Primary mediastinal B-cell lymphoma: update of its clinicopathologic features

Alteration of chromosome arm 6p is characteristic of primary mediastinal B-cell lymphoma, as identified by genome-wide allelotyping

Five cases of primary mediastinal B-cell lymphoma (PMBL) each have been studied with 375 microsatellite markers from all 22 autosomes. Of the 151 genomic alterations among the 1,875 assays, only five were allelic losses. The remainder of the microsatellite alterations consisted of 114 allelic imbalances and 32 instabilities. Microsatellite alterations were found in all cases on chromosomal arms 6p and 9p. These allelic imbalances most likely are indicative of genetic amplification, a finding agreeing well with those of studies using either comparative genomic hybridization or arbitrarily primed polymerase chain reaction, in which amplification of chromosome arm 9p in PMBL has been found. The allelic imbalances on chromosome arm 6p always included marker D6S276 located at 6p21.3-p22.3, where the MHC class I genes reside. These allelic imbalances may be reflective of alterations in the expression of the MHC gene products, characteristic of PMBL. Allelic anomalies close to the MYB gene locus on 6q were detected in two cases and prompted the analysis of MYB rearrangements in a series of 30 lymphomas. One rearrangement was detected in one of 18 cases of PMBL and in none of 10 diffuse, large B-cell lymphomas and two T-cell lymphomas. Our genome-wide microsatellite analysis provides independent confirmation that PMBL is characterized by infrequent chromosomal losses and by frequent genetic alterations involving chromosomal arm 9p. For the first time, chromosomal arm 6p has been identified as a highly frequent target of genetic alterations in this tumor type. Finally, MYB may also be involved occasionally in PMBL pathogenesis.

Gain of chromosome arm 9p is characteristic of primary mediastinal B-cell lymphoma (MBL): comprehensive molecular cytogenetic analysis and presentation of a novel MBL cell line

Primary mediastinal B-cell lymphoma (MBL) is an aggressive Non-Hodgkin's Lymphoma, which has been recognized as a distinct disease entity. We performed a comprehensive molecular cytogenetic study analyzing 43 MBLs. By comparative genomic hybridization (CGH), the most common aberrations were gains of chromosome arms 9p and Xq, which were present in 56% and 40% of cases, respectively. Based on the limited resolution of CGH, this technique may underestimate the real incidence of aberrations. Therefore, we also did an interphase cytogenetic study with eight DNA probes mapping to chromosome regions frequently altered in B-cell lymphomas. With this approach, both 9p and Xq gains were found in more than 70% of cases (75% and 87%, respectively). The findings were compared with results obtained in 308 other B-cell lymphomas. Gains in 9p were identified in only six of the 308 cases, and only one of these lymphomas with 9p gains was not primarily extranodal in origin (P < 10-(20) for CGH data and P < 10-(11) for fluorescence in situ hybridization data). We also present a novel MBL cell line, MedB-1, which carries the genetic aberrations characteristic of this entity.

Genetic alterations in primary mediastinal B-cell lymphoma: an update

Primary mediastinal B-cell lymphoma (PMBL) is a distinct clinical entity among non-Hodgkin's lymphoma. The malignancy has received little attention from a standpoint of basic research due in part to its rarity. However, based on recent studies consistent trends are beginning to emerge regarding the molecular and chromosomal alterations commonly observed in this disease. By both CGH and AP-PCR, genetic gains involving chromosomes 2, 5, 7, 9p, 12, and Xq are among the most frequently observed events. From a molecular standpoint, alterations in the c-myc, p16(INK4) and p53 genes have been observed in up to 30% of cases. This information along with the well-established histological, immunological, and clinical features should convince the few remaining disbelievers that PMBL is a distinct pathological entity among non-Hodgkin's lymphomas.

Salvage therapy for relapsed mediastinal B-cell lymphoma with allogeneic HLA-identical related donor bone marrow transplantation, donor lymphocyte infusion and IDEC-C2B8

Primary B-cell lymphoma of the mediastinum is an aggressive non-Hodgkin's lymphoma with distinct clinicopathologic features. Response rates are between 60-80% following intensive chemotherapy regimens. Poor responders or patients with an early relapse usually do not achieve a prolonged second remission with conventional salvage therapy protocols and therefore qualify for intensive or experimental approaches. Here we describe two patients of same age, gender and stage with primary mediastinal B-cell lymphoma and an early relapse after the first courses of combination chemotherapy and irradiation of the mediastinum. One patient relapsed after a salvage therapy with allogeneic donor-related bone marrow transplantation and donor lymphocyte infusion but responded again with a continuing good partial remission after infusion of the chimeric anti-CD20 antibody IDEC-C2B8. For the other patient an allogeneic bone marrow transplantation was not possible. He finally failed to respond to salvage therapy with IDEC-C2B8 and died of progressive disease. The anti-CD20 antibody IDEC-C2B8 induced a partial remission in a patient with primary mediastinal B-cell lymphoma refractory to other therapeutic approaches, including allogeneic bone marrow transplanatation (alloBMT), donor lymphocyte infusion (DLI) and irradiation. The role of IDEC-C2B8 as a component of salvage regimens appears to be worthy for further evaluation in high-risk patients with primary mediastinal B-cell lymphoma

Treatment and Clinical Management of Primary Mediastinal Large B-Cell Lymphoma With Sclerosis: MACOP-B Regimen and Mediastinal Radiotherapy Monitored by 67Gallium Scan in 50 Patients

To evaluate the efficacy of a combined modality treatment (MACOP-B plus mediastinal radiotherapy) and the advantages of Gallium-67-citrate single-photon emission (67GaSPECT) over computed tomography (CT) for restaging in patients with primary mediastinal large B-cell lymphoma (PMLBCL) with sclerosis. Between 1989 and 1998, 50 previously untreated patients with PMLBCL with sclerosis (70% with bulky mass) were treated with MACOP-B regimen plus mediastinal radiotherapy. The radiologic clinical stage with evaluation of tumor size included CT and 67GaSPECT at diagnosis, after chemotherapy, and after radiotherapy. Forty-three patients (86%) achieved a complete response and 7 were nonresponders to treatment. For the imaging evaluation, only 47 patients were evaluable because 3 had disease progression during chemotherapy. After treatment, 3/5 (60%) patients with positive 67GaSPECT and negative CT scan relapsed, as against 0/21 (0%) with negative 67GaSPECT and CT scan. Twenty-one patients had a positive CT scan: of these, the 4 with positive 67GaSPECT all progressed, whereas there were no relapses among the 17 with negative 67GaSPECT. After radiotherapy, there was a decrease of positive CT (from 33 to 21 cases) and of positive 67GaSPECT (from 31 to 9 cases). Relapse-free survival rate was 93% at 96 months (median 39 months). In patients with PMLBCL with sclerosis, MACOP-B plus radiation therapy is a very useful first-line treatment and radiation therapy may play an important role. As regards restaging, 67GaSPECT should be considered the imaging technique of choice at least in patients who show CT positivity.

Molecular features of primary mediastinal B-cell lymphoma: involvement of p16INK4A, p53 and c-myc

Primary mediastinal B-cell lymphoma (PMBL) shows chromosome 9p anomalies in 50% of cases. Based on reports that p16INK4A gene, located on this chromosomal arm, is frequently altered in aggressive lymphomas, we analysed for alterations of this gene in 27 cases of PMBL, which were part of a series of 32 PMBL cases that have been characterized for alterations in c-myc, p53, N-ras, bcl-1, bcl-2, bcl-6 and for Epstein-Barr virus (EBV) infection. Four cases showed p16INK4A gene anomalies, including three with promoter methylation and one homozygous deletion. Eight PMBLs showed c-myc rearrangements. Three additional cases showed sequence variations in the c-myc P2 promoter, two of which consisted of the same germline variation involving a novel polymorphic XhoI site. Four tumours contained p53 gene mutations and three had clonal EBV infection. One case had a bcl-6 rearrangement. In conclusion, our study shows that p16INK4, c-myc and p53 alterations occur in 15%, 25% and 13% of PMBLs, respectively. EBV monoclonality was found in 9% of cases, whereas no abnormality was detected in bcl-1, bcl-2 and N-ras. Thus, none of the common genetic aberrations seen in other types of non-Hodgkin's lymphomas appears to be stringently involved in the pathogenesis of this unique lymphoma type.