Detection of t(I 1; 18) in MALT-type lymphoma with dual-color fluorescence in situ hybridization and reverse transcriptase-polymerase chain reaction analysis

Recent Advances in the Genetic of MALT Lymphomas

Simple Summary

Mucosa-associated lymphoid tissue (MALT) lymphoma is the most common subtype of marginal zone lymphomas. These B-cell neoplasms may arise from many organs and usually have an indolent behavior. Recurrent chromosomal translocations and cytogenetic alterations are well characterized, some of them being associated to specific sites. Through next-generation sequencing technologies, the mutational landscape of MALT lymphomas has been explored and available data to date show that there are considerable variations in the incidence and spectrum of mutations among MALT lymphoma of different sites. Interestingly, most of these mutations affect several common pathways and some of them are potentially targetable. Gene expression profile and epigenetic studies have also added new information, potentially useful for diagnosis and treatment. This article provides a comprehensive review of the genetic landscape in MALT lymphomas.

Abstract

Mucosa-associated lymphoid tissue (MALT) lymphomas are a diverse group of lymphoid neoplasms with B-cell origin, occurring in adult patients and usually having an indolent clinical behavior. These lymphomas may arise in different anatomic locations, sharing many clinicopathological characteristics, but also having substantial variances in the aetiology and genetic alterations. Chromosomal translocations are recurrent in MALT lymphomas with different prevalence among different sites, being the 4 most common: t(11;18)(q21;q21), t(1;14)(p22;q32), t(14;18)(q32;q21), and t(3;14)(p14.1;q32). Several chromosomal numerical abnormalities have also been described, but probably represent secondary genetic events. The mutational landscape of MALT lymphomas is wide, and the most frequent mutations are: TNFAIP3, CREBBP, KMT2C, TET2, SPEN, KMT2D, LRP1B, PRDM1, EP300, TNFRSF14, NOTCH1/NOTCH2, and B2M, but many other genes may be involved. Similar to chromosomal translocations, certain mutations are enriched in specific lymphoma types. In the same line, variation in immunoglobulin gene usage is recognized among MALT lymphoma of different anatomic locations. In the last decade, several studies have analyzed the role of microRNA, transcriptomics and epigenetic alterations, further improving our knowledge about the pathogenic mechanisms in MALT lymphoma development. All these advances open the possibility of targeted directed treatment and push forward the concept of precision medicine in MALT lymphomas.

A retrospective study of 5-year outcomes of radiotherapy for gastric mucosa-associated lymphoid tissue lymphoma refractory to Helicobacter pylori eradication therapy

BACKGROUND

The favorable response rate of radiotherapy for localized gastric mucosa-associated lymphoid tissue lymphoma refractory to Helicobacter pylori eradication has been demonstrated. However, there are limited data available on the long-term outcomes. The aim of this retrospective study was to evaluate the long-term outcomes of radiotherapy for localized gastric mucosa-associated lymphoid tissue lymphoma refractory to Helicobacter pylori eradication.

METHODS

Thirty-four consecutive patients with localized gastric mucosa-associated lymphoid tissue lymphoma that were refractory to eradication were treated with radiotherapy (a total dose of 30 Gy). The response and adverse events of radiotherapy were retrospectively analyzed as short-term outcomes, and recurrence-free, overall and disease-specific survival rates were calculated as long-term outcomes.

RESULTS

Thirty-three (97.1%) patients achieved complete remission and radiotherapy was well tolerated. One patient underwent emergency gastrectomy due to severe hematemesis. Of the 34 patients during the median follow-up period of 7.5 (1.2-13.0) years, one patient had local recurrence after 8.8 years, one patient underwent surgery for bowel obstruction secondary to small bowel metastasis after 5.1 years and one patient had pulmonary metastasis after 10.9 years. Pathologically, all three recurrences revealed mucosa-associated lymphoid tissue lymphoma without any transformation to high-grade lymphoma. None died of gastric mucosa-associated lymphoid tissue lymphoma. The 5-year recurrence-free survival rate was 97.0%. The 5-year overall survival rates and disease-specific survival rates were 97.0 and 100%, respectively.

CONCLUSIONS

Radiotherapy in patients with localized gastric mucosa-associated lymphoid tissue lymphoma refractory to Helicobacter pylori eradication can achieve excellent overall survival. However, long-term surveillance is necessary to identify late recurrences.

18q21 Rearrangement and trisomy 3 in extranodal B-cell lymphomas: a study using a fluorescent in situ hybridisation technique

t(11;18)(q21;q21) Translocation and trisomy 3 are the most common chromosomal aberrations reported in low-grade mucosa-associated lymphoid tissue (MALT) lymphoma. The current study aims to investigate the frequency of these chromosomal aberrations in a series of 52 extranodal B-cell lymphomas. The tumours were categorised into three histological grades: grade 1 (low-grade lymphoma of MALT type), grade 2 [diffuse large B-cell lymphoma (DLBCL) with MALT component] and grade 3 (DLBCL without MALT component). Fluorescence in situ hybridisation analyses on paraffin tissue sections were performed using a locus-specific probe for the 18q21 region and a centromeric probe for chromosome 3. The 18q21 rearrangement was detected in 9 of 40 (23%) cases, including 7 of 23 (30%) grade-1 and 2 of 11 (18%) grade-3 tumours. Amplification of the 18q21 region was detected in 10 of 40 (25%) cases, and trisomy 3 was detected in 9 of 34 (26%) cases. Amplification of the 18q21 region may be an important alternative pathogenetic pathway in MALT lymphoma and was found almost exclusively in tumours without 18q21 rearrangement. Our study showed that tumours with 18q21 rearrangement and 18q21 amplification develop along two distinct pathways, and the latter was more likely to transform into high-grade tumours upon acquisition of additional genetic alterations, such as trisomy 3. Trisomy 3 was more frequently found in coexistence with 18q21 abnormalities, suggesting that it was more likely to be a secondary aberration.

t(1;14) and t(11;18) in the differential diagnosis of Waldenström's macroglobulinemia

Waldenström's macroglobulinemia is caused by several B-cell proliferative disorders including lymphoplasmacytic lymphoma, marginal zone B-cell lymphoma, B-cell chronic lymphocytic leukemia and multiple myeloma. Differential diagnosis between lymphoplasmacytic lymphoma and extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue is particularly difficult as there is a considerable overlap in histological presentation. We report a case of Waldenström's macroglobulinemia with involvement of the peripheral blood, bone marrow and stomach. Serum chemistry revealed an IgM of 5.4 g/dl, but Bence-Jones protein in urine was negative. Abnormal lymphoid cells were detected in both blood and the bone marrow. Flow cytometry of the bone marrow aspirate showed that majority of cells were CD20(+), CD38(+), expressing immunoglobulin lambda light chain, but CD5(-) and CD10(-). Gastric biopsies revealed infiltration of the gastric mucosa by small lymphoid cells showing plasmacytoid differentiation and occasional Dutcher bodies. Lymphoepithelial lesions and Helicobacter pylori were not seen. Thus, the differential diagnosis between lymphoplasmacytic lymphoma and mucosa-associated lymphoid tissue lymphoma was raised. To resolve this, we performed BCL10 immunohistochemistry and reverse transcriptional polymerase chain reaction (RT-PCR) for the API2-MALT1 fusion transcript of t(11;18)(q21;q21). Both bone marrow and gastric biopsies showed strong BCL10 nuclear staining, similar to that seen in t(1;14)(p22;q32) positive mucosa-associated lymphoid tissue lymphoma, but absence of the API2-MALT1 fusion transcript. To further ascertain whether the detection of t(1;14)(p22;q32) and t(11;18)(q21;q21) can be reliably used for the differential diagnosis between lymphoplasmacytic lymphoma and mucosa-associated lymphoid tissue lymphoma, we screened for these translocations by BCL10 immunohistochemistry in 58 lymphoplasmacytic lymphomas and RT-PCR for t(11;18)(q21;q21) in 40 lymphoplasmacytic lymphomas, respectively. None of the lymphoplasmacytic lymphomas studied harbored these translocations. Thus, detection of t(1;14)(p22;q32) and t(11;18)(q21;q21) is useful in the differential diagnosis between lymphoplasmacytic lymphoma and mucosa-associated lymphoid tissue lymphoma.

Extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) arising in the small intestine with monoclonal cryoglobulinemia

A case of small intestinal extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) with monoclonal cryoglobulinemia is described. The patient was a woman in her mid-sixties with purpura of the bilateral lower legs and abdominal pain. An immunoserological investigation showed expression of IgM-kappa type monoclonal cryoglobulin. A renal biopsy specimen revealed proliferative glomerulonephritis with cryoglobulin deposition. Physical examination disclosed a stenosis, edematous changes and ascariasis in the small intestine. In aspiration cytology of the ascites, proliferation of the atypical lymphoid cells with plasmacytoid differentiation was observed. These cells were positive for B-lineage antigens in immunocytochemistry, and showed an immunoglobulin heavy-chain gene rearrangement in Southern blotting and chromosomal alteration in G-banded karyotype analysis. Although medicinal treatment was used, the patient died of general prostration. The diagnosis of intestinal MALT lymphoma was made at autopsy. Expression of API2-MALT1 fusion transcripts was detected by reverse transcription-polymerase chain reaction analysis using formalin-fixed, paraffin-embedded tissue. Intestinal MALT lymphomas with API2-MALT1 expression have distinctive forms of infiltration compared with those without translocation. Therefore, detection of API2-MALT1 fusion transcripts is useful for evaluating the prognosis and clinical behavior of the disease.

t(11;18)-Bearing Pulmonary Mucosa-Associated Lymphoid Tissue Lymphoma Responding to Cladribine

Mucosa-associated lymphoid tissue (MALT) lymphoma is a low-grade B-cell lymphoma and is usually slow to disseminate. The t(11;18)(q21;q21) translocation has been identified in a subset of MALT lymphoma cases, and AP12 and MLT1/MALT1 genes have been implicated in this translocation. However, the clinicopathologic features of t(11;18)-bearing MALT lymphoma have not been fully elucidated, and the optimal therapy for patients with disseminating disease is unknown. We report an outstanding case of MALT lymphoma that showed massive pulmonary infiltration and leukemic transformation during a prolonged course of more than 16 years. Reverse transcriptase-polymerase chain reaction and dual-color fluorescence in situ hybridization analyses confirmed the existence of the AP12/MLT1 fusion gene in the lymphoma cells. Peripheral blood lymphoma cells disappeared after glucocorticoid therapy. Although the pulmonary lymphoma was slowly progressive and caused severe hypoxemia despite the continuation of glucocorticoid therapy, treatment with cladribine induced a marked reduction of pulmonary lymphomatous lesions and an improvement of the hypoxemia. These findings show the unique clinical features of this particular indolent B-cell lymphoma with t(11;18) translocation and suggest the potential therapeutic usefulness of glucocorticoid and cladribine.

Unfavourable prognosis of patients with trisomy 18q21 detected by fluorescence in situ hybridisation in t(11;18) negative, surgically resected, gastrointestinal B cell lymphomas

BACKGROUND

The most frequent cytogenetic alteration in gastrointestinal (GI) B cell lymphoma (BCL) is t(11;18)(q21;q21). GI B cell non-Hodgkin lymphomas lacking this translocation vary in their biology and clinical outcome. The t(11;18) negative subgroup shows increased numerical changes of chromosome 18, although its clinical relevance remains unknown.

METHODS

Thirty surgically resected primary GI BCLs were examined-11 low grade marginal zone mucosa associated lymphoid tissue (MALT) lymphomas, four marginal zone lymphomas with diffuse large BCL (DLBCL), and 15 de novo DLBCLs. Chromosome 18 aberrations were examined using interphase fluorescence in situ hybridisation. Trisomy 18 was studied applying a centromere 18 probe and a dual colour probe for the MALT1 gene at 18q21.

RESULTS

Using the MALT1 probe, only one marginal zone MALT lymphoma had a break apart pattern, indicating t(11;18) or variants. In the GI BCLs lacking MALT1 breaks, trisomy 18q21 was seen in seven patients (four with complete trisomy 18 and three with partial trisomy of 18q21). Trisomy 18q21 was found in two of 10 low grade MALT lymphomas and five of 19 GI BCLs with large cell component. Six of 17 patients with trisomy 18q21 presented with >/= stage II and one of 12 with stage I disease. Trisomy 18q21 was associated with significantly shorter disease specific survival in the whole group and GI BCLs with large cell component, but not in the low grade group.

CONCLUSIONS

Trisomy 18q21, including MALT1, may be associated with advanced tumour stage and may be a predictor of poor outcome in surgically resected primary GI BCLs.

No evidence of a correlation between BCL10 expression and API2-MALT1 gene rearrangement in ocular adnexal MALT lymphoma

In the present study, 62 cases of ocular adnexal lymphoproliferative disorders were reviewed clinicopathologically. Of them, 51 were extranodal marginal zone B-cell lymphoma (MALT lymphoma), five were diffuse large B-cell lymphoma (DLBCL), one was peripheral T-cell lymphoma, one was NK/T cell lymphoma, nasal type, and four were reactive lymphoid hyperplasia. These lymphoma cases showed a favorable clinical course and localized disease, except for the case of NK/T cell lymphoma, although 19 cases (32.8%) had a recurrence of disease. To clarify the correlation between BCL10 protein expression and API2-MALT1 gene rearrangement, the 51 cases of MALT lymphoma and 5 cases of DLBCL were analyzed by immunohistochemical and RT-PCR methods. Nuclear BCL10 expression was identified in 58% of MALT lymphoma cases, but not in any DLBCL cases. There was no evidence of a correlation between aberrant nuclear BCL10 expression and the clinical parameters examined in the present study. API2-MALT1 transcription was not demonstrated in either the MALT lymphoma cases or the DLBCL cases studied using a multiplex one-tube reverse transcriptase-PCR method. These findings indicate that the nuclear expression of BCL10 is unlikely to correlate with the API2-MALT1 fusion gene in ocular adnexal MALT lymphoma.

Mutual exclusion of t(11;18)(q21;q21) and numerical chromosomal aberrations in the development of different types of primary gastric lymphomas

Gastric non-Hodgkin's lymphomas can be divided histologically into mucosa-associated lymphoid tissue (MALT) lymphoma (ML) and diffuse large cell lymphoma (DLCL) with or without evidence of preceding/accompanying ML (DLCL + ML). We studied the incidence of the most frequent structural chromosomal aberration in ML, t(11;18)(q21;q21), and numerical aberrations of seven chromosomes in 36 ML, 39 DLCL + ML and ten gastric DLCL cases, by dual-colour interphase fluorescence in situ hybridization (FISH) and reverse transcriptase polymerase chain reaction (RT-PCR). t(11;18)(q21;q21) was exclusively detected in ML (FISH 22%; RT-PCR 24%), being completely absent in DLCL + ML and DLCL. No other translocations involving 11q21 or 18q21 and other partner chromosomes were detected by FISH. In lymphomas harbouring t(11;18)(q21;q21), this translocation was the sole genetic abnormality. In contrast, 45% of the t(11;18)(q21;q21)-negative ML showed trisomies, especially of chromosome 3 and 18. In DLCL + ML with separate small and large cell components, trisomies were either detected in both components or occurred exclusively in large tumour cells. Our results suggest that ML can be divided in lymphomas characterized by the t(11;18)(q21;q21), which are unlikely to transform into high-grade tumours, and t(11;18)(q21;q21)-negative ML that may develop into DLCL + ML after the acquisition of additional genetic aberrations.

Detection of Two Cell Populations Corresponding to Distinct Maturation Stages in API-2/MLT-Positive Mucosa-Associated Lymphoid Tissue Lymphoma Cells Proliferating in Pleural Effusion

A 66-year-old man was admitted to our hospital because of an intra-abdominal tumor and pleural effusion (PE). Immunoelectrophoresis of the serum showed immunoglobulin M (IgM) kappa paraprotein (7330 mg/dL). Abnormal plasmacytoid cells were seen in both the peripheral blood (PB) and the bone marrow (BM). Computed tomography scans showed extensive thickening of the gastric wall and bilateral massive PE without lymph node or pulmonary involvement. A histologic examination of the gastric mucosa showed a diffuse infiltration of small- to medium-sized lymphoid CD20-bearing cells, some of which showed a plasmacytoid morphology. Lymphoepithelial lesions were demonstrated with an immunohistochemical stain. The diagnosis was gastric mucosa-associated lymphoid tissue (MALT) lymphoma infiltrating to the PE, PB, and BM. The PE contained numerous lymphoid cells with plasmacytoid morphology that Southern blotting analysis showed to have a monoclonal IgH gene rearrangement pattern. The cells seemed to be divided into two populations according to their surface markers: mature B-cells (CD19+CD20+CD22+CD21+CD38-) and secretory B-cells (CD19+CD20(dim)CD22-CD21-CD38+). The reverse transcriptase-polymerase chain reaction technique detected the API-2/MLT transcript in the PE and PB. The patient had a good response to fludarabine treatment, which was followed with rituximab therapy. In general, gastric MALT lymphoma cells have a tendency to differentiate into plasma cells. In this article, we show that the cell character of API-2/MLT-positive MALT lymphoma is preserved even when the cells are disseminated. This is the first published case, to our knowledge, in which two differentiation stages of MALT lymphoma cells infiltrating into PE have been confirmed by flow cytometric analysis.

T(14;18)(q32;q21) involving IGH and MALT1 is a frequent chromosomal aberration in MALT lymphoma

T(11;18)(q21;q21) is the most common structural abnormality in extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) leading to the fusion of the apoptosis inhibitor-2 (API2) gene and the MALT lymphoma-associated translocation (MALT1) gene. In 2 patients with MALT lymphoma of the liver and skin, respectively, t(14;18)(q32;q21) was observed by cytogenetic analysis. Subsequent fluorescence in situ hybridization (FISH) studies disclosed that the immunoglobulin heavy-chain locus (IGH) and the MALT1 gene were rearranged by this translocation. In order to screen a large series of MALT lymphomas for this aberration, a 2-color interphase FISH assay was established. Among a total of 66 cases, t(14;18)(q32;q21) involving IGH and MALT1 was detected in MALT lymphomas of the liver (4 of 4), skin (3 of 11), ocular adnexa (3 of 8), and salivary gland (2 of 11), but did not occur in MALT lymphomas of the stomach (n = 10), intestine (n = 9), lung (n = 7), thyroid (n = 4), or breast (n = 2). In total, 12 of 66 (18%) MALT lymphomas harbored t(14;18)(q32;q21); 7 additional cases of splenic marginal zone lymphoma tested negative. All of the 12 MALT lymphomas featuring the t(14;18)(q32;q21) were negative for t(11;18)(q21;q21) by reverse transcriptase-polymerase chain reaction (RT-PCR). However, trisomy 3 and/or 18 was found in 4 of 12 cases, suggesting that the t(14;18)(q32;q21) does not occur as the sole genetic abnormality. This study identifies IGH as a new translocation partner of MALT1 in MALT lymphomas, which tend to arise frequently at sites other than the gastrointestinal tract and lung. In contrast to t(11;18)(q21;q21)(+) MALT lymphomas, those with t(14;18)(q32;q21) may harbor additional genetic abnormalities.