Anaplastic large cell lymphoma: a clinicopathologic analysis

Transformation of CLL to ALCL: the role of clonality studies in diagnostic molecular haematopathology

Clonality studies greatly assist in the diagnosis of challenging haematopathology cases. These robust and standardised tests aid the detection of clonal lymphoid populations and may assist in lymphocyte subtyping. In this case report, a gentleman presented with a high-grade transformation of a B cell neoplasm which histologically and immunophenotypically mimicked a T cell anaplastic large-cell lymphoma. With the aid of T cell and B cell receptor clonality studies, it was demonstrated that this tumour was in fact of B cell lineage. This report exemplifies the role of these increasingly used and relatively new molecular tests in unusual and difficult lymphoma presentations and highlights potential pitfalls in the interpretation of their results.

Risk assessment in the management of newly diagnosed classical Hodgkin lymphoma

Treatment of Hodgkin lymphoma is associated with 2 major types of risk: that the treatment may fail to cure the disease or that the treatment will prove unacceptably toxic. Careful assessment of the amount of the lymphoma (tumor burden), its behavior (extent of invasion or specific organ compromise), and host related factors (age; coincident systemic infection; and organ dysfunction, especially hematopoietic, cardiac, or pulmonary) is essential to optimize outcome. Elaborately assembled prognostic scoring systems, such as the International Prognostic Factors Project score, have lost their accuracy and value as increasingly effective chemotherapy and supportive care have been developed. Identification of specific biomarkers derived from sophisticated exploration of Hodgkin lymphoma biology is bringing promise of further improvement in targeted therapy in which effectiveness is increased at the same time off-target toxicity is diminished. Parallel developments in functional imaging are providing additional potential to evaluate the efficacy of treatment while it is being delivered, allowing dynamic assessment of risk during chemotherapy and adaptation of the therapy in real time. Risk assessment in Hodgkin lymphoma is continuously evolving, promising ever greater precision and clinical relevance. This article explores the past usefulness and the emerging potential of risk assessment for this imminently curable malignancy.

Advances in understanding the pathogenesis of systemic anaplastic large cell lymphomas

The currently used 2008 World Health Organization classification recognizes two types of systemic anaplastic large T cell lymphoma according to ALK protein expression in tumour cells. First, the 'anaplastic large cell lymphoma, ALK positive' (ALK(+) ALCL) that is characterized by the presence of ALK gene rearrangements and consequent ALK protein expression, and, second, the 'anaplastic large cell lymphoma, ALK negative' (ALK(-) ALCL) that is a provisional entity lacking ALK protein expression but cannot be distinguished morphologically from ALK(+) ALCL. In this review we summarize the current knowledge on the genetic lesions and biological features that underlie the pathogenesis of ALK(+) and the ALK(-) ALCL and that can lead to the use of targeted anti-cancer agents.

Signal transducer and activator of transcription 3 is a transcriptional factor regulating the gene expression of SALL4

Both signal transducer and activator of transcription 3 (STAT3) and SALL4 are important in maintaining the pluripotent and self-renewal state of embryonic stem cells. We hypothesized that STAT3, a latent transcriptional factor, may regulate the gene expression of SALL4. In support of this hypothesis, DNA sequence analysis of the SALL4 gene promoter revealed four putative STAT3-binding sites. Using a SALL4-luciferase reporter gene assay, we found that modulation of the STAT3 activity significantly up-regulated the luciferase activity. By chromatin immunoprecipitation, the segment of the SALL4 promoter showing the highest affinity to STAT3 was localized to -366 to -163, in which there was only one putative STAT3 binding site starting at -199. Site-directed mutagenesis of all four putative STAT3-binding sites in the SALL4 promoter significantly reduced its responsiveness to STAT3, although the most dramatic effect was seen at the binding site starting at -199. We further tested the functional relationship between STAT3 and SALL4 using MDA-MB-231, a breast cell line carrying constitutive SALL4 expression and STAT3 activity. Down-regulation of the STAT3 activity using a dominant-negative construct resulted in a significant decrease in the expression of SALL4. To conclude, our data suggest that STAT3 and SALL4 probably cooperate in both physiological and pathological states.

Primary systemic anaplastic large cell lymphoma in Korean adults: 11 years' experience at Asan Medical Center

PURPOSE

Anaplastic large cell lymphoma (ALCL), a CD30+ T-cell non-Hodgkin's lymphoma, represents only 2-8% of lymphoma overall. Information on the clinical findings of primary systemic ALCL in Korea is limited. Our aims were to report the clinical features and outcomes of primary systemic ALCL.

PATIENTS AND METHODS

We retrospectively reviewed the medical records of 36 adult patients diagnosed with primary systemic ALCL at Asan Medical Center from February 1995 through June 2006.

RESULTS

Of 36 patients, 29 were male. The median age was 39 years (range, 17-67 years), and 26 (72%) presented with Ann Arbor stages III and IV. The most commonly involved extranodal sites were bone (n = 7) and soft tissue (n = 6). Thirty-two of all patients (89%) were treated with an anthracycline-based regimen including cyclophosphamide/doxorubicin/vincristine/prednisone (CHOP) as induction chemotherapy; 16 (50%) achieved complete remission (CR), and 13 (41%) achieved partial remission (PR). Median overall survival (OS) and event-free survival (EFS) were 49 and 17 months, respectively. Univariate analysis showed that performance status (p = 0.035), international prognostic index (IPI) (p = 0.025), and age-adjusted IPI (p = 0.034) were significant prognostic factors for OS, whereas anaplastic lymphoma kinase (ALK) expression did not affect OS (p = 0.483).

CONCLUSION

Our retrospective analysis of Korean primary systemic ALCL patients showed that median OS was 49 months and overall response to CHOP was 91%. Performance, IPI, and age-adjusted IPI were predictors of OS, whereas ALK expression did not have prognostic significance.

Development of anaplastic lymphoma kinase (ALK) small-molecule inhibitors for cancer therapy

Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase (RTK) involved in the genesis of several human cancers; indeed, ALK was initially identified in constitutively activated and oncogenic fusion forms--the most common being nucleophosmin (NPM)-ALK--in a non-Hodgkin's lymphoma (NHL) known as anaplastic large-cell lymphoma (ALCL) and subsequent studies identified ALK fusions in the human sarcomas called inflammatory myofibroblastic tumors (IMTs). In addition, two recent reports have suggested that the ALK fusion, TPM4-ALK, may be involved in the genesis of a subset of esophageal squamous cell carcinomas. While the cause-effect relationship between ALK fusions and malignancies such as ALCL and IMT is very well established, more circumstantial links implicate the involvement of the full-length, normal ALK receptor in the genesis of additional malignancies including glioblastoma, neuroblastoma, breast cancer, and others; in these instances, ALK is believed to foster tumorigenesis following activation by autocrine and/or paracrine growth loops involving the reported ALK ligands, pleiotrophin (PTN) and midkine (MK). There are no currently available ALK small-molecule inhibitors approved for clinical cancer therapy; however, recognition of the variety of malignancies in which ALK may play a causative role has recently begun to prompt developmental efforts in this area. This review provides a succinct summary of normal ALK biology, the confirmed and putative roles of ALK fusions and the full-length ALK receptor in the development of human cancers, and efforts to target ALK using small-molecule kinase inhibitors.

Individualized target therapy of malignant lymphomas: an outlook

Hodgkin and non-Hodgkin lymphomas represent clonal malignant expansions of B or T cells that are at various stages of maturation. As our understanding of the immunophenotype, cytogenetics and molecular biology of the lymphomas broadened, treatment of these neoplasms is evolving to include targeted therapies directed against tumour-characteristic molecules and specific signalling pathways critical to lymphomagenesis.

The NPM-ALK tyrosine kinase mimics TCR signalling pathways, inducing NFAT and AP-1 by RAS-dependent mechanisms

Nucleophosmin-anaplastic lymphoma kinase (NPM-ALK) expression is associated with the lymphoid malignancy anaplastic large cell lymphoma (ALCL) and results from a t(2;5) chromosomal translocation. We show that NPM-ALK induces Ras activation and phosphorylation of the ERK MAP Kinase consistent with activation of the Ras-MAP Kinase pathway. Furthermore, we demonstrate that activation of Ras is necessary for inducing transcription via NFAT/AP-1 composite transcriptional binding sites. This activity is dependent on NPM-ALK forming complexes with proteins that bind to autophosphorylated tyrosine residues at positions 156, 567 and 664, associated with binding to IRS-1, Shc and PLCgamma, respectively. Specifically, NPM-ALK activates transcription from the TRE promoter element, an AP-1 binding region, an activity dependent on both Ras and Shc activity. Our results show that NPM-ALK mimics activated T-cell receptor signalling by inducing pathways associated with the activation of NFAT/AP-1 transcription factors that bind to promoter elements found in a broad array of cytokine genes.

Anaplastic lymphoma kinase and its signalling molecules as novel targets in lymphoma therapy

A crucial issue in the development of molecularly-targeted anticancer therapies is the identification of appropriate molecules whose targeting would result in tumour regression with a minimal level of systemic toxicity. Anaplastic lymphoma kinase (ALK) is a transmembrane receptor tyrosine kinase, normally expressed at low levels in the nervous system. As a consequence of chromosomal translocations involving the alk gene (2p23), ALK is also aberrantly expressed and constitutively activated in approximately 60% of CD30+ anaplastic large cell lymphomas (ALCLs). Due to the selective overexpression of ALK in tumour cells, its direct involvement in the process of malignant transformation and its frequent expression in ALCL patients, the authors recognise ALK as a suitable candidate for the development of molecularly targeted strategies for the therapeutic treatment of ALK-positive lymphomas. Strategies targeting ALK directly or indirectly via the inhibition of the protein networks responsible for ALK oncogenic signalling are discussed.

Restoration of shp1 expression by 5-AZA-2'-deoxycytidine is associated with downregulation of JAK3/STAT3 signaling in ALK-positive anaplastic large cell lymphoma

Anaplastic lymphoma kinase (ALK)-positive anaplastic large cell lymphoma (ALK+ ALCL) is characterized by constitutive activation of the Janus kinase (JAK)3/signal transducers and activators of transcription 3 (STAT3) signaling pathway. SHP1, a tyrosine phosphatase that negatively regulates JAK/STAT, is frequently absent in ALK+ ALCL owing to gene methylation. To test the hypothesis that loss of SHP1 contributes to JAK3/STAT3 activation in ALK+ ALCL cells, we induced SHP1 expression using 5-aza-2'-deoxycytidine (5-AZA), an inhibitor of DNA methyltransferase, in ALK+ ALCL cell lines, and correlated with changes in the JAK3/STAT3 pathway. 5-AZA gradually restored SHP1 expression in Karpas 299 and SU-DHL-1 cells over 5 days. The initially low level of SHP1 expression did not result in significant changes to the expression or tyrosine phosphorylation of JAK3 and STAT3. However, higher levels of SHP1 seen subsequently correlated with substantial decreases in JAK3 and pJAK3, followed by pSTAT3 (but not STAT3). Importantly, the decrease in JAK3 was abrogated by MG132, a proteasome inhibitor. 5-AZA induced no significant increase in apoptosis but it sensitized ALCL cells to doxorubicin-induced apoptosis. Our findings support the concept that loss of SHP1 contributes to the constitutive activation of JAK3/STAT3 in ALK+ ALCL cells. SHP1 appears to downregulate JAK3 by two mechanisms: tyrosine dephosphorylation and increased degradation via the proteasome pathway.

Loss of SHP1 enhances JAK3/STAT3 signaling and decreases proteosome degradation of JAK3 and NPM-ALK in ALK+ anaplastic large-cell lymphoma

Previous studies showed that most cases of ALK(+) anaplastic large-cell lymphoma (ALK(+)ALCL) do not express SHP1, a tyrosine phosphatase and an important negative regulator for cellular signaling pathways such as that of JAK/STAT. To fully assess the biologic significance of loss of SHP1 in ALK(+)ALCL, we transfected SHP1 plasmids into 2 SHP1(-), ALK(+)ALCL cell lines, Karpas 299 and SU-DHL-1. After 24 hours of transfection, pJAK3 and pSTAT3 were decreased, and these changes correlated with down-regulation of STAT3 downstream targets including cyclin D3, mcl-1, and bcl-2. Expression of SHP1 in these 2 cell lines also resulted in marked decreases in the protein levels of JAK3 and NPM-ALK, and these effects were reversible by proteosome inhibitor MG132. Conversely, when SHP1 expression in SUP-M2 (a SHP1(+) ALK(+)ALCL cell line) was inhibited using siRNA, pSTAT3, pJAK3, JAK3, and NPM-ALK were all up-regulated. Coimmunoprecipitation studies showed that SHP1 was physically associated with JAK3 and NPM-ALK. SHP1 expression in Karpas 299 and SU-DHL-1 led to significant G(1) cell cycle arrest but not apoptosis. To conclude, loss of SHP1 contributes to the pathogenesis of ALK(+)ALCL by 2 mechanisms: (1) it leaves the tyrosine phosphorylation and activation of JAK3/STAT3 unchecked and (2) it decreases proteosome degradation of JAK3 and NPM-ALK.

High expression of calcium-binding proteins, S100A10, S100A11 and CALM2 in anaplastic large cell lymphoma

Anaplastic large cell lymphomas (ALCL) are characterised by the presence of CD30-positive large cells, which usually are of T-cell type. Based on the presence or absence of translocations involving the anaplastic lymphoma kinase (ALK) locus, ALCL cases can be divided into two groups. To gain more insight in the biology of ALCL, we applied serial analysis of gene expression (SAGE) on the Karpas299 cell line and identified 25 up- and 19 downregulated genes. Comparison of the differentially expressed genes with DNA copy number changes in Karpas299 revealed that two overexpressed genes, S100A10 and S100A11, were located in an amplicon suggesting that the increased mRNA levels were caused by DNA amplification. Quantitative reverse transcription polymerase chain reaction on 5 ALCL cell lines and 12 ALCL tissues confirmed the SAGE data for 13 out of 14 up- and one out of four downregulated genes. Immunohistochemical staining confirmed the presence of S100A10, a calcium-binding protein, in three out of five ALK+ and all 7 ALK- ALCL cases. S100A11 staining was confirmed in all ALK+ and six of seven ALK- ALCL cases. Three of the upregulated genes represented calcium-binding proteins, which suggest that altered intracellular signaling might be associated with the oncogenesis of ALCL.

High expression of Mcl-1 in ALK positive and negative anaplastic large cell lymphoma

AIM

To gain more insight into the genes involved in the aetiology and pathogenesis of anaplastic large cell lymphoma (ALCL).

METHODS

Serial analysis of gene expression (SAGE) was undertaken on the CD4+ALK+ (anaplastic lymphoma kinase positive) ALCL derived cell line Karpas299 and as comparison on CD4+ T cells. Quantitative reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemistry were performed on five ALCL derived cell lines and 32 tissue samples to confirm the SAGE data.

RESULTS

High expression of Mcl-1 was seen in the Karpas299 cell line, whereas the two other antiapoptotic Bcl-2 family members, Bcl-2 and Bcl-X(L), were not detected in the SAGE library. Quantitative RT-PCR confirmed the high expression of Mcl-1 mRNA and low expression of Bcl-2 and Bcl-X(L) in Karpas299 and in four other ALCL cell lines. To expand on these initial observations, primary tissue samples were analysed for Mcl-1, Bcl-X(L), and Bcl-2 by immunohistochemistry. All 23 ALK+ and nine ALK- ALCL cases were positive for Mcl-1. Bcl-2 and Bcl-X(L) were expressed infrequently in ALK+ ALCL cases, but were present in a higher proportion of ALK- ALCL cases.

CONCLUSION

The consistent high expression of Mcl-1 in ALK+ and ALK- ALCL suggests that Mcl-1 is the main antiapoptotic protein in this disease. The high frequency of Mcl-1, Bcl-2, and Bcl-X(L) positive ALCL cases in the ALK- group compared with the ALK+ group indicates that ALK induced STAT3 activation is not the main regulatory pathway in ALCL.

Anaplastic lymphoma kinase proteins in growth control and cancer

The normal functions of full-length anaplastic lymphoma kinase (ALK) remain to be completely elucidated. Although considered to be important in neural development, recent studies in Drosophila also highlight a role for ALK in gut muscle differentiation. Indeed, the Drosophila model offers a future arena for the study of ALK, its ligands and signalling cascades. The discovery of activated fusion forms of the ALK tyrosine kinase in anaplastic large cell lymphoma (ALCL) has dramatically improved our understanding of the pathogenesis of these lymphomas and enhanced the pathological diagnosis of this subtype of non-Hodgkin's lymphoma (NHL). Likewise, the realisation that a high percentage of inflammatory myofibroblastic tumours express activated-ALK fusion proteins has clarified the causation of these mesenchymal neoplasms and provided for their easier discrimination from other mesenchymal-derived inflammatory myofibroblastic tumour (IMT) mimics. Recent reports of ALK expression in a range of carcinoma-derived cell lines together with its apparent role as a receptor for PTN and MK, both of which have been implicated in tumourigenesis, raise the possibility that ALK-mediated signalling could play a role in the development and/or progression of a number of common solid tumours. The therapeutic targeting of ALK may prove to have efficacy in the treatment of many of these neoplasms.

Posttransplant lymphoproliferative disorder presenting as CD30+, ALK+, anaplastic large cell lymphoma in a child

We report a 15-year-old cardiac transplant recipient who developed a monomorphic posttransplant lymphoproliferative disorder (PTLPD) which demonstrated morphological and immunohistochemical features of anaplastic large cell lymphoma including CD30 and anaplastic lymphoma kinase (ALK) immunopositivity but lacking the commonly associated t(2;5) translocation. The neoplastic cells were Epstein-Barr Virus (EBV)-negative. T-cell PTLPD is an uncommon but recognized late complication in solid organ transplant recipients. This is the first reported case, to our knowledge, of PTLPD occurring in childhood with an ALK+, CD30+ anaplastic large cell lymphoma phenotype.

The new World Health Organization classification of lymphomas: the past, the present and the future

The REAL Classification of lymphomas, proposed in 1994, represents a new paradigm in lymphoma classification, consisting of a list of biologic entities defined by clinicopathologic and immunogenetic features. The non-Hodgkin's lymphomas comprise precursor lymphoblastic and mature cell neoplasms of B, T or putative natural killer cell lineage. An individual entity can exhibit a range of morphologic appearances and a range of clinical behavior. The categories in Hodgkin's lymphomas are identical to the widely used Rye classification except for the additional of a new category termed 'lymphocyte-rich classical Hodgkin's lymphoma'. The REAL classification has been validated by a major multi-institutional study involving 1378 cases (The Non-Hodgkin's Lymphoma Classification Project), showing that it is both reproducible and clinically relevant. The new World Health Organization classification of hematopoietic and lymphoid tumors, to be published in 2001, is a joint project of the Society for Hematopathology and European Association of Hematopathologists, under the auspices of the World Health Organization. This classification includes not only lymphoid neoplasms, but also myeloid, histiocytic and mast cell neoplasms. The lymphoma component of the classification is merely an update of the REAL classification, with minor changes necessitated by new information that has become available since its proposal. A conceptual grouping of the non-Hodgkin's lymphomas into four categories (indolent, aggressive, highly aggressive, and localized indolent) is also presented in this review. The next major impetus influencing the approach to lymphoma classification will no doubt be molecular genetics, in particular DNA microarrays, which will yield an enormous amount of new data that will aid in the understanding of lymphomas.

Translocations involving anaplastic lymphoma kinase (ALK)

Anaplastic large-cell lymphoma (ALCL) comprises a group of non-Hodgkin's lymphomas (NHLs) that were first described in 1985 by Stein and co-workers and are characterized by the expression of the CD30/Ki-1 antigen (Stein et al., 1985). Approximately half of these lymphomas are associated with a typical chromosomal translocation, t(2;5)(p23;q35). Much confusion about the exact classification and clinicopathological features of this subgroup of NHL was clarified with the identification of NPM-ALK (nucleophosmin-anaplastic lymphoma kinase) as the oncogene created by the t(2;5) (Morris et al., 1994). With the discovery of NPM-ALK as the specific lymphoma gene mutation, this NHL subtype could be redefined on the molecular level. This achievement was enhanced by the availability of specific antibodies that recognize ALK fusion proteins in paraffin-embedded lymphoma tissues. Several excellent recent reviews have summarized the histopathological and molecular findings of ALCL and their use in the classification of this lymphoma entity (Anagnostopoulos and Stein, 2000; Benharroch et al., 1998; Drexler et al., 2000; Foss et al., 2000; Gogusev and Nezelof, 1998; Kadin and Morris, 1998; Ladanyi, 1997; Morris et al., 2001; Shiota and Mori, 1996; Skinnider et al., 1999; Stein et al., 2000). This review will focus on the molecular function and signal transduction pathways activated by ALK fusion oncogenes, with recent advances and possible clinical implications to be discussed.

Primary systemic anaplastic large-cell lymphoma (CD30+): advances in biology and current therapeutic approaches

In 1985, Stein et al demonstrated the expression of the lymphoid activation antigen CD30/Ki by neoplastic cells. Fifteen years after the first description, anaplastic large-cell lymphomas (ALCL) are now thought to be a heterogeneous group in terms of their clinical, morphologic, phenotypic, cytogenetic, and molecular biology features. However, on the basis of a specific genetic anomaly and expression of a chimeric nucleophosmin anaplastic lymphoma kinase (NPM-ALK) protein and its variants, a distinct clinicopathologic entity defined as "ALK-positive lymphoma" or "ALKoma" can be recognized. Based on molecular and clinical criteria, 3 entities of primary ALCL can be identified: primary systemic ALK positive, primary systemic ALK negative, and primary cutaneous ALCL. This review focuses on advances in the knowledge of primary systemic ALCL biology and discusses therapeutic approaches based on ALK expression. The presence of this protein appears to be an important prognostic factor and, combined with an age-adjusted International Prognostic Index, could allow researchers to design more specific clinical trials aimed at finding new, more efficacious and less toxic treatments.

Timely topic: anaplastic lymphoma kinase (ALK) spreads its influence

Anaplastic lymphoma kinase (ALK) is normally not expressed in human tissues except selected sites in the nervous system. Its expression and constitutive activation as a result of a chromosomal translocation involving 2p23 plays a pivotal role in the genesis of anaplastic large cell lymphoma. ALK expression has been instrumental in defining a homogeneous subset from the category of anaplastic large cell lymphoma, characterised by occurrence in young patients, primary systemic presentation, favorable prognosis, a broad morphological spectrum, nuclear and/or cytoplasmic immunostaining for ALK protein, and a number of possible fusion partner genes such as NPM, ATIC, TFG, TPM3 and CLTCL. Recently ALK has been implicated in the genesis of another tumour type, the inflammatory myofibroblastic tumours. The ALK-positive examples occur in children and young adults, involving a variety of sites, such as the abdomen, mesentery, liver, bladder, mediastinum, lung and bone. The partner genes identified in some cases are TPM3 (tropomyosin 3) and TPM4 (tropomyosin 4). These molecular findings also further support the neoplastic nature of at least a subset of inflammatory myofibroblastic tumours.

Recurring chromosomal abnormalities in non-Hodgkin's lymphoma: biologic and clinical significance

Non-Hodgkin's lymphomas (NHLs) are a group of clinically important neoplasms with a complex biology that makes their classification and treatment difficult. Their incidence is increasing and they cause significant morbidity and mortality. NHLs result from transformation of B and T/natural killer (NK) cells. Their genetic hallmark is chromosomal translocations resulting from aberrant rearrangements of IG and TCR genes, which lead to inappropriate expression of genes at reciprocal breakpoints that regulate a variety of cellular functions, including gene transcription, cell cycle, apoptosis, and tumor progression. Cytogenetics followed by molecular genetic analysis of some of the recurring translocations continues to provide new insights into lymphomagenesis and cell biology. More recently, chromosomal and gene amplification and gene deletion have been recognized as frequent genetic changes that may play a role in lymphoma progression and clinical behavior. In this review, cytogenetic data pertaining to recurring chromosomal changes on lymphomas are reviewed and examined in relation to their relevance to lymphoma development, classification, and clinical behavior.

Non-Hodgkin's Lymphoma: Molecular Features of B Cell Lymphoma

The rapid increase in the incidence of the B cell non-Hodgkin's lymphomas (NHL) and improved understanding of the mechanisms involved in their development renders timely a review of the theoretical and practical aspects of molecular abnormalities in B cell NHL.

In Section I, Dr. Macintyre addresses the practical aspects of the use of molecular techniques for the diagnosis and therapeutic management of patients with B cell NHL. While detection of clonal Ig rearrangements is widely used to distinguish reactive from malignant lymphoproliferative disorders, molecular informativity is variable. The relative roles of cytogenetic, molecular and immunological techniques in the detection of genetic abnormalities and their protein products varies with the clinical situation. Consequently, the role of molecular analysis relative to morphological classification is evolving. Integrated diagnostic services are best equipped to cope with these changes. Recent evidence that large scale gene expression profiling allows improved prognostic stratification of diffuse large cell lymphoma suggests that the choice of diagnostic techniques will continue to change significantly and rapidly.

In Section II, Dr. Willerford reviews current understanding of the mechanisms involved in immunoglobulin (Ig) gene rearrangement during B lymphoid development and the way in which these processes may contribute to Ig-locus chromosome translocations in lymphoma. Recent insights into the regulation of Ig gene diversification indicate that genetic plasticity in B lymphocytes is much greater than previously suspected. Physiological genomic instability, which may include isotype switching, recombination revision and somatic mutation, occurs in germinal centers in the context of immune responses and may explain longstanding clinical observations that link immunity and lymphoid neoplasia. Data from murine models and human disorders predisposing to NHL have been used to illustrate these issues.

In Section III, Dr. Morris reviews the characteristics and consequences of deregulation of novel “proto-oncogenes” involved in B cell NHL, including PAX5 (chromosome 9p 13), BCL8 (15q11-q13), BCL9, MUC1, FcγRIIB and other 1q21-q22 genes and BCL10 (1p22). The AP12-MLT/MALT1 [t(11;18)(q21;q21)] fusion transcript is also described.

Non-Hodgkin's Lymphoma: Molecular Features of B Cell Lymphoma

The rapid increase in the incidence of the B cell non-Hodgkin's lymphomas (NHL) and improved understanding of the mechanisms involved in their development renders timely a review of the theoretical and practical aspects of molecular abnormalities in B cell NHL.

In Section I, Dr. Macintyre addresses the practical aspects of the use of molecular techniques for the diagnosis and therapeutic management of patients with B cell NHL. While detection of clonal Ig rearrangements is widely used to distinguish reactive from malignant lymphoproliferative disorders, molecular informativity is variable. The relative roles of cytogenetic, molecular and immunological techniques in the detection of genetic abnormalities and their protein products varies with the clinical situation. Consequently, the role of molecular analysis relative to morphological classification is evolving. Integrated diagnostic services are best equipped to cope with these changes. Recent evidence that large scale gene expression profiling allows improved prognostic stratification of diffuse large cell lymphoma suggests that the choice of diagnostic techniques will continue to change significantly and rapidly.

In Section II, Dr. Willerford reviews current understanding of the mechanisms involved in immunoglobulin (Ig) gene rearrangement during B lymphoid development and the way in which these processes may contribute to Ig-locus chromosome translocations in lymphoma. Recent insights into the regulation of Ig gene diversification indicate that genetic plasticity in B lymphocytes is much greater than previously suspected. Physiological genomic instability, which may include isotype switching, recombination revision and somatic mutation, occurs in germinal centers in the context of immune responses and may explain longstanding clinical observations that link immunity and lymphoid neoplasia. Data from murine models and human disorders predisposing to NHL have been used to illustrate these issues.

In Section III, Dr. Morris reviews the characteristics and consequences of deregulation of novel “proto-oncogenes” involved in B cell NHL, including PAX5 (chromosome 9p 13), BCL8 (15q11-q13), BCL9, MUC1, FcγRIIB and other 1q21-q22 genes and BCL10 (1p22). The AP12-MLT/MALT1 [t(11;18)(q21;q21)] fusion transcript is also described.