Expression of the bcl-2 oncogene product and chromosomal translocation t(14;18) in Hodgkin's disease

Apoptosis and cell cycle-related genes and proteins in classical Hodgkin lymphoma: application of tissue microarray technique

The etiology and pathogenesis of Hodgkin lymphoma (HL) are not yet known. There are implications of genes involved in programmed cell death (apoptosis), and there have been repeated suggestions of an association with Epstein-Barr virus (EBV). The aim of this study was to investigate the protein expression patterns of key cell cycle-related genes, together with evidence of apoptosis and EBV status, in relation to clinical stage in HLs. A double immunohistochemical and in situ hybridization technique was used to detect the expression of bcl-2, p53, retinoblastoma (Rb), p21, Ki67 (MIB 1), and topoisomerase IIalpha (TopoIIalpha), together with latent membrane protein-1 and EBER for EBV status and TdT-mediated dUTP-FITC nick end-labeling (TUNEL) as a measure of apoptosis, on tissue microarray sections of 62 cases of classic HL (35 NS, 17 MC, 8 LR, and 2 LD). A panel of phenotypic markers was used to facilitate recognition of Hodgkin and Reed-Sternberg (H-RS) cells: CD3, CD20, CD30, CD15, and EMA. The H-RS cells of 62 classic Hodgkin lymphomas were bcl-2-positive in 35 cases (56.45%), p53-positive in 14 (22.58%), and positive for both EBV latent membrane protein-1 and EBER in 37 (59.68%); there was complete concordance of results for EBV by both procedures. No correlation was found between expression of bcl-2, p53, or EBV markers in H-RS cells and clinical stage (P > 0.05). Expression of Rb, Ki67, p21, and TopoIIalpha did, however, show significant differences with clinical stage. Expression of Rb and p21 in CD30-positive H-RS cells decreased with more advanced stage (P < 0.001). In contrast, Ki67 and ToPoIIalpha expression increased with later stage (P < 0.01). No correlation was found between expression of any of these markers in H-RS cells and the subtypes of nodular sclerosis HL, mixed cellularity HL, and LRHL (P > 0.05). TUNEL was found in the nonneoplastic cellular background in all cases and in H-RS cells in only 10 of 62 cases (16.12%) (8 nodular sclerosis HL, 1 mixed cellularity HL, and 1 LRHL). There was a significant correlation between high expression of bcl-2 and a low score by TUNEL (P < 0.05). These data are consistent with the notion that overexpression of bcl-2 may be linked to blockage of apoptosis-mediated death of H-RS cells in classic HL. Abnormal expression of p53-related protein may not play a major role in HL, because it is present in H-RS cells in only a minority of cases. Increased expression of Ki67 and TopoIIalpha by H-RS cells is significantly associated with advanced stage and may indicate aggressive disease. Adverse clinical outcome in HL also is associated with loss of Rb and p21 protein expression, consistent with the possible roles of Rb and p21 in inhibition of the growth of H-RS cells. Within the limitations of the methods used, almost two thirds of cases of HL provide evidence of an association with EBV. The tissue microarray technique is valuable not only for examination of large numbers of cases of a disease by a complex panel of markers but also potentially as a control for staining quality in immunohistochemistry and in situ hybridization.

Pathobiology of NPM-ALK and variant fusion genes in anaplastic large cell lymphoma and other lymphomas

Despite its clinical and histological heterogeneity, anaplastic large cell lymphoma (ALCL) is now a well-recognized clinicopathological entity accounting for 2% of all adult non-Hodgkin's lymphomas (NHL) and about 13% of pediatric NHL. Immunophenotypically, ALCL are of T cell (predominantly) or Null cell type; by definition, cases expressing B cell antigens are officially not included in this entity. The translocation (2;5)(p23;q35) is a recurring abnormality in ALCL; 46% of the ALCL patients bear this signature translocation. This translocation creates a fusion gene composed of nucleophosmin (NPM) and a novel receptor tyrosine kinase gene, named anaplastic lymphoma kinase (ALK). The NPM-ALK chimeric gene encodes a constitutively activated tyrosine kinase that has been shown to be a potent oncogene. The exact pathogenetic mechanisms leading to lymphomagenesis remain elusive; however, the synopsis of evidence obtained to date provides an outline of likely scenarios. Several t(2;5) variants have been described; in some instances, the breakpoints have been cloned and the genes forming a new fusion gene with ALK have been identified: ATIC-ALK, TFG-ALK and TPM3-ALK. Cloning the translocation breakpoint and identifying the ALK and NPM genes provided tools for screening material from patients with ALCL using various approaches at the chromosome, DNA, RNA, or protein level: positive signals in the reverse transcriptase-polymerase chain reaction (RT-PCR) and the immunostaining with anti-ALK monoclonal antibodies (McAb) serve as the most convenient tests for detection of the t(2;5) NPM-ALK since the fusion gene and ALK protein expression do not occur in normal or reactive lymphoid tissue. The wide range of NPM-ALK positivity reported in different series appears to be dependent on the inclusion and selection criteria of the ALCL cases studied. Overall, however, 43% of ALCL cases were NPM-ALK+ (83% of pediatric ALCL vs 31% of adult ALCL). Occasional non-ALCL B cell lymphomas (4%) with diffuse large cell and immunoblastic histology and Hodgkin's disease cases (3%) were NPM-ALK-, but these data are questionable. The aggregate results indicate that, in contrast to primary nodal (systemic) ALCL, the t(2;5) may be present in only 10-20% of primary cutaneous ALCL and rarely, if at all, in lymphomatoid papulosis, a potential precursor lesion; however, these 10-20% positive cases were not confirmed by anti-ALK McAb immunostaining and may represent an overestimate. Positivity for NPM-ALK is associated to various degrees with the following parameters: 44% and 45% of ALCL cases with T cell and Null cell immunophenotype, respectively, are positive, whereas only 8% of cases with a B cell immunoprofile are positive; the mean age of positive patients is significantly younger than that of negative patients; positive cases carry a better overall prognosis (but not in all studies). Recently, the homogenous category of ALK lymphoma ('ALKoma') has emerged as a distinct pathological entity within the heterogenous group of ALCL. The fact that patients with ALK lymphomas experience significantly better overall survival than ALK- ALCL demonstrates further that analysis of ALK expression has important prognostic implications. The term ALK lymphoma signifies a switch in the use of the diagnostic criteria: cases are selected on the basis of a genetic abnormality (the ALK rearrangement), instead of the review of morphological or immunophenotypical features which are clearly more prone to disagreement and controversy. Since its initial description in 1985 ALCL has become one of the best characterized lymphoma entities.

Evaluation of some tissue and serum biomarkers in prostatic carcinoma among Egyptian males

OBJECTIVES

The purpose of this study is to evaluate the role of soluble E-cadherin as a serum marker and bcl-2 and DNA content as tissue markers in characterization and management of prostatic adenocarcinoma (PC) among Egyptian males.

DESIGN AND METHODS

The study group included 71 patients with prostatic adenocarcinoma, 30 patients with benign prostatic hyperplasia (BPH), and 20 normal male subjects. Serum soluble E-cadherin (sE-cadherin) and PSA were quantified by ELISA and MEIA (microparticle enzyme immunoassay) techniques, respectively. Tissue samples were investigated for bcl-2 chromosomal translocation t(14;18) by polymerase chain reaction (PCR) together with detection of bcl-2 protein expression by immunohistochemistry. The results were correlated with DNA content (as defined by flow cytometric analysis) and also with traditional clinicopathologic parameters.

RESULTS

Our data revealed that, serum PSA was superior to sE-cadherin as a marker for PC with a sensitivity of 83% compared to 59% in case of E-cadherin at the same specificity (96.6%). Combination of both markers raised the sensitivity to 90%. E-cadherin correlated with Gleason score. Ploidy status, synthetic phase fraction (SPF), and proliferation index (PI) correlated significantly with tumor Gleason score. PI was also correlated to clinical stage. bcl-2 protein was overexpressed in 14% of PC and it showed a trend for correlation with tumor Gleason score (p = 0.06). We failed to detect chromosomal t(14;18) in the bcl-2 gene in all the studied tumors.

CONCLUSIONS

E-Cadherin is a clinically useful biomarker in PC specially in combination with PSA. DNA content changes and bcl-2 oncogene may account for tumorogenesis and may assist in prognostication of PC.

Apoptosis-related genes and proteins in Hodgkin's disease

During recent years it has become increasingly evident that L&H cells in nodular lymphocytic predominance (LP) Hodgkin's disease (HD) and Hodgkin and Reed-Sternberg (H-RS) cells in approximately half the cases of classical HD originate from B-lymphocytes, and that H-RS cells in most of the remaining cases of classical HD express a null phenotype. The pathogenesis of HD is unknown. An association with Epstein-Barr virus (EBV) has been suggested and there are also indications that genes involved in programmed cell death (apoptosis) may be implicated. In this study, the expression of four apoptosis-related proteins (bcl-2, bcl-x, bax and p53) in 53 cases of HD was examined and the data were correlated with the genotype, the EBV status and the phenotype (B, T or null) of the neoplastic cells. The H-RS cells expressed a B-cell phenotype in 3/3 cases of nodular LP and in 19/ 50 (38%) cases of classical HD. The remaining cases showed a null-cell phenotype in 29/50 (58%) and a T-cell phenotype in 2/50 (4%). EBV was more often positive in B (14/19, 74%) than in null (7/29, 24%) type HD. The H-RS cells were bcl-2-positive in 19/53 (36%), bcl-x-positive in 17/53 (32%), bax-positive in 1/53, and p53-positive in 41/53 (77%) cases. No relationship was found between bcl-2 expression and EBV status, or between bcl-2 and bcl-x expression. A t(14;18) translocation was seen in 2 of 34 cases. P53 point mutations were not detected. Our findings indicate that nodular LP and classical HD originate from B-cells in a high proportion of cases. They also suggest a role for bcl-2, bcl-x and p53 in tumorigenesis. The pathogenesis is not known at this stage.

Interleukin-10 levels are often elevated in serum of adults with Hodgkin's disease and are associated with inferior failure-free survival

BACKGROUND

Interleukin-10 (IL-10) is a pleiotropic cytokine that protects B- or T-lymphocytes and hemopoietic progenitors from apoptosis induced by doxorubicin, glucocorticoids, or deprivation of growth factors. IL-10 is also immunosupressive, and tumor cells secreting IL-10 can grow in syngeneic or allogeneic hosts, and can inhibit the generation of tumor-specific cytotoxic T cells. Hodgkin-Reed-Sternberg cells are derived from follicular center B cells and they may be latently infected by EBV. When this occurs they often express IL-10. Based on these considerations we investigated the relationship between pretreatment serum IL-10 levels and failure-free survival (FFS) in Hodgkin's disease (HD).

PATIENTS AND METHODS

Untreated patients, older than 16 years, with biopsy-proven HD, were included if treated with ABVD or equivalent regimens, and if pretreatment serum was available. IL-10 levels were determined with a capture enzyme-linked immunoassay specific for cellular IL-10.

RESULTS

Among healthy adult volunteers serum IL-10 levels ranged from 4.8-9.8 pg/ml (mean 7.1, standard deviation 1.5 pg/ml). Therefore levels > or = 10 pg/ml were considered elevated. We identified 101 patients with available serum. Their median age was 32 years, and 60% had B-symptoms. Ann Arbor stage was I in 4, II in 21, III in 35, and IV in 41 patients. Histology was nodular sclerosis in 74, mixed cellularity in 12, lymphocyte predominance in six, lymphocyte depletion in one, and unclassified in eight patients. Pretreatment serum IL-10 levels were elevated in 51 patients, and were higher in those with serum albumin < 3.5 g/dl, B symptoms, serum beta 2-microglobulin > or = 2.5 mg/l, anemia, and AAS III or IV. After a median follow-up of 32 months for survivors, 20 patients have progressed, and the three-year FFS of those with high vs. normal serum IL-10 was 60% +/- 9 vs. 91 +/- 9% (50% vs. 50% of the population; P = 0.004 by log-rank). Among patients with Ann Arbor stage III or IV the three-year FFS for those with high vs. normal serum IL-10 (58 vs. 42% of the population) was 57 +/- 9% vs. 92 +/- 6% (P = 0.008 by log-rank). Multivariate analysis using Cox's proportional hazards model confirmed that IL-10 was an independent variable associated with inferior FFS in this population.

CONCLUSIONS

Elevation of serum IL-10 levels is frequent and is associated with inferior FFS in adults with ABVD-treated HD. This observation should be verified in other patient populations. In addition, the source and the role of IL-10 in the biology of HD should be further investigated.

Single-Cell Analysis of the t(14;18)(q32;q21) Chromosomal Translocation in Hodgkin's Disease Demonstrates the Absence of This Translocation in Neoplastic Hodgkin and Reed-Sternberg Cells

Using the polymerase chain reaction (PCR) technique and total DNA extracts of Hodgkin's disease (HD)-involved lymph nodes, the t(14;18)(q32;q21) translocation was detected in 37 of 115 (32.2%) cases studied. No correlation was found between the presence of this translocation and bcl-2 protein expression in Hodgkin and Reed-Sternberg (HRS) cells detected by immunohistochemistry in 58 of 96 (60.4%) cases. To identify the cells carrying the t(14;18) translocation, single-cell DNA from HRS cells isolated by micromanipulation from frozen tissue sections of lymph nodes was investigated by PCR amplification. Eleven cases showing a positive band of the same size in at least two of five PCR experiments performed on the same total DNA extract were selected for single-cell PCR. We postulated that this repeated successful amplification could be indicative of the presence of the t(14;18) translocation in the neoplastic HRS cells. Single cells from frozen tumor sections of the t(14;18)-positive OCI LY8 cell line grafted into nude mice served as a positive control. The bcl-2/JH rearrangement, involved in this translocation, could be amplified from single-cell DNA of the latter tumor, whereas, in all of the HD cases, HRS cells were found to be negative. We conclude that the t(14;18) translocation is not localized in HRS cells, but in nonmalignant B bystander lymphocytes, admixed with these neoplastic cells.

The mummified Hodgkin cell: cell death in Hodgkin's disease

This study attempts to define more clearly the morphology and ultrastructure of mummified Hodgkin cells, to determine their incidence in the different histological subtypes of Hodgkin's disease (HD), and to correlate these data with the expression of p53, bcl-2, mdm2, and p21/WAF1. Forty-five cases of primary HD were examined at light and electron microscopic level. DNA strand breaks were detected by the in situ end-labelling (ISEL) and the TdT-mediated dUTP-digoxigenin nick end-labelling (TUNEL) technique. Mummified Hodgkin cells display morphological features that differ from those of classical apoptosis. In contrast to apoptotic cells, mummified Hodgkin and Reed-Sternberg (HRS) cells do not react in the ISEL or TUNEL procedures and maintain the expression of antigens such as CD30 and CD15. The morphology of mummified tissue cells could be simulated by CD95-mediated induction of apoptosis in the Hodgkin cell line HDLM2 if internucleosomal DNA fragmentation was inhibited by zinc ions. The highest incidence of mummified cells was found in the nodular sclerosis and mixed cellularity subtypes, whereas the lowest frequency was observed in nodular paragranuloma. The frequency was independent of p53, bcl-2, p21, and mdm2 expression. p21 and mdm2 immunoreactivity of HRS cells was correlated with p53 status. HRS cells in nodular paragranuloma were virtually negative for p21/WAF1 or bcl-2. Classical apoptotic cells reacting in the TUNEL and ISEL procedures are found in all subtypes of HD and are derived from the non-neoplastic cellular background. In conclusion, mummified Hodgkin cells display features of apoptosis lacking the internucleosomal DNA fragmentation. The pattern of the p53-transactivated genes mdm2 and p21/WAF1 suggests that inactivating mutations of p53 are rare in HD.

Epstein-Barr virus infection, Hodgkin's disease, non-Hodgkin's lymphoma, and reactive follicular hyperplasia in Japanese children: evaluation of paraffin-embedded specimens using polymerase chain reaction and immunohistochemistry

Epstein-Barr virus (EBV) infections are common in Japanese children, with infectious by EBV type 1. The relationships between EBV infection and lymphadenopathies in Hodgkin's disease (HD), non-Hodgkin's lymphomas (NHL), reactive follicular hyperplasia (RFH), and infectious mononucleosis (IM) in 37 Japanese children were evaluated. Formalin-fixed, paraffin-embedded lymph node specimens that were obtained at surgical resection or biopsy were evaluated for the presence of EBV DNA and the latent membrane protein-1 (LMP-1) using polymerase chain reaction (PCR) and immunohistochemical staining. The PCR detected EBV DNA in nine of 13 (69.2%) patients with RFH, including a case of IM, all three (100%) patients with HD, and one of 21 (4.8%) patients with NHL. All EBV-positive samples contained EBV type 1. Reed-Sternberg's cells in HD were immunohistochemically positive for LMP-1, whereas all cases of RFH and NHL were negative for LMP-1. Results suggest that EBV infection may be related to HD. Although no proof exists that EBV infection contributes to the transformation of cells, thus causing RFH or NHL, the present authors suggest that the EBV-positive cases in Japanese children demonstrate a relationship between the clinical and histopathological features of the lymphadenopathy and EBV-type 1 infection.

Phenotype of Hodgkin and Sternberg-Reed cells and expression of CD57 (LEU7) antigen

Possible associations between the immunophenotype of Hodgkin (H) and Sternberg-Reed (S-R) cells, the expression of CD57 (Leu 7) antigen, and the presence of Epstein-Barr virus (EBV) were investigated in lymph node specimens from 50 cases of Hodgkin's disease (HD), including 26 cases of mixed cellularity and 24 cases of nodular sclerosis. Tissues were fixed in 10% neutral formalin, or/and B5 solution. H and S-R cells were CD30+, CD15+ (85% of the cases) and LCA (CD45). A proportion of neoplastic cells positive for either T-cell markers (CD3) or B-cell markers (CD20) was observed in 10% and 34% of the cases, respectively. Membrane positivity for CD57 antigen was found in H and S-R cells in 10 cases (8 cases of mixed cellularity, and 2 cases of nodular sclerosis). Such immunopositivity was only observed in B5-fixed sections. No staining for CD57 antigen was identified in H and S-R cells of any case with CD20 positive neoplastic cells. H and S-R cells of both CD57-positive and CD57-negative cases were further studied by immunohistochemistry for LMP1, by in-situ hybridization for EBER and by polymerase chain reaction (PCR) for EBV-DNA. No association was identified between the expression of CD57 antigen and the presence of EBV sequences, transcripts or proteins. Our findings do not support a B-cell origin for H and S-R cells in CD57-positive cases of Hodgkin's disease and suggest that these neoplastic cells may be related to natural killer (NK) or T-cells expressing CD57 antigen.

Bcl-2 oncoprotein is widespread in lymphoid tissue and lymphomas but its differential expression in benign versus malignant follicles and monocytoid B-cell proliferations is of diagnostic value

The distribution of Bcl-2 oncoprotein was studied immunohistochemically in formaldehyde-fixed and paraffin-embedded reactive and neoplastic lymphoid tissue. The potential of Bcl-2 for the differential diagnosis of follicular lesions was emphasized, and the results on follicular lesions were correlated with those of polymerase chain reaction (PCR) assay of the immunoglobulin heavy chain gene rearrangement. In hyperplastic lymphoid tissue, Bcl-2 reactivity was widespread, including germinal center surroundings, scattered cells within the germinal centers, and the T-cell areas in general. Distinctively negative lymphoid populations included the majority of germinal center cells, and the negative staining pattern was maintained in cases of florid hyperplasia. In contrast, follicular lymphoma cells were consistently Bcl-2 positive. The immunohistochemical Bcl-2 reactivity of lymphoma follicles correlated with the clonal PCR amplification pattern of the immunoglobulin heavy chain gene; all Bcl-2-negative hyperplasias revealed a non-clonal pattern. Clusters of monocytoid B cells were Bcl-2 negative, whereas monocytoid B-cell lymphomas and closely related MALT lymphomas were positive. All other small cell non-Hodgkin's lymphomas of B-cell types showed nearly uniform Bcl-2 reactivity, whereas large cell B-cell lymphomas were variably positive (74%). In Hodgkin's cells, Bcl-2 reactivity was seen in the neoplastic populations of most cases of nodular sclerosis and mixed cellularity types, whereas the L&H and Reed-Sternberg cells in lymphocyte predominance Hodgkin's disease were negative in most cases. Bcl-2 immunohistochemistry thus appears very valuable in the differential diagnosis of follicular hyperplasia and neoplasia, and it may help to distinguish between reactive and neoplastic monocytoid B cells. However, Bcl-2 immunohistochemistry is not useful in the subtyping of B-cell lymphomas.

Low incidence of mbr bcl-2/JH fusion genes in Hodgkin's disease

Lymph node biopsies from 140 cases of Hodgkin's disease (HD) and from 30 non-malignant lesions were screened for the presence of t(14;18) translocations involving the major breakpoint region (mbr) of the bcl-2 gene and the joining region (JH) of the immunoglobulin heavy chain gene, using a polymerase chain reaction (PCR) assay with subsequent nucleotide sequencing of amplified bcl-2/JH junctional regions. Expression of the bcl-2 protein within the Hodgkin and Reed-Sternberg (HRS) cells was investigated in 86 cases of HD by immunohistochemistry on cryostat or paraffin sections. Although bcl-2 expression could be found in a proportion of neoplastic cells in up to one-third of HD cases, the frequency of t(14;18) gene fusions detected by PCR was low. We identified such gene fusions in only 3 out of 140 (2 per cent) HD cases, one biopsy of which presented with four clonally distinct bcl-2/JH sequences. No t(14;18) was found in any of 30 reactive lymph node lesions. All fusion gene sequences were unique regarding the localization of the chromosome 14 and 18 breakpoints and the extranucleotide N-insertions. None of these gene fusions conformed to t(14;18) breakpoint sequences previously characterized in our laboratories. Our findings point to a mere coincidence in some cases of HD lesions and cells carrying a t(14;18) in the same biopsy and argue against a significant role of bcl-2 in the pathogenesis of HD.

The bcl-2/JH gene rearrangement is undetectable in Hodgkin's lymphomas: results from the German Hodgkin trial

Ninety-one Hodgkin's lymphomas (HD), 52 non-Hodgkin lymphomas (NHL) and 33 specimens of non-neoplastic lymphatic tissues were investigated by polymerase chain reaction (PCR) for the presence of the bcl-2/JH gene rearrangement. The majority of the HD cases were drawn from the files of the German Hodgkin trial where diagnoses are established by a panel of four independent histopathologists. Using the very sensitive PCR method which detected 1 positive among 10000 negative cells, the bcl-2/JH gene rearrangement was found in 7/52 NHL and 3/16 tonsils with follicular hyperplasia, but in none of the 91 HD. The bcl-2 protein, however, was expressed by malignant cells of B and T cell lymphomas and by the giant tumour cells in 2/13 HD lymphocyte predominant, 11/28 HD nodular sclerosing I, 14/17 HD nodular sclerosing II, 10/27 HD mixed cellularity and 3/3 HD lymphocyte depleted. The bcl-2/JH rearrangement is thus independent of protein over-expression, the latter being found in all types of lymphomas. Our results do not confirm the findings of others who have detected the bcl-2/JH rearrangement in HD. These discrepancies may be explained by differences in choice of material, the gene rearrangement actually occurring in bystander cells but not in Reed-Sternberg or Hodgkin cells, or by contamination.

Incidence of Epstein-Barr virus bcl-2 expression and chromosomal translocation t(14;18) in large cell lymphoma associated with paragranuloma (lymphocyte-predominant Hodgkin's disease)

Seven cases of large cell lymphoma (LCL) developing simultaneously or secondarily to lymphocyte-predominant Hodgkin's disease (nodular paragranuloma [NP]) were investigated for the presence of Epstein-Barr virus genomic material and the chromosomal translocation t(14;18) involving the major breakpoint region of the bcl-2 gene using the polymerase chain reaction on paraffin-embedded material. The translocation t(14;18) and Epstein-Barr virus could not be demonstrated in any case. The expression of the bcl-2 oncogene product was investigated using immunohistochemistry. Only in one case were the lymphocytic and histiocytic cells positively stained with the bcl-2 antibody, whereas the associated LCL demonstrated a completely negative immunoreaction. In another case the LCL had a positive immunoreaction with this antibody and the corresponding lymphocytic and histiocytic cells were completely negative. We conclude that Epstein-Barr virus infection is rare or absent in NP and in the LCLs associated with NP. The chromosomal translocation t(14;18) does not seem to be a factor in the transformation of NP into LCL.

Oncogenes in Hodgkin's disease

The following manuscript reviews data presented at the Cologne meeting relating to oncogene expression in Hodgkin's disease. Presented data ranged from investigations of oncogene expression in cell lines, where transcripts of unique size were identified and lineage related expressions of transcription factors described to detailed cytogenetic investigations of fresh Hodgkin's biopsy tissue. Particular attention was centred on discrepancies in the described expression of t(14; 18) and the molecular demonstration of translocated bcl-2 breakpoints in Hodgkin's disease. A large volume of data was presented relating to the relative expression of bcl-2 breakpoints by either genomic hybridization or hybridization following DNA amplification, the expression of the bcl-2 protein or the defined cytogenetic presence of the translocation. Certain other cytogenetic abnormalities of interest in Hodgkin's disease were discussed.