-rich B-cell lymphomas and peripheral T-cell lymphomas. In rare cases a distinction between HD and non-Hodgkin's lymphomas may be impossible. Similar to lymphocyte predominant HD, lymphocyte depletion HD may provide difficulties in its differential diagnosis from non-Hodgkin's lymphomas. The border with anaplastic large cell lymphoma cannot be clearly drawn and may be blurred. The border between HD and non-Hodgkin lymphomas may be especially blurred in composite lymphomas, if single cell studies can demonstrate a common clonal origin of both parts of the lymphoma. Analysis of immunoglobulin or T-cell receptor variable region genes amplified by PCR from single cells picked from histological sections ("molecular histology') combines morphological characterization and identification of H- and RS-cells with a molecular analysis of those cells. This enables one not only to determine the nature of H- and RS-cells and their clonality but also to answer questions about the relationship between Hodgkin and non-Hodgkin's lymphomas.

Microwave pretreatment improves RNA-ISH in various formalin-fixed tissues using a uniform protocol

RNA is situ hybridization technique (RNA-ISH) is hampered by formalin fixation of tissues. This necessitates a pretreatment step of enzymatic digestion. However, to achieve the best results, digestion times and concentrations of enzymes have to be adapted for every specimen in a cumbersome procedure. Microwave pretreatment (MP) of formalin-fixed tissues has developed to become a powerful tool in immunohistochemistry (IHC) in recent years. To evaluate whether MP could also be helpful for RNA-ISH, we compared MP and conventional enzymatic pretreatment systematically using different tissues and various fixation times. As a model for RNA-ISH we chose the detection of kappa/lambda light chain mRNA in tonsils and lymph nodes with follicular hyperplasia and lymph nodes of patients with lymphocyte predominant Hodgkin's Disease (LPHD). Signal intensity obtained after MP was at least as good or dramatically enhanced as that obtained with optimized, single case adapted conventional pretreatment, the morphology being much better preserved after MP. These results confirm MP as a suitable method to unify the staining protocols in RNA-ISH, regardless of the duration of formalin fixation. Based on our results we recommend MP as a reliable and inexpensive method to enhance, standardized and simplify RNA-ISH.

Combination of Hodgkin's disease and diffuse large cell lymphoma: an in situ hybridization study for immunoglobulin light chain messenger RNA

It is not clear whether the rare combination of Hodgkin's diseases with non-Hodgkin lymphomas are true composite lymphomas or differentiation stages of one tumour cell clone. We used in situ hybridization and immunohistochemistry for the demonstration of immunoglobulin light chains in order to investigate the relationship between the two lymphoma components. In three cases of nodular lymphocyte predominance Hodgkin's disease combined with diffuse large B-cell lymphoma the Hodgkin cells, as well as the tumour cells in the diffuse large B-cell lymphoma, showed the same messenger RNA for one light chain. Thus, using in situ hybridization in nodular lymphocyte predominance Hodgkin's disease combined with diffuse large B-cell lymphoma in a small number of cases a possible genetic relationship between the two components could be shown. In nodular sclerosis combined with diffuse large B-cell lymphoma, in situ hybridization did not support a common clonal origin of both tumour parts. However, a unique clonal derivation cannot be excluded by the techniques applied.

Nodular type of lymphocyte predominant Hodgkin's disease. A clinical study of 50 cases

BACKGROUND

Lymphocyte predominant Hodgkin's disease (LP-HD), particularly that with a nodular pattern has been suggested to constitute a distinct disorder within the spectrum of Hodgkin's disease, this issue being based on clinical, morphological and immunological observations. Furthermore, the nodular LP-HD (N-LP-HD) has been considered to differ from the diffuse subtype (D-LP-HD), although the data are conflicting. The question addressed in this study was whether the clinical course of N-LP-HD differs from that of the D-LP-HD as well as the other subtypes of Hodgkin's disease.

PATIENTS AND METHODS

90 cases diagnosed as LP-HD at St. Bartholomew's Hospital (SBH) were reviewed. The histopathological classification was based on the original Lukes and Butler criteria for classical N-LP-HD. Clinical data were retrieved from case notes and a computer database. Stage was determined by the Ann Arbor criteria. Survival and remission duration analyses were performed for the group of patients with N-LP-HD and compared with an histological control group of patients with the other subtypes of Hodgkin's disease and the cases of LP-HD that have been reclassified.

RESULTS

1. 50/90 cases (56%) originally diagnosed as N-LP-HD qualified as N-LP-HD. No case with the diffuse subtype, could be identified. Twenty-three percent of the cases were reclassified as Mixed Cellularity and 11% as Nodular Sclerosis HD, whilst 10% as non-Hodgkin's lymphomas. 2. The majority of cases (78%) presented with early stage (I + II). Bone marrow and liver involvement were rare. 3. 92% of cases achieved complete remission. Recurrence developed in only 6/46 patients within 5-12 years. A second complete remission was achieved in 5/6 (83%) cases. Further recurrences have not yet occurred. 4. The overall survival of the 50 cases with N-LP-HD was 92% at 4 years and did not differ significantly from the 40 cases that have been reclassified. Remission duration however, was significantly better for the group of N-LP-HD being 81% at 12 years. 5. Second malignancies were common and developed in 6/50 cases (12%) with N-LP-HD within 10-15 years. These included: ALL (1 case), high grade B-NHL (2 cases), squamous cell carcinoma (1 case), glioma (1 case), lung carcinoma (1 case). 6. 12/50 patients died within a period of follow-up, up to 21 years. 1/3 of the deaths was attributed to the development of second malignancy.

CONCLUSIONS

The diffuse variant of LP-HD is rare, having not been seen at St. Bartholomew's Hospital during this time period. The 50 cases with N-LP-HD showed a favourable course with presentation at an early stage, good response to treatment, late recurrences and remission duration other than the other subtypes of HD. The latter could be attributable to the early stage at presentation of N-LP-HD, since the remission duration on a matching on stage analysis was superficially better in favour of N-LP-HD (p = 0.06). The indolent course of the disease in combination with the risk of second malignancy cases raises the question whether histology should be taken into consideration in the development of new protocols for HD.

[Hodgkin disease: recent histological and biological data]

Recent histologic, immunophenotypic and genotypic data have restricted the concept of Hodgkin's disease (HD) to the type 2 and 3 of Rye classification. This classification should be revised since the lymphocyte-predominance type has been shown to include the nodular paragranuloma which is a B-cell lymphoma, cases which have been confused with T-cell-rich large B-cell non Hodgkin's lymphoma (NHL) and cases which should be reclassified among the mixed cellularity group. Further more, most types 4 are now regarded as anaplastic large cell NHL. Immunophenotypic and genotypic studies support the heterogeneous nature of Reed-Sternberg and Hodgkin's (RSH) cells since they could be derived from B, T or null lymphocytes. In 50% of cases, RSH cells harbour the Epstein-Barr virus genome and express a viral protein, the latent membrane protein, which could play an oncogenic role in HD. Finally, RSH cells produce a wide range of cytokines that could stimulate their proliferation and explain the marked cellular reaction that is observed in HD.

Biopathologic features of Hodgkin's disease

The neoplastic nature of Hodgkin's disease (HD) is suggested by several lines of evidence, including aggressive clinical course, presence of proliferating atypical cells morphologically recognized as Hodgkin's and Reed-Sternberg cells (H-RS), aneuploidy, and, in the minority of cases, clonality. Nevertheless, the etiopathogenesis of HD still remains elusive, and probably diverse. This uncertainty is partly due to the peculiar histology of HD lesions, characterised by the paucity of the putative neoplastic cell component, i.e. H-RS cells, admixed to a variety of reactive cells which prevent an exhaustive investigation at molecular level. Nevertheless, the possible involvement of different molecules with oncogenic potential has been recently suggested on the basis of immunohistological and molecular biology studies. These include oncogenes such as bcl-2 and MDM2 and anti-oncogenes such as p53. In addition, a large amount of data has accumulated on the possible role of EBV infection in HD. The colonization of lymphoid tissues by immortalized H-RS cells can account for the derangement of cytokine networks leading to microenvironmental and systemic abnormalities. In addition, a variety of soluble receptors (sIL-2R, sCD30, sTNF-R), and adhesion molecules (sICAM-1) are abnormally produced at sites of disease involvement. Some of these molecules still retain the ability to bind their ligands and can potentially contribute to the derangement of immune mechanisms observed in HD. Many of these soluble molecules can also be found in the patient's sera providing new potential prognostic and follow-up parameters in HD patients. The comparative analysis of the same molecules within the tissue, using immunohistochemistry, and in the blood, using immunochemical assays, appears as a promising informative approach.

Hodgkin disease: Hodgkin and Reed-Sternberg cells picked from histological sections show clonal immunoglobulin gene rearrangements and appear to be derived from B cells at various stages of development

Hodgkin disease (HD) is characterized by a small number of putative malignant cells [Hodgkin and Reed-Sternberg (HRS) cells] among a background of lymphocytes and histiocytes. The lineage of HRS cells is still elusive and a clonal origin of these rare cells has not formally been demonstrated. We isolated HRS cells by micromanipulation from histological sections of three cases of Hodgkin lymphoma (each representing a distinct subtype of the disease) and analyzed individual cells for immunoglobulin variable (V) gene rearrangements by PCR. In each of the three cases a single heavy-chain V (VH) (and in one case, in addition, a kappa light-chain) gene rearrangement was amplified from the HRS cells, identifying these cells as members of a single clone. A potentially functional VH rearrangement was obtained from a case of nodular sclerosis HD. Somatic mutations and intraclonal diversity in the VH genes indicate a germinal center B-cell origin of the HRS cells in a case of lymphocyte-predominant HD, whereas in a case of mixed-cellularity HD the sequence analysis revealed only nonfunctional V gene rearrangements, suggesting a pre-B-cell origin. This indicates that HRS cells can originate from B-lineage cells at various stages of development.