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A study aims to establish a molecular definition of Burkitt's lymphoma and to search for other clinically relevant subgroups of diffuse large-B-cell lymphoma, using transcriptional and genomic profiling. Results show that in mature aggressive B-cell lymphomas without a gene signature for Burkitt's lymphoma, chromosomal breakpoints at the myc locus were associated with an adverse clinical outcome.

BCL2 is a target of somatic hypermutation in t(14;18) positive and also in a small fraction of t(14;18) negative diffuse large B-cell lymphoma (DLBCL), suggesting an aberrant role of somatic hypermutation (ASHM). To elucidate the prevalence of BCL2 mutations in lymphomas other than DLBCL, we Sanger-sequenced the hypermutable region of the BCL2 gene in a panel of 69 mature B-cell lymphomas, including Richter's syndrome DLBCL, marginal-zone lymphomas, post-transplant lymphoproliferative disorders, HIV-associated and common-variable immunodeficiency-associated DLBCL, all known to harbour ASHM-dependent mutations in other genes, as well as 16 t(14,18) negative and 21 t(14;18) positive follicular lymphomas (FLs). We also investigated the pattern of BCL2 mutations in longitudinal samples from 10 FL patients relapsing to FL or transforming to DLBCL (tFL). By direct sequencing, we found clonally represented BCL2 mutations in 2/16 (13%) of t(14;18) negative FLs, 2/16 (13%) HIV-DLBCLs, 1/9 (11%) of Richter's syndrome DLBCL, 1/17 (6%) of post-transplant lymphoproliferative disorders and 1/2 (50%) common-variable immunodeficiency-associated DLBCL. The proportion of mutated cases was significantly lower than in FLs carrying the t(14;18) translocation (15/21, 71%). However, the absence of t(14;18) by FISH or PCR and the molecular features of the mutations strongly suggest that BCL2 represents an additional target of ASHM in these entities. Analysis of the BCL2 mutation pattern in clonally related FL/FL and FL/tFL samples revealed two distinct scenarios of genomic evolution: (i) direct evolution from the antecedent FL clone, with few novel clonal mutations acquired by the tFL major clone, and (ii) evolution from a common mutated long-lived progenitor cell, which subsequently acquired distinct mutations in the FL and in the relapsed or transformed counterpart. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Mantle cell lymphoma (MCL) shares immunophenotypic and karyotypic features with chronic lymphocytic leukaemia. The latter comprises two distinct entities with prognosis dependent upon immunoglobulin heavy chain (IgH) gene mutational status and the presence of 11q deletion. We evaluated the relevance of IgH gene mutational status, IgV gene family usage and presence of 11q deletion in a series of 42 histologically reviewed classical MCL cases to determine the prognostic impact. VH3 was the most common VH family, with VH3-21 being the most frequent individual VH gene. Approximately 30% of the cases had a IgH somatic mutation rate higher than 2%, but was only higher than 4% in <10% of cases. Half of the cases had deletion of chromosome 11q21-telomere (11q21->ter), with two minimal deleted regions, at 11q22.2 and 11q23.2. There was no association between 11q loss and IgH gene somatic mutation rate; the use of VH3-21 gene could be associated with a better prognosis. [ABSTRACT FROM AUTHOR]

Background: Research on prognostically relevant immunohistochemical markers in diffuse large B-cell lymphomas has mostly been performed on retrospectively collected clinical data. This is also true for immunohistochemical classifiers that are thought to reflect the cell-of-origin subclassification of gene expression studies. In order to obtain deeper insight into the heterogeneous prognosis of diffuse large B-cell lymphomas and to validate a previously published immunohistochemical classifier, we analyzed data from a large set of cases from prospective clinical trials with long-term follow-up., Design and Methods: We performed morphological and extensive immunohistochemical analyses in 414 cases of diffuse large B-cell lymphoma from two prospective randomized clinical trials (NHL-B1/B2, Germany). Classification into germinal center and non-germinal center subtypes of B-cell lymphoma was based on the expression pattern of CD10, BCL6, and IRF4. Multivariate analyses were performed adjusting for the factors in the International Prognostic Index., Results: Analyzing 20 different epitopes on tissue microarrays, expression of HLA-DR, presence of CD23(+) follicular dendritic cell meshworks, and monotypic light chain expression emerged as International Prognostic Index-independent markers of superior overall survival. Immunoblastic morphology was found to be related to poor event-free survival. The non-germinal center subtype, according to the three-epitope classifier (CD10, BCL6, and IRF4) did not have prognostic relevance when adjusted for International Prognostic Index factors (relative risk=1.2, p=0.328 for overall survival; and relative risk=1.1, p=0.644 for event-free survival)., Conclusions: The previously reported International Prognostic Index-independent prognostic value of stratification into germinal center/non-germinal center B-cell lymphoma using the expression pattern of CD10, BCL6, and IRF4 was not reproducible in our series. However, other markers and the morphological subtype appear to be of prognostic value.

Background: The aim of this study was to determine the impact of a gain of the MALT1 gene on gene expression and clinical parameters in diffuse large B-cell lymphoma., Design and Methods: We analyzed 116 cases of diffuse large B-cell lymphoma by fluorescence in situ hybridization, array-based comparative genomic hybridization, and transcriptional profiling., Results: A gain of 18q21 including MALT1 was detected in 44 cases (38%) and was accompanied by a gain of BCL2 in 43 cases. All cases with a 18q21/MALT1 gain showed BCL2 protein whereas 79% in the group without a 18q21/MALT1 gain did so (p<0.001). Cases with 18q21/MALT1 gain more frequently showed an activated B-cell-like (ABC) gene expression signature (65%) than a germinal center B-cell-like (GCB) one (23%) (p<0.001). Ninety-eight genes including MALT1, BCL2, and some selected nuclear factor-kappaB target genes were differentially expressed between the two genetic groups of diffuse large B-cell lymphoma. By global testing of each chromosome, we identified 33 genes, all located on chromosome 18q, which were differentially expressed between the two genetic groups independently of the ABC/GCB status. In multivariate analysis, the 18q21/MALT1 status represented an independent negative prognostic factor for overall survival (p=0.03)., Conclusions: In diffuse large B-cell lymphoma, gain of 18q21 including MALT1 is significantly associated with differential expression of genes located on 18q, the ABC gene expression subtype, increased BCL2 gene and protein expression and might indicate an unfavorable prognosis.

Mantle cell lymphoma (MCL) is associated with a very unfavourable clinical course. This is particularly true for mantle cell lymphoma of the blastoid subtype (MCL-b). In order to define prognostic factors, we analysed the impact of immunoglobulin heavy chain variable (IgV H) gene somatic hypermutations on clinical outcome in a series of 21 cases of morphologically, phenotypically, and genotypically well-characterized MCL-b. Testing and estimation were performed using log-rank statistics and displayed on Kaplan-Meier graphs. Thirteen of 21 cases of MCL-b revealed a homology rate of > or = 99% compared to IgV H germ-line sequences in the databases and were scored as non-mutated. Eight of 21 cases (38%) of MCL-b were mutated. In MCL-b the mutation frequency was usually low and the mutation pattern was only rarely antigen-selected, in contrast to a control group of 11 cases with morphologically almost identical, but phenotypically and genotypically clearly distinguishable, diffuse large B cell lymphoma, derived, most likely, from germinal centre B cells. In our series of 21 MCL-b, positive IgV H mutational status, irrespective of varying homology thresholds, had no statistically significant prognostic impact on event-free or overall survival. However, mutated MCL-b tended to present more frequently at an earlier stage and without bone marrow involvement and to show lower rates of relapse and death, resulting in a more favourable clinical outcome., (Copyright 2005 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.)

The diagnostic impact of bone marrow cytology in combination with flow cytometry analysis of aspirate smears and bone marrow histology together with immunohistochemical examination of trephine biopsies was compared in 141 routine cases. Diagnoses achieved by the two methods were concordant in 80.5% of cases. In discordant cases, clinical follow-up data of at least one year confirmed the correctness of cytological and histological diagnoses. For infiltration by malignant disease, both methods were concordant in 86.5% of samples and correlated well for the degree of infiltration (r = 0.64, p <0.001). Overall, regression analysis showed a good correlation for cellularity (r = 0.67) lymphopoiesis (r = 0.75), granulopoiesis (r = 0.73) and megakaryopoiesis (r = 0.65) while erythropoiesis displayed a lower degree of correlation (r = 0.43, all p <0.001). Regression analysis on all immunological data obtained by flow cytometry (FC) and immunohistochemistry (IHC) showed a good overall linear correlation (r = 0.67, p <0.001), but significant differences were found for a few phenotypic markers. Furthermore, the correlation was found to be dependent on IgG subclasses and the fluorochromes used for FC. Thus, analyses with IgG2 antibodies and phycoerythrin (PE) as fluorochrome showed significantly more expression than IHC. In conclusion, cytology and histology, both in association with the respective immunophenotyping, are of equal value in bone marrow diagnostics and should be used in combination. However, in some specific settings, one of the two procedures might be preferable.

The potential benefits of extended rituximab treatment have been investigated in a randomized trial comparing the standard schedule with prolonged treatment in 202 patients with newly diagnosed or refractory/relapsed follicular lymphoma (FL). All patients received standard treatment (rituximab 375 mg/m(2) weekly x 4). In 185 evaluable patients, the overall response rate was 67% in chemotherapy-naive patients and 46% in pretreated cases (P <.01). Patients responding or with stable disease at week 12 (n = 151) were randomized to no further treatment or prolonged rituximab administration (375 mg/m(2) every 2 months for 4 times). At a median follow-up of 35 months, the median event-free survival (EFS) was 12 months in the no further treatment versus 23 months in the prolonged treatment arm (P =.02), the difference being particularly notable in chemotherapy-naive patients (19 vs 36 months; P =.009) and in patients responding to induction treatment (16 vs 36 months; P =.004). The number of t(14;18)-positive cells in peripheral blood (P =.0035) and in bone marrow (P =.0052) at baseline was predictive for clinical response. Circulating normal B lymphocytes and immunoglobulin M (IgM) plasma levels decreased for a significantly longer time after prolonged treatment, but the incidence of adverse events was not increased. In patients with FL, the administration of 4 additional doses of rituximab at 8-week intervals significantly improves the EFS.

The principles of the new WHO classification of haematopoietic and lymphoid tumours are based on those defined in the Revised European American classification of Lymphoid neoplasms (REAL), published by the International Lymphoma Study Group (ILSG) in 1994. Thus, the new WHO classification may be considered an updated version of the REAL classification rather than of the old WHO classification published in 1976. Disease entities are defined on the basis of morphological, phenotypic, genotypic, and clinical data. The relative impact of these characteristics varies among different diseases and there is "no gold standard". Thus, the strict hierarchy among diagnostic criteria, headed by morphology and followed by immunohistochemistry and genetics, has been discontinued. The WHO classification not only encompasses lymphoid tumours but extends to myeloid, mast cell and histiocytic/dendritic cell malignancies. Neoplasms are primarily stratified according to their tumour cell lineage. For each neoplasm a cell of origin is postulated. The classification of lymphoid malignancies recognises three major categories, B-cell neoplasms, T-/NK-cell neoplasms, and Hodgkin lymphomas. B-cell and T-cell lymphomas are further divided into precursor neoplasms and mature neoplasms, the latter being subdivided according to their clinical manifestation into disseminated/leukaemic, extranodal and nodal malignancies. In contrast to previous classifications, the neoplasms are grouped neither according to their histological grade (Kiel classification) nor according to their clinical aggressiveness (International Working Formulation). However, the histological grade is considered a prognostic factor which enters into the description of each disease entity. Hodgkin's disease, now more appropriately termed Hodgkin lymphoma, comprises nodular lymphocyte-predominant Hodgkin lymphoma and classical Hodgkin lymphomas of nodular sclerosis, mixed cellularity, lymphocyte-depleted and lymphocyte-rich subtype. For practical purposes this minireview disregards the description of myeloid, macrophage/histiocytic, dendritic cell and mast cell disorders. Furthermore, the present paper is restricted to those lymphoid tumours that are not already identically described in the REAL classification, in order to focus on what is really new in the WHO classification.