Biclonality of gastric lymphomas

The pathogenesis and clonal evolution of gastric diffuse large B-cell lymphoma (DLBCL) and its relationship to extranodal marginal zone B-cell lymphoma (MZBL), mucosa-associated lymphoid tissue (MALT) type, are still controversial. The aim of this study was to establish the clonality of morphologically distinct areas of gastric lymphomas as well as their genetic relationship to each other. Six gastric lymphomas, consisting of two MZBL, MALT type, two DLBCL, and two "composite" lymphomas were subjected to laser capture microdissection and subsequent PCR-based amplification of the immunoglobulin heavy chain gene. One DLBCL showed a biclonal pattern of rearranged immunoglobulin heavy chain (IgH) genes of two different areas without evidence of a common origin. Two composite DLBCL with areas of extranodal MZBL, MALT type, were also biclonal and displayed different IgH gene rearrangements in the small-cell and in the large-cell components, respectively. Sequencing of the CDR3 region revealed unique VH-N-D and D-N-JH junctions, thus corroborating the presence of two genuinely distinct tumor clones in each of these three cases. In contrast, the remaining three gastric lymphomas (one DLBCL and two MZBL, MALT type) showed IgH gene rearrangements in which CDR3 regions were identical in the different tumor areas. Our results suggest that gastric DLBCL may be composed of more than one tumor cell clone. Further, DLBCL may not necessarily evolve by transformation of a low-grade lymphoma, but may also originate de novo. An ongoing emergence of new tumor clones may considerably hamper molecular diagnosis and follow-up of gastric DLBCL.     

Lymph nodes in gastric B-cell lymphoma: pattern of involvement and early histological changes

AIMS: This study aims to analyse the histological pattern of nodal involvement in gastric B-cell lymphoma and to detect early involvement of the lymph nodes. METHODS AND RESULTS: Histological findings of 37 resected primary gastric lymphomas with 1313 regional lymph nodes were analysed. The primary tumour was classified into four groups: MALT lymphoma, MALT lymphoma with a minor large B-cell lymphoma (<20%), large B-cell lymphoma with MALT lymphoma, and large B-cell lymphoma without MALT lymphoma. Histological patterns of nodal involvement were divided into sinusoidal, subsinusoidal/marginal, follicular, and diffuse patterns. Semi-nested polymerase chain reaction (PCR) analysis for IgH gene rearrangement was performed. Nodal involvement was found in 2/13 (15%) MALT lymphomas, 5/6 (83%) MALT lymphomas with a minor large B-cell lymphoma, 9/12 (75%) large B-cell lymphomas with MALT lymphoma, and 6/6 (100%) large B-cell lymphomas without MALT lymphoma. The MALT lymphoma and MALT lymphoma with a minor large B-cell lymphoma showed a predominantly sinusoidal and subsinusoidal pattern, whereas diffuse pattern predominated in large B-cell lymphomas without MALT lymphoma and large B-cell lymphomas with MALT lymphoma. The follicular pattern was least common, being observed in 10.2% of large B-cell lymphomas without MALT lymphoma and large B-cell lymphomas with MALT lymphoma. Sinusoidal obliteration with permeation of small monocytoid cells into subsinusoidal zone is a characteristic finding suggesting early nodal involvement of MALT lymphoma. CONCLUSIONS: Histological patterns of nodal involvement in gastric B-cell lymphoma vary according to the histological grade. Immunostaining for CD20 with or without PCR analysis for IgH gene rearrangement would be a useful ancillary method to confirm lymphomatous involvement.     

胃MALT淋巴瘤中API2-MALT1的检测及其临床病理意义

目的 检测t(11；18)所致API2-MALT1融合转录本的发生率，探讨其对胃MALT淋巴瘤(extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue，MALT lymphoma)病理诊断的意义。方法 收集原发性胃MALT淋巴瘤手术切除、石蜡包埋标本26例为实验组；含MALT成分的胃弥漫性大B细胞淋巴瘤(diffuse large B-cell lymphoma，DL-BCL)和单纯的胃DLBCL手术切除、石蜡包埋标本各10例及慢性胃炎活检石蜡包埋标本10例作为对照组。采用半嵌套式PCR检测B细胞IgH基因重排；采用RT-PCR检测API2-MALT1融合转录本，并通过形态学、免疫组化及分子生物学方法的比较，研究API2-MALT1融合转录本的检测在MALT淋巴瘤诊断中的意义。结果 IgH基因重排的阳性率在胃MALT淋巴瘤中为76.9％(20/26)，在含MALT成分的胃DLBCL中为100％(10/10)，在胃DLBCL中为80％(8/10)，在慢性胃炎中为0(0/10)；API2-MALT1融合转录本在胃MALT淋巴瘤中的检出率为19.2％(5/26)，在含MALT成分的胃DLBCL、胃DL-BCL和胃炎中均未检出。结论API2-MALT1是胃MALT淋巴瘤特异性的诊断指标，但其阳性率相对较低，通过与形态学、免疫组化及B细胞IgH基因重排检测的结合，对胃MALT淋巴瘤的诊断和鉴别诊断具有重要价值。     

Increased sensitivity of B-cell clonality analysis in formalin-fixed and paraffin-embedded B-cell lymphoma samples using an enzyme blend with both 5′→3′ DNA polymerase and 3′→5′ exonuclease activity

Polymerase chain reaction (PCR)-based detection of immunoglobulin heavy chain (IgH) gene rearrangement for determination of B-cell clonality needs to be simple but optimally sensitive. Efficient IgH PCR analysis can be hampered by sequence variability in the template DNA, despite of the use of degenerative primers. To improve sensitivity of the B-cell clonality analysis in formalin-fixed and paraffin-embedded (FFPE) tissues, we have performed framework three-area (FR3)/joining gene (JH) IgH PCR utilizing an enzyme blend (rTth DNA Polymerase, XL) providing both 53 polymerase and 35 exonuclease activities. The DNA samples were extracted from FFPE biopsies of 43 mature B-cell lymphoma cases of so-called germinal center and post-germinal center origin, including 6 nodal follicular lymphomas (FL), 15 gastric mucosa-associated lymphoid tissue (MALT) lymphomas, and 22 gastric diffuse large B-cell lymphomas (DLBCL). Of the cases, 31 (17 DLBCL and 14 MALT lymphoma) represented small endoscopic biopsies. Serial dilutions of target DNA were applied to avoid inconsistent bands that may be seen when the input amount of template is too low, which can be the case when DNA is extracted from FFPE endoscopic gastric biopsies. Using conventional Taq polymerase, consistent monoclonal product was found in 53% (23/43) of the cases (FL: 67%; MALT lymphoma: 47%; DLBCL: 55%). The rTth polymerase showed reproducible monoclonal pattern in 72% (31/43) of the cases (FL: 67%; MALT lymphoma: 73%; DLBCL: 73%); the sensitivity is compatible with one that can be detected with conventional FR3/JH PCR in fresh/frozen tissues. In conclusion, the rTth DNA polymerase greatly improves sensitivity of FR3/JH PCR in FFPE biopsies of mature B-cell lymphomas, most probably by increasing the primer matches during PCR amplification.     

Detection of monoclonality of gastric MALT lymphoma using PCR method and its clinicopathological application

Twenty cases of H. pylori-related gastric lymphoproliferative disorders including 12 cases of MALT lymphoma (Grade 5 after Wotherspoon, et al), 6 of suspicious of MALT lymphoma (Grade 4), and 2 of active chronic gastritis (Grade 3) were studied. Using the nested PCR method, paraffin-embedded gastric biopsy specimens of these 20 cases were investigated whether or not monoclonal IgH rearrangement could be demonstrated in infiltrating lymphoid cells. Monoclonal IgH rearrangement was recognized in 6 of 12 MALT lymphomas, but in other 14 cases including 6 of MALT lymphomas the monoclonality was not recognized. The result showed the sensitivity was 50% and the specificity was 100% with this method. Follow-up study after eradication of H. pylori was performed on 6 cases of MALT lymphoma which had showed the monoclonality before, using the same method. The monoclonality disappeared in 5 of 6 and histology showed a complete remission. In the remaining one case the monoclonality was yet demonstrated and lymphoma cells were histologically recognized. Thus, this method is very useful to assess not only the histological diagnosis of MALT lymphoma but also the effectiveness after treatment.     

Mutational analysis of the 5' noncoding region of the bcl-6 gene in primary gastric lymphomas.

Bcl-6 mRNA and protein are frequently expressed in the transformed counterparts of the germinal center B-cells, diffuse large B-cell lymphoma and follicular lymphoma, irrespective of the gene rearrangements. Most of the primary gastric lymphomas are thought to be of mucosa-associated lymphoid tissue (MALT) origin, and neither bcl-6 gene rearrangement nor protein expression is found in low-grade gastric lymphomas of the MALT type as in normal marginal zone cells. However, bcl-6 protein expression was identified in high-grade gastric lymphomas, suggesting its role in high-grade transformation. In this study, polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis for bcl-6 primer was performed in order to ascertain the molecular mechanisms of bcl-6 protein expression in primary gastric lymphomas. A total 31 cases of gastric lymphoma were classified into low-grade gastric lymphomas of MALT type (n = 13), high-grade gastric lymphomas of MALT type (n = 6) and gastric diffuse large B-cell lymphomas (n = 12). Bcl-6 mutations were observed in 11 of 13 (84.6%) low-grade gastric lymphomas of the MALT type and in 8 of 12 (66.7%) diffuse large B-cell gastric lymphomas. In 6 cases of the high-grade gastric lymphomas of the MALT type, both the low- and high-grade components demonstrated the same frequency (3/6, 50%) of mutations. The tissue obtained from the marginal zone of Peyer's patch by microdissection technique revealed no bcl-6 mutations by the PCR-SSCP analysis. These findings suggest that the acquisition process of bcl-6 mutations by the marginal zone cells may be involved in the lymphomagenesis of the stomach, but our data does not explain the reason why bcl-6 protein is expressed only in high-grade gastric lymphomas.     

High incidence of B-cell monoclonality in follicular gastritis: a possible association between follicular gastritis and MALT lymphoma

Many studies have indicated a close association between gastric mucosa-associated lymphoid tissue (MALT) lymphoma and Helicobacter pylori ( Hp) infection. Follicular gastritis (FG), a rare type of gastritis, is also closely associated with Hp infection and histologically similar to MALT lymphoma. However, there are few studies investigating the relationship between FG and MALT lymphoma. To clarify the issue, we examined the B-cell monoclonality in FG by immunoglobulin heavy chain (IgH) gene rearrangement. Seventy FG patients (all Hp-positive, 23 males and 47 females, median age 33 yr) were investigated; 70 age-and gender-matched non-FG Hp-positive controls and 24 non-FG Hp-negative controls were also examined. Two gastric biopsies, one from the antrum and one from the corpus, were obtained from each patient. DNA was extracted from formalin-fixed, paraffin-embedded biopsy specimens. IgH gene rearrangement was examined by semi-nested polymerase chain reaction (PCR). In the antral mucosa, monoclonal B-cell populations were detected in 19 (32%) of 60 FG, in 6 (10%) of 60 Hp-positive controls, and in none of 20 Hp-negative controls. In the corporal mucosa, monoclonal B-cell populations were detected in 14 (30%) of 47 FG, in 6 (11%) of 54 Hp-positive controls, and in none of 20 Hp-negative controls. The incidence of monoclonal B-cell populations in the FG patients was higher than in both Hp-positive and Hp-negative controls ( P<0.05). The monoclonal B-cell populations disappeared after successful Hp eradication in 8 of 8 FG patients examined. These data suggest that FG may be strongly associated with MALT lymphoma, and that Hp eradication therapy may be indicated in FG.     

Primary gastric lymphomas: Morphologic, immunohistochemical and immunogenetic analyses

Morphologic, lmmunohistochemical and lmmunogenetic studies were performed on 28 cases of primary gastric lymphoma from fresh frozen tissue. Eight cases were diagnosed as diffuse large B-cell lymphoma, four as follicular center lymphoma (follicular), five as mucosa-associated lymphoid tissue (MALT) lymphoma, three as plasmacytoma, and three as T-cell lymphoma, two as mantle cell lymphoma, one as follicular center lymphoma (diffuse, predominantly small cell), and one as lymphoplasmacytoid lymphoma, and one as Hodgkin's disease.
From lmmunohistochemical studies, four types of morphologically similar low-grade lymphomas can be differentiated by a combination of various monoclonal antibodies. Cases of diffuse large B-cell lymphoma may have a germinal center origin. We observed lympho-epithelial lesions in cases of non-MALT lymphomas. We therefore consider that the current diagnostic criterion for MALT lymphoma may not always be valid.
Except for cases of T-cell lymphoma and Hodgkin's disease, 17 out of 22 cases revealed clonal rearrangement bands of the JH gene. In situ hybridization (ISH) and polymerase chain reaction (PCR) studies revealed the presence of Epstein-Barr (EB) virus genomes in two and three cases, respectively. Epstein-Barr virus may play a role in lympho-magenesis, although on relatively rare occasions.     

FAS (CD95) mutations are rare in gastric MALT lymphoma but occur more frequently in primary gastric diffuse large B-cell lymphoma

A loss of FAS (CD95) function has been proposed to constitute an important step in early mucosa-associated lymphoid tissue (MALT) lymphoma development and FAS mutations have been recognized in malignant lymphomas, in particular at extranodal sites. Since primary gastric lymphomas frequently exhibit resistance to FAS-mediated apoptosis, we investigated whether FAS is mutated in 18 gastric MALT lymphomas and 28 diffuse large B-cell lymphomas (DLBCL). We detected seven mutations in five lymphomas, one MALT lymphoma and four DLBCL; two DLBCL had two mutations. The MALT lymphoma exhibited a point mutation in the splice donor region of intron 3. Three DLBCL had missense mutations in exon 2, which encodes a signal peptide and a portion of the extracellular FAS ligand-binding domain. One DLBCL carried a point mutation in the splice donor region of intron 8, which would result in exon skipping. Two DLBCL harbored a missense mutation in exon 9, which encodes the intracellular death domain. The two death domain mutations inhibited FAS ligand-induced apoptosis in a dominant-negative mode, when transiently expressed in human T47D breast carcinoma and Jurkat T cells. A signal peptide and an extracellular domain mutation, however, failed to inhibit apoptosis in these transfection assays. They are likely to reduce apoptosis in lymphoma cells solely by a loss of function. In summary, our data show that FAS mutations are rare in primary gastric MALT lymphomas (5.6%) but occur in a subset of primary gastric DLBCL (14.3%) and suggest that these mutations contribute to the pathogenesis of gastric lymphomas by rendering lymphocytes resistant to apoptosis.     

Oligoclonality of a "composite" gastric diffuse large B-cell lymphoma with areas of marginal zone B-cell lymphoma of the mucosa-associated lymphoid tissue type

We analyzed a case of oligoclonal Helicobacter pylori-associated, primary gastric diffuse large B-cell lymphoma (DLBCL) with areas of extranodal marginal zone B-cell lymphoma (MZBL) of mucosa-associated lymphoid tissue (MALT) type in a 61-year-old male patient. The patient had two separate tumors, in the corpus and in the antrum, each showing two morphologically distinct components (DLBCL and MZBL of MALT type). To determine the clonal relationship between the large- and small-cell components, we microdissected four samples from morphologically distinct tumor components at both tumor sites. PCR analysis revealed rearranged immunoglobulin heavy chain (IgH) genes of different sizes in three of the four microdissected samples. Cloning and sequencing of the PCR products displayed different IgH gene rearrangements in the two small cell components of the antrum and the corpus. A third genuinely differently rearranged IgH gene was found in the large-cell components of both antrum and corpus. Our results suggest that in primary gastric DLBCL with areas of MZBL of MALT type, the small-cell component may comprise more than one tumor clone. Furthermore, the large-cell component may evolve independently from coexisting MZBL.     

儿童散发性伯基特淋巴瘤的分子遗传学特征分析

目的 研究儿童散发性伯基特淋巴瘤(BL)的分子遗传学特征及其诊断和鉴别诊断.方法 对64例儿童BL和6例儿童弥漫性大B细胞淋巴瘤(DLBCL)进行免疫组织化学染色(SP法)和荧光原位杂交(FISH)技术检测c-myc、bcl-2、bcl-6、IgH、myc/lgH及bcl-2/IgH基因重排的情况.根据细胞起源分类分为生发中心组(GC组)、生发中心晚期组(late-GC组)、生发中心后组(post-GC组).结果 BL表达CD20(64例)、CD10(63例)、bcl-6(62例)、MUM1(15例)、bcl-2(0例).GC组49例(76.6%)、late-GC组14例(21.9%)、post-GC组1例(1.6%).c-myc基因断裂54例(93.1%);IgH基因断裂48例(82.8%);c-myc与IgH基因同时断裂并myc/IgH基因易位46例(85.2%);c-myc基因断裂、IgH和myc/IgH基因正常4例(7.4%);c-myc、IgH和myc/IgH基因均正常4例(7.4%);bcl-2基因正常61例(100%);bcl-6基因正常59例,1例断裂并扩增具有BL的病理形态和免疫表型特征,同时具有c-myc基因断裂,将病理诊断修改为介于DLBCL和BL之间的未分类的B细胞淋巴瘤(DLBCL/BL).6例DLBCL中c-myc基因断裂2例;2例bcl-6基因扩增,其中1例伴c-myc基因断裂;无bcl-2/IgH基因重排.结论 儿童散发性BL大多数来源于生发中心B细胞,c-myc基因的断裂是其主要分子遗传学改变.应用FISH进行多基因的检测,有助于提高儿童BL的诊断和鉴别诊断水平.     

Monoclonality in Helicobacter pylori-positive gastric biopsies: an early detection of mucosa-associated lymphoid tissue lymphoma

Mucosa-associated lymphoid tissue (MALT) is not present in healthy gastric mucosa, but it can develop in sites of long-persisting inflammation and is connected with the development of MALT lymphoma. A monoclonal lymphocyte population is one of the characteristics of such lymphomas. In this study we analyzed gastric biopsies (formalin fixed and paraffin embedded or frozen) in 93 patients with dyspepsia accompanied by Helicobacter pylori infection. We applied PCR and single-cell immunocytochemistry to detect the clonality of the gastric B-cell population. Immunocytochemistry performed on 33 frozen biopsies showed two samples with monoclonal pattern. PCR analysis of immunoglobulin heavy-chain (IgH) gene rearrangements revealed two monoclonal populations out of 161 biopsies from 60 patients. We conclude that PCR analysis was the most sensitive method, which gave us insight into the nature of the earliest stage of MALT lymphoma in gastric biopsies.     

胃肠道黏膜相关边缘区B细胞淋巴瘤和弥漫性大B细胞淋巴瘤中API2-MALT1融合基因表达的差异

目的 比较t(11;18)(q21;q21)/API2-MALX1融合基因在胃肠道黏膜相关边缘区B细胞淋巴瘤(MALN淋巴瘤)和弥漫性大B细胞淋巴瘤(DLBCL)中的发生情况,探讨t(11;18)(q21;q21)与胃肠道MALT淋巴瘤和DLBCL间演进的关系.方法 收集57例胃肠道MALT淋巴瘤(包括38例胃和19例肠),32例胃肠道DLBCL(包括28例胃和4例肠)和7例胃DLBCL同时合并MALT淋巴瘤成分,用荧光原位杂交(FISH)检测API2-MALT1融合基因.使用的探针包括API2-MALT1双色融合易位探针和MALT1双色分离重排探针.结果 在MALT淋巴瘤中有21.1%(12/57,包括10例胃和2例肠)发现API2-MALT1融合基因,而在32例DLBCL和7例DLBCL与MALT淋巴瘤混合的病例中均未检测出API2-MALT1融合基因.两组经统计学比较差异有统计学意义(X~2=9.383,P=0.001).结论 API2-MALT1融合基因是MALT淋巴瘤中特异的遗传学异常,而不见于DLBCL或DLBCL与MAIX淋巴瘤共存的病例中,提示至少在胃肠道API2-MALT1阳性的MALT淋巴瘤一般不会发生大细胞转化,而胃肠道DLBCL可能为原发或由t(11;18)阴性的部分MALT淋巴瘤转化而来.     

Micronodular thymoma: an epithelial tumour with abnormal chemokine expression setting the stage for lymphoma development

The aetiology of primary B-cell lymphomas of the thymus is enigmatic. Although thymic follicular lymphoid hyperplasia (TFH) is commonly associated with myasthenia gravis (MG), lymphoma is not a complication of this condition. The present paper reports a high frequency of monoclonal B-cell populations (6 of 18 cases; 33%) in micronodular thymoma (MNT), a peculiar thymic epithelial neoplasm with a B-cell-rich stroma, while B cells were consistently polyclonal in TFH (25 cases) and other types of thymomas (15 cases) (p < 0.001). An intratumoural lymphoma could be identified in three of the six monoclonal MNTs. Sequencing of the monoclonal IgH chain revealed partially overlapping VDJ gene usage in MNT and thymic mucosa-associated lymphoid tissue (MALT) lymphomas. The neoplastic epithelium of MNTs, but not of TFH and other types of thymoma, expressed high levels of dendritic cell, T-cell, and B-cell chemoattractants, such as CCL18, CCR6, and CCL20. It is concluded that abnormal chemokine expression in an epithelial tumour, MNT, can promote the recruitment of MALT, the emergence of monoclonal B cells, and, eventually, the subsequent development of mediastinal lymphomas. More generally, the concept that expression of a 'high-risk' spectrum of chemokines due to local or genetic factors may interfere with B-cell homeostasis and may contribute to MALT lymphoma development in chronic inflammatory states is proposed.     

Immunohistochemistry and gene rearrangement studies in the diagnosis of malignant lymphomas: a comparison of 152 cases.

One hundred fifty-two cases (155 specimens) of lymphoproliferative disorders were studied by immunohistochemistry and gene rearrangement analysis. Ninety-five of 96 B-cell lymphomas (99%) showed genotypic B-cell monoclonality. Of these, five cases had rearranged T-cell receptor (TCR) beta chain gene in addition to immunoglobulin heavy chain (IgH) and kappa light chain (Ig-K), one case had rearranged IgH and TCR-gamma chain but not Ig-K or TCR-beta, and two cases had only Ig-K rearrangement. One exceptional case in the B-cell lymphoma group had unrearranged, germline genotypes. In contrast, only 10 of 19 (53%) phenotypic T-cell lymphomas had rearranged TCR-beta, eight with concurrent TCR-gamma rearrangement. Of the remaining nine cases, six had germline configuration, two had rearranged Ig-K only, and one had both IgH and Ig-K rearrangement. This last case was reclassified as T-cell predominant, B-cell lymphoma. Thirteen of 16 cases of Hodgkin's disease had germline configuration; three cases had rearranged IgH and Ig-K, of which two were lymphocyte predominant with light chain monoclonality and one was a recurrence. Among 21 reactive lesions, 17 had germline configuration and four had rearranged IgH and Ig-K genes. Of these four cases, two were orbital lesions, one was a partially involved lymph node, and one developed a nodular lymphoma 9 months later. Our results indicate that almost all B-cell lymphomas have IgH and/or Ig-K rearrangement. In contrast, peripheral T-cell lymphomas have greater genotypic heterogeneity, and germline patterns for TCR genes are not uncommon. Reactive lesions and Hodgkin's disease tend to retain germline configuration, and any exception is often associated with an unusual clinical setting and/or histology. Genotypic analysis is thus most indicated in B-cell lymphomas with equivocal immunohistochemistry findings, T-cell lymphomas, and atypical cases of Hodgkin's disease and reactive lesions.     

Gastric T-cell lymphoma with cytotoxic phenotype

Primary gastric lymphoma usually originates from B cells of mucosa-associated lymphoid tissue (MALT) infected with Helicobacter pylori. When T-cell lymphomas develop in the stomach, they usually occur in association with infection by human T-lymphotropic virus type 1 and gastric involvement of adult T-cell leukemia. Reported herein is a unique and informative case of gastric peripheral T-cell lymphoma with a cytotoxic phenotype that histologically mimicked, and had to be carefully distinguished from, MALT-type B-cell lymphoma. The patient, a 73-year-old woman, underwent a gastric endoscopy examination, and the histological findings suggested MALT-type gastric lymphoma. Analysis of the immunoglobulin heavy chain (IgH) gene and T cell receptor gamma (TCRgamma) gene revealed monoclonal rearrangement of the TCRgamma gene. The tumor cells exhibited mild atypia and immunoreactivity with anti-CD3, anti-CD8, anti-T-cell intracellular antigen-1, antigranzyme B and antiperforin antibodies, but not with anti-CD20, anti-CD10, and anti-CD79a antibodies. The case was finally diagnosed as gastric T-cell lymphoma with cytotoxic phenotype, and this was confirmed after surgical resection. In cases such as this, small biopsy specimens from the stomach should be examined carefully for low grade B-cell-type malignant lymphoma (MALT lymphoma), because sometimes the proliferating B cells can hide the truly malignant T cells, and rearrangement analysis is useful for diagnosing T-cell malignancy.     

Chromosomal instability in gastric mucosa-associated lymphoid tissue lymphomas: a fluorescent in situ hybridization study using a tissue microarray approach

Extranodal marginal zone B-cell lymphomas (mucosa-associated lymphoid tissue [MALT] lymphomas) of the gastrointestinal tract have been known to have characteristic chromosomal aberrations including trisomies of chromosomes 3, 12, and 18. However, knowledge of the clinical significance of cytogenetic changes in MALT lymphomas is still limited. In the present study, the frequency of the numeric and structural aberrations of the chromosomes 1, 3, 12, 18 and X and of the MALT1 gene as well as their potential clinical significance were analyzed by using fluorescent in situ hybridization on a tissue microarray containing 257 tissue samples from 203 cases of surgically resected primary gastric lymphomas including 115 cases of MALT lymphomas, 88 cases of diffuse large B-cell lymphomas (DLBCLs, 75 with an associated MALT lymphoma, so-called ex-MALT DLBCL, and 13 de novo), and 54 controls cases of Helicobacter pylori-associated chronic gastritis. Clinical follow-up information was available in 137 cases. Trisomies 1, 3, 12, and 18 were detected in 3.3%, 44.4%, 12.3%, and 19.2% of MALT lymphomas and in 11.1%, 42.2%, 26.5%, and 22.0% of ex-MALT DLBCLs, respectively. In addition, we found gains of the X chromosome in 36.4% of MALT lymphomas, in 34.5% of ex-MALT DLBCLs, and in 36.4% of de novo DLBCLs. Structural and/or numeric abnormalities of the MALT1 gene were observed in 37.0% of MALT lymphomas and in 22.2% of ex-MALT DLBCLs. In de novo DLBCL, trisomies for chromosomes 3, 12, 18, and X were found in 42.9%, 10.0%, 11.1%, and 36.4%, respectively, whereas alterations of MALT1 (namely, translocations) were found in 20.0% of the cases. An unexpected high and previously unreported gain of chromosome X in gastric MALT lymphomas was found. This tumor appears, therefore, to be a genetically unstable neoplasia. Our results point out that t(11;18) and aneuploidy may be both involved in lymphomagenesis and that at least a subset of MALT lymphomas may progress toward high-grade neoplasia.     

MALT lymphoma involving the kidney: a report of 10 cases and review of the literature

Extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) can arise at any anatomic site, but involvement of the kidney is rare. We describe 10 cases of kidney MALT lymphoma, including 6 localized cases. No predisposing inflammatory conditions were identified, with the possible exception of coexistent renal Actinomyces infection in 1 case. We performed fluorescence in situ hybridization (FISH) using a malt1 break-apart probe in 7 cases. A malt1 gene rearrangement was identified in 1 case (14%). This case was further assessed by FISH using an IgH breakapart probe that showed IgH gene rearrangement. These results are suggestive of the t(14;18) involving malt1 and IgH. Immunostaining for NF-kappaB p65 showed nuclear positivity, consistent with NF-kappaB activation, in 3 of 5 cases assessed. Our results indicate that kidney MALT lymphomas share similarities with MALT lymphomas arising at other sites in that MALT lymphoma-associated translocations and NF-kappaB activation occur in a subset of cases.     

The role of Helicobacter pylori in primary gastric MALT lymphoma

AIMS: Helicobacter pylori has been claimed to be an important aetiological factor which raises the risk of mucosa-associated tissue lymphoid (MALT) lymphoma. However, some studies on gastric MALT lymphoma revealed a low rate of H. pylori infection suggesting that not all gastric lymphomas are related to H. pylori infection. The aim of this study was to verify the H. pylori infection frequency in a series of patients with primary gastric MALT lymphomas and to examine the relationship between H. pylori and the pathological features of those lymphomas. METHODS AND RESULTS: Thirty-one cases of resected gastric lymphoma were analysed: 10 cases (32%) were low-grade MALT lymphomas and 21 cases (68%) were high-grade MALT lymphomas. Helicobacter pylori was found in only 18 of 31 (58%) cases. Helicobacter pylori infection was significantly correlated with the grade and depth of invasion of MALT lymphoma since 63% of superficial low-grade MALT lymphomas were positive for H. pylori compared with 38% of advanced high-grade MALT lymphomas (P = 0.02). CONCLUSION: We confirmed the relationship between H. pylori infection and a subset of gastric MALT lymphoma. Our results also showed that not all low- and high-grade gastric MALT lymphomas are H. pylori-dependent. This suggests that H. pylori infection may play a promoter role in the development of MALT lymphoma, but its presence is not mandatory for the progression of the lymphoma in view of its low frequency in advanced high-grade MALT lymphoma.     

眼附属器淋巴组织增生性病变的临床病理和分子遗传学特征及其意义

目的 分析眼附属器淋巴组织增生性病变的临床病理特点,探讨其分子遗传学特征及其意义.方法 收集1995-2007年37例眼附属器淋巴组织增生性病变石蜡组织标本(其中5例为反应性增生性病变,32例为淋巴瘤),依据2001年WHO肿瘤分类标准对32例淋巴瘤标本重新诊断分类.采用IgH、MALT1、bcl-6、c-Mye、bcl-2、CCND1、bcl-10、FOXP1双色分离重排探针、IgH/bcl-2双色融合易位探针和18号染色体着丝粒探针,利用间期荧光原位杂交(FISH)的方法 检测眼附属器淋巴组织增生性病变的分子遗传学特点.结果 32例淋巴瘤均为非霍奇金B细胞淋巴瘤.其中,黏膜相关淋巴组织结外边缘区B细胞淋巴瘤(MALT)淋巴瘤28例(87.5%),滤泡性淋巴瘤2例,弥漫性大B细胞淋巴瘤2例.60.7%(17/28)的眼附属器MALT淋巴瘤携带分子遗传学异常.其中,IgH基因断裂1例,但未找到与其发生相互易位的伙伴基因;基因3拷贝者16例,其中MALT1基因、bcl-6基因和c-Myc基因3拷贝的发生率分别为25%(7/28)、43%(12/28)和7%(2/28).16例基因3拷贝病例中,两种基因3拷贝合并存在者5例,其中bcl-6基因合并MALT1基因3拷贝者4例,bcl-6基因合并c-Myc基因3拷贝者1例.进一步研究显示,MALT1基因3拷贝者均存在18号染色体三体.2例滤泡性淋巴瘤都携带t(14;18)(q32;q21)/IgH-bcl-2.2例弥漫性大B细胞淋巴瘤均存在遗传学异常,1例表现为bcl-6基因3拷贝合并18号染色体三体,另1例表现为bcl-6基因3拷贝合并IgH和c-Myc基因双断裂.5例反应性淋巴组织增牛性标本均未见分子遗传学异常.结论 MALT淋巴瘤是眼附属器最常见的淋巴瘤类型;间期FISH有助于淋巴组织增生性病变的良恶性鉴别及淋巴瘤的分类;MALTI基因3拷贝者由18号染色体三体所致;18号染色体三体和bcl-6基因3拷贝(可能为3号染色体三体所致)是眼附属器MALT淋巴瘤常见的分子遗传学异常.