Solitary epithelial cells in B cell gastric MALT lymphoma

BACKGROUND: Gastric mucosa associated lymphoid tissue (MALT) lymphoma is a low grade B cell lymphoma histologically characterised by neoplastic B cells surrounding follicles in a marginal zone pattern and selectively infiltrating epithelium to form characteristic lymphoepithelial lesions. AIMS: To identify solitary epithelial cells in gastric MALT lymphoma and investigate their nature. METHODS: Anonymised endoscopic biopsies from eight B cell gastric MALT lymphomas and 10 control biopsies from chronic atrophic gastritis were selected. The numbers of solitary cytokeratin positive epithelial cells were assessed both semiquantitatively and quantitatively in immunostained sections. Chromogranin A expression was studied in sections consecutive to those stained for cytokeratin. RESULTS: Statistical analysis of the quantitative data confirmed that solitary epithelial cells were significantly more common in the lymphomas. The study of consecutive sections showed that the single cells express chromogranin A. CONCLUSIONS: The presence of solitary, cytokeratin positive epithelial cells within the neoplastic infiltrate is a characteristic feature of gastric B cell lymphoma. These solitary epithelial cells are of neuroendocrine origin.     

Clinicopathological features of gastric mucosa associated lymphoid tissue (MALT) lymphomas: high grade transformation and comparison with diffuse large B cell lymphomas without MALT lymphoma features

AIMS: To investigate the clinicopathological differences among gastric low grade MALT lymphomas (low MALT), large B cell lymphomas with low grade components (secondary high grade MALT lymphomas, high MALT), and diffuse large B cell lymphomas without low grade features (primary high grade MALT lymphomas, DLL). METHODS: Clinicopathological and morphological characters of 126 gastric lymphoma cases were studied: 82 cases of low MALT lymphoma including 40 that were surgically resected, 17 cases of high MALT lymphoma including 13 surgically resected, and 27 cases of DLL including 12 surgically resected. RESULTS: Age ranges were as follows: low MALT lymphoma, 34 to 85 years (mean 59.9); high MALT lymphoma, 53 to 88 years (mean 68.5); DLL, 29 to 83 years (mean 62.3). The average age for low and high MALT lymphomas was significantly different (p < 0.05), but there were no differences in other comparisons. There was a female predominance of low MALT lymphoma patients (female to male ratio, 47/35), while for high MALT patients the ratio was almost even (8/9), and for DLL patients there was a male predominance (11/16). Examination of surgically resected material showed that MALT lymphomas had a wider distribution in the gastric wall than DLL. CONCLUSIONS: The findings suggest that at least some of the high grade gastric lymphomas, especially in patients younger than the fifth decade, do not originate from high grade transformation of low MALT lymphomas. It seems to take about one decade at least for high grade transformation of low MALT lymphomas.     

Immunoglobulin specificity of low grade B cell gastrointestinal lymphoma of mucosa-associated lymphoid tissue (MALT) type.

The specificity of the tumor cell immunoglobulin in three cases of low grade B cell gastrointestinal mucosa-associated lymphoid tissue (MALT) lymphoma has been studied. Using anti-idiotypic antibodies to detect the reactivity of tumor immunoglobulin in tissue sections from the patients and other individuals, we observed specificity for normal tissue components in all three cases studied. Reactivity in one case was with follicular dendritic cells, in the second case with a novel antigen on mucosal post capillary venules, and, in the third case, a broad pattern of reactivity was observed. This study suggests that autoimmunity may play a role in the pathogenesis of gastric lymphoma.     

Low grade MALT lymphoma of the stomach: treatment outcome with radiotherapy alone

In order to evaluate the role of radiation therapy in the management of low-grade mucosa-associated lymphoid tissue lymphoma of the stomach (MLS), in patients with no evidence of Helicobacter pylori (H. pylori) or who had not responded to H. pylori eradication treatment, we analyzed the treatment outcome of patients who had received radiotherapy alone. Between Jan 1995 and May 2001, 6 patients with low- grade MLS were treated with radiotherapy alone. The median radiation dose was 30.6 Gy (range; 30 - 39 Gy) in a daily fractions of 1.5 - 1.8 Gy. Each patient had an endoscopic esophago-gastro-duodenoscopy with biopsy, 4 weeks after the completion of radiotherapy and every 6 months thereafter. A complete response was obtained in all patients. All patients were followed-up without evidence of disease, and no patient suffered a relapse. There was neither perforation nor hemorrhage of the stomach in any of the patients. No renal or hepatic toxicity were noted, and no secondary malignancies developed. In conclusion, radiotherapy should be considered as the preferred treatment method for low-grade MLS, in patients with no evidence of H. pylori infection, or who do not respond to antibiotic therapy, due to the significant benefits in gastric preservation and low morbidity.     

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.     

Genetic evidence for a clonal link between low and high-grade components in gastric MALT B-cell lymphoma

High-grade MALT lymphomas often contain low-grade tumour components; both cell populations have been shown to express the same immunoglobulin light chain previously. However, the clonal link between the low and high-grade components has not been established at the genetic level. To investigate this link, we have examined low- and high-grade components microdissected from tissue sections of four high-grade gastric MALT lymphomas. PCR and sequence analyses were performed to identify clone-specific rearranged immunoglobulin heavy chain gene sequences. In each of these cases, the PCR products from the two components were identical in size by electrophoresis. Direct sequencing revealed common clone-specific immunoglobulin heavy chain gene rearrangements in both lesions of each case, providing genetic evidence for a clonal link. These results support the proposal that high-grade MALT lymphomas generally evolve from low-grade clones.     

Detection of Helicobacter pylori associated antigen and heat shock protein 60 on follicular dendritic cells in the germinal centres of low grade B cell lymphoma of gastric mucosa associated lymphoid tissue (MALT).

AIMS: To investigate the localisation of Helicobacter pylori antigens and the expression of human heat shock proteins (HSP) in stomachs affected by MALT lymphoma. METHODS: Surgically resected stomachs from 24 patients with MALT lymphoma were immunostained with anti-H pylori rabbit antibodies (ORP-1 and ORP-2) and anti-human HSP60 mouse monoclonal antibodies (mAb) (LK-1 and LK-2). RESULTS: Follicular dendritic cells of germinal centres in the stomachs affected by MALT lymphoma were immunostained with anti-H pylori polyclonal antibodies and with anti-human HSP60 mAb, as were the epithelial cells. None of the lymph node samples reacted. CONCLUSIONS: Human HSP60, which cross reacts with anti-H pylori polyclonal antibodies, is often expressed on follicular dendritic cells in gastric MALT lymphoma tissues and may be aetiologically relevant to lymphomagenesis of MALT lymphoma.     

Expression of cdc2 and cyclin B1 in Helicobacter pylori-associated gastric MALT and MALT lymphoma : relationship to cell death, proliferation, and transformation

Mucosa-associated lymphoid tissue (MALT) may accumulate within gastric mucosa as a result of long standing Helicobacter pylori infection, and this acquired MALT may eventually develop into low-grade B-cell MALT lymphoma. To determine the possible association of cell cycle regulatory proteins and apoptotic cell death in the transformation of H. pylori gastritis to MALT lymphoma, the extent of cell proliferation, cell viability, expression of Cdc2/Cdk1 and cyclin B in gastric mucosal from patients with H. pylori-positive chronic gastritis (n = 7), MALT (n = 12), or MALT lymphoma (n = 12) were undertaken. Control tissue was obtained from H. pylori- negative patients (n = 5). Proliferating cell nuclear antigen (PCNA), Cdc2, and cyclin B1 were examined in paraffin embedded tissue by immunohistochemistry, while the apoptotic index (AI) was determined using the TUNEL assay. H&E staining for histology and modified Giemsa staining for the detection of H. pylori was conducted simultaneously. When compared to chronic gastritis tissue, those with MALT or MALT lymphoma had an increase in PCNA labeling index of 3.3- and 2.7-fold, while that for Cdc2/Cdk1 increased 2.3- and 3.1-fold, respectively. cyclin B1 labeling was 1.9 and 3.0 fold, while the AI was 3.4- and 1.4-fold higher in MALT and MALT lymphoma tissue, respectively, in the same comparison. On the other hand, the AI index of MALT lymphoma was 2. 5-fold lower than that for MALT tissues. The labeling scores for Cdc2/Cdk1 and cyclin B1 were significantly higher in the germinal center when compared to the mantle and marginal zones of MALT tissues. Using chi(2) and Pearson/Spearman's rho correlation coefficient with regression analyses, there was an inverse correlation between the AI and Cdc2/Cdk1 or cyclin B1 in MALT and MALT lymphoma tissues. There was no correlation between AI and PCNA labeling in any of the tissues. These results suggest that Cdc2/Cdk1 and cyclin B1 expression may be actively associated in the modulation of cellular death by apoptosis, as well as cellular proliferation and transformation during the evolution of H. pylori-associated gastritis to MALT lymphoma. Subclassification of high labeling score (>/=40) for Cdc2/Cdk1 and cyclin B1 and low labeling index (<0.6) for apoptotic cells in H. pylori-associated MALT may help in identifying a population of patients with an increased risk of developing MALT lymphoma.     

Synchronous adenocarcinoma and low grade B-cell lymphoma of mucosa associated lymphoid tissue (MALT) of the stomach

We describe nine cases of gastric adenocarcinoma (six intestinal and three diffuse type) occurring in the stomach synchronously with primary low grade B-cell lymphoma of mucosa associated lymphoid tissue. In four cases the two neoplasms were admixed to form collision tumours. Where collision was present between lymphoma and adenocarcinoma of intestinal type no lymphoepithelial lesions were seen involving neoplastic glands. Helicobacter pylori-like organisms were seen in seven cases (78%) which is consistent with an aetiological role for this organism in both tumours in the stomach.     

The bcl-2 gene in primary B cell lymphoma of mucosa-associated lymphoid tissue (MALT).

The bcl-2 gene rearrangement representing t(14:18) chromosomal translocation is the most frequent karyotypic abnormality in non-Hodgkin's lymphomas of follicle center-cell lineage. By using three bcl-2 DNA probes, 21 cases of non-Hodgkin's B cell lymphoma arising from gastrointestinal mucosa and eight cases of follicular lymphomas were examined. No rearrangement of the gene could be detected in the group of gastrointestinal lymphomas, although it was identified in 75% of the follicular lymphomas. The findings suggest that these two groups of lymphomas are not a family at genetic level and support the earlier suggestion that B cell lymphomas arising from gastrointestinal mucosa-associated lymphoid tissue are not of follicle center-cell lineage.     

B cell reconstitution after rituximab treatment of lymphoma recapitulates B cell ontogeny

The long-term immunologic effects of B cell depletion with rituximab and the characteristics of the reconstituting B cell pool in lymphoma patients are not well defined, despite the widespread usage of this therapy. Here we report that during the B cell reconstitution phase a majority of the peripheral blood B cells have an immature transitional phenotype (47.8%+/-25.2% vs. 4.4%+/-2.4% for normal controls, p<0.0001), similar to what has been described during the original ontogeny of the immune system and following bone marrow transplantation. Moreover, the recovery of the CD27+ memory B cell pool was delayed compared to normal B cell ontogeny, remaining below normal controls at 1 year post-rituximab (4.4%+/-3% vs. 31%+/-7%, p<0.0001). Expansion of functionally immature B cells and decreased memory B cells may contribute to an immunodeficient state in patients recovering from rituximab mediated B cell depletion, particularly with repeated treatment.     

Establishment of a novel MALT lymphoma cell line, ma-1, from a patient with t(14;18)(q32;q21)-positive Helicobacter pylori-independent gastric MALT lymphoma

Although t(11;18)(q21;q21), t(1;14)(p22;q32), and a few other genetic mutations are specific markers for the Helicobacter pylori (HP)-independent status of gastric mucosa-associated lymphoid tissue (MALT) lymphoma, the molecular mechanisms responsible for HP-independence of gastric MALT lymphoma without such translocations and mutations remain uncharacterized. In the present study, we describe the establishment and characterization of a novel MALT lymphoma cell line, MA-1, which was derived from a gastric MALT lymphoma which was negative for both t(11;18)(q21;q21) and t(1;14)(p22;q32); the patient had failed HP eradication therapy and chemotherapy. The cell morphology and the immunophenotype of this cell line were similar to that of the original gastric MALT lymphoma. Comparative genomic hybridization analysis showed no significant gene copy number changes. Spectral karyotyping displayed a near-diploid chromosome content (48 < 2n>XY), with at least 13 chromosome structural abnormalities. Furthermore, fluorescence in situ hybridization analyses disclosed the existence of three sub-clones, characterized by t(14;18)(q32;q21)/IGH-BCL2, t(14;18)(q32;q21)/IGH-MALT1, and the presence of both chromosomal translocations in the same cell, respectively; whereas amplification of the genes CRAD9, TRAF2, and BCL10 were not found. In conclusion, we have established the first human gastric MALT lymphoma cell line, which is characterized by unusual and complex chromosome translocations and will be useful to explore further the molecular mechanisms of HP-independence in gastric MALT lymphoma.     

MALT lymphoma of the intestine. A clinicopathological study over a period of 13 years

Clinicopathological features of 14 patients with histologically confirmed primary intestinal Non-Hodgkin lymphoma were analysed. Patients were mostly young males with median age of 27.2 years. Main presenting features was intestinal obstruction. Diffuse large cell lymphoma was the commonest histological type. All cases were found to be B cell type in immunohistochemistry.     

Histological and immunological parameters to predict treatment outcome of Helicobacter pylori eradication in low-grade gastric MALT lymphoma

Helicobacter pylori eradication is generally accepted as the first choice of treatment for stage IE low-grade gastric MALT lymphoma (mucosa-associated lymphoid tissue-type lymphoma). Treatment failure may be attributed to the extent of the disease and to progression into an antigen-independent phase. This study assessed the value of morphological grading and the expression of the co-stimulatory markers CD40, CD80 and CD86 and their ligands to predict clinical outcome in 23 consecutive low-grade MALT lymphoma patients treated with H. pylori eradication. Complete regression was achieved in 13/23 patients (56%), partial regression in two (9%), and no response in eight (35%). Histological grading was highly predictive of clinical response, especially in stage IE(1) patients, with complete remissions in 10/12 tumours with purely low-grade (type A) morphology and 1/8 tumours with increased numbers of blasts (type B) (p=0.0046) and was related to the expression of costimulatory markers (p=0.0061). Moreover, CD86 as a single marker proved to be of predictive value for treatment outcome (p=0.0086). These results suggest that morphological grading and immunological criteria can be defined to recognize the transition into the antigen-independent phase of gastric MALT-NHL. In addition to clinical stage, these critera may in future serve as a practical pathological guide to the choice of therapy.     

Low-grade gastric B-cell lymphoma of mucosa-associated lymphoid tissue (MALT): a multifocal disease

Gastrectomy specimens from five patients following gastroscopic biopsies which showed low-grade B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) were examined by serially sectioning and paraffin wax embedding using a 'swiss roll' technique. This procedure allowed the construction of a map of the specimen on which the distribution of the lymphoma could be plotted. In each case confluent lymphoma was identified. In addition small foci of lymphoma consisting of 1-4 lymphoid follicles surrounded by neoplastic centrocyte-like cells were seen. The positions of these 'micro-lymphomas' were plotted on the gastrectomy maps, showing multiple foci distributed throughout the gastric mucosa. The identification of these microscopic lesions may explain the development of local relapse, often after a long disease-free interval, in patients with gastric MALT lymphoma treated by partial gastrectomy where excision appears to have been complete. Patients treated in this way should, therefore, be followed-up indefinitely, with regular endoscopy and gastric biopsy, in order to identify early local disease relapse.     

Establishment and characterization of a MALT lymphoma cell line carrying an API2‐MALT1 translocation

MALT lymphomas with API2(BIRC3)‐MALT1 translocation usually have an indolent clinical course and rarely transform into aggressive lymphoma, and there have been no lymphoma cell lines carrying API2‐MALT1 translocation reported to date. We established a novel lymphoma cell line named BMA19, carrying the API2‐MALT1 translocation from a patient with histologic transformation of intestinal MALT lymphoma. The cells were suggested to carry API2‐MALT1 and MYC‐IGH translocations by chromosomal analysis, and these translocations were confirmed by polymerase chain reaction analysis. The expression of MYC was shown to be enhanced as a result of the MYC‐IGH translocation, and it is considered to have played a role in the histologic transformation of MALT lymphoma. Whole exome sequencing of BMA19 identified several nucleotide variations in genes reported to be mutated in previous studies of marginal zone lymphomas. The MALT1 inhibitor MI‐2 specifically decreased cell growth, and the BMA19 cell line was suggested to be still dependent on the API2‐MALT1 signal. Subtractive microarray analysis showed that one of the earliest events resulting from MALT1 inhibition is increased susceptibility to endoplasmic reticulum stress‐induced apoptosis. The BMA19 cell line is considered to conserve the biological properties of MALT lymphoma and is expected to be a valuable tool for research into the pathogenesis of MALT lymphoma with an API2‐MALT1 translocation.