B-cell clonality and infection with Helicobacter pylori: implications for development of gastric lymphoma

Application of the BIOMED-2 standardized primer system for the diagnosis of primary gastric B-cell non-Hodgkin's lymphoma

Primary gastric B-cell non-Hodgkin's lymphoma (B-NHL) has a similar morphocytological presentation to severe chronic gastritis, which complicates the pathological diagnosis of this disease. To investigate the practicality and utility of the BIOMED-2 standardized primer system for the diagnosis of primary gastric B-NHL from endoscopic biopsy specimens, we selected 65 cases of archived paraffin-embedded primary gastric B-NHL specimens as well as 27 cases of severe chronic gastritis samples to serve as a negative control group. The positivity rates of immunoglobulin heavy chain (IgH) gene rearrangements detected by the BIOMED-2 standardized primer system for the two groups were 86.4% and 12.0%, respectively, which are significantly different (p < 0.05). Importantly, the combined detection of the five groups of the IgH primer system increased the detection rate of B-NHL. These findings indicate that the BIOMED-2 standardized primer system is suitable for formalin-fixed and paraffin-embedded (FFPE) specimens and is valuable as a secondary diagnostic tool for primary gastric B-NHL as well as the differential diagnosis of severe chronic gastritis.

Endoscopic and histologic analysis of gastric mucosa-associated lymphoid tissue in children with Helicobacter pylori infection

OBJECTIVES

Nodular gastritis (NG) associated with Helicobacter pylori infection can occur commonly in childhood and is regarded to be benign without clinical significance. This study includes endoscopic and histologic analysis of gastric mucosa-associated lymphoid tissue (MALT) to clarify the significance of NG on endoscopy in H pylori-infected children.

METHODS

Of the 758 children who underwent endoscopy, 80 were identified as having H pylori infection. These patients were divided into 3 groups based on endoscopic severity of gastric nodularity. Histopathologic grading of MALT and immunohistochemistry of CD3, CD20, cytokeratin, and Ki-67 were evaluated.

RESULTS

On endoscopy, severe NG was observed in the antrum of 38 of the 80 subjects, mild NG in 27, and an absence of NG in 15. Density of H pylori and lymphocyte infiltration differed among the 3 groups (P=0.022 and P=0.025, respectively). Histological grading for gastric lymphoid infiltrates was compatible with grade 1 in 47 (58.8%), grade 2 in 21 (26.3%), grade 3 in 7 (8.8%), and grade 4-5 in 4 (5.1%) in the antrum. Degree of NG, density of H pylori, neutrophil activity, and gastritis score in the antrum varied with MALT grades (P=0.003, P=0.042, P=0.028, and P=0.006, respectively).

CONCLUSIONS

Our study suggests NG may present as a significant gastric manifestation of childhood H pylori infection that indicates gastric MALT. Thorough histologic investigation may be useful in the evaluation of gastric MALT in children infected with H pylori that manifests as severe NG in the antrum.

Crystalline plasma cell inclusions in helicobacter-associated gastritis

BACKGROUND

Crystalline cytoplasmic inclusions are well documented in B cell lymphomas but have rarely been described in reactive plasmacytic infiltrates.

AIM

Three cases of Lelicobacter-associated gastritis are described in which plasma cells focally contained rhomboid and needle-shaped crystalline inclusions.

METHODS

Crystalline inclusions were identified in the gastric biopsy specimens from three patients undergoing routine upper gastrointestinal endoscopy. The cells were characterised immunohistochemically using the following antisera: cytokeratin, leucocyte common antigen, desmin, CD20, CD68, CD79a, CD138, immunoglobulin (Ig)G, IgA and IgM heavy chains, and kappa and lambda Ig light chains. Clinical follow-up data were obtained.

RESULTS

All biopsies showed a Lelicobacter-associated active chronic gastritis. Variable numbers of plasma cells with intracytoplasmic crystalline inclusions in the superficial lamina propria were seen. The crystals were not stained with any of the antisera tested, but the cells containing the crystals expressed CD79a and CD138 and, in the two assessable cases, showed IgA and lambda light chain immunoreactivity. The more numerous morphologically normal plasma cells in each patient were polytypic, and there were no histological features to suggest lymphoma. Crystals were not identified in the plasma cells in mucosal biopsy specimens from other sites in any of the patients.

CONCLUSIONS

Crystalline inclusions in plasma cells can occur in association with Lelicobacter gastritis. Although light chain restriction was shown in two patients, the overall histological and clinical findings indicated a reactive process. The presence of plasma cell crystals in isolation should not be considered to be diagnostic of lymphoma.

Combined histology and molecular biology for diagnosis of early stage gastric MALT lymphoma

OBJECTIVE

To establish a sequential diagnostic procedure of gastric mucosa-associated lymphoid tissue (MALT) lymphoma and provide evidence for selected optimal cases to be treated in the early stage.

METHODS

Thirty-one cases of gastric lymphoid hyperplasia (GLH) were selected and multiple investigations including histology, protein level, DNA and chromosome levels, combined with clinical follow-up were performed. Histological grade was according to Isaacson's criteria of GLH; CD20, UCHL-1 (CD45RO), anti-kappa (kappa), anti-lambda (lambda) and Ki-67 were used for immunohistochemical staining; semi-nested polymerase chain reaction (PCR) was used to detect IgH gene rearrangement and reverse-transcription PCR (RT-PCR) was used to detect API2-MALT1 fusion of the chromosome translocation t(11;18)(q21;q21). Twenty-nine cases underwent eradication therapy for Helicobacter pylori. Changes in histological grade, endoscopic appearance, expression of Ki-67 and IgH gene rearrangement were compared after eradication treatment.

RESULTS

Of the 31 cases of GLH with predominant chronic gastritis and gastric ulcer most were histological grade 2 and 3. Only one case had lambda light chain restriction and 10 cases had monoclonal IgH gene rearrangement. Expression of Ki-67 and monoclonal IgH gene rearrangement were significantly increased with increased lymphoid hyperplasia (P < 0.05). Two cases had API2-MALT1 fusion. Helicobacter pylori was eradicated in 25 cases and another course of treatment had to be given in 4 cases. All cases were followed up for 1.5-37 months. Of the 27 successful eradication cases, 18 showed complete regression both histologically and endoscopically, 4 had partial regression and 7 were unchanged.

CONCLUSIONS

A sequential diagnostic procedure based on histology, expression of Ki-67 combined with clonality of IgH rearrangement and API2-MALT1 fusion helps to diagnosis of early stage gastric MALT lymphoma and choose the best treatment strategy.

Wotherspoon criteria combined with B cell clonality analysis by advanced polymerase chain reaction technology discriminates covert gastric marginal zone lymphoma from chronic gastritis

BACKGROUND AND AIMS

Gastric mucosa associated lymphoid tissue lymphoma is a well defined B cell lymphoma yet often impossible to distinguish from severe chronic gastritis on morphological grounds alone. Therefore, it was suggested to use the clonality of the immunoglobulin (Ig) heavy chain (H) genes, as detected by polymerase chain reaction (PCR), as a decisive criterion. However, there is controversy as to whether B cell clonality also exists in chronic gastritis, hence rendering this approach futile at present.

METHODS

An expert panel re-examined the histology and immunohistochemistry of a total of 97 cases of gastric biopsies, including clearcut marginal zone lymphoma, chronic gastritis, and ambiguous cases, applying the Wotherspoon criteria on the basis of haematoxylin-eosin and CD20 immunostainings. In addition, a new and advanced PCR system for detection of clonal IgH gene rearrangements was independently applied in two institutions in each case.

RESULTS

The overall IgH clonality assessments of both institutions were in total agreement. Overt lymphoma (Wotherspoon score 5) was clonal in 24/26 cases. Chronic gastritis (Wotherspoon scores 1 and 2) was not clonal in 52/53 cases; the clonal case being Wotherspoon score 2. Of 18 cases with ambiguous histology (Wotherspoon scores 3 and 4) four were clonal.

CONCLUSIONS

Using advanced PCR technology, clonal gastritis is extremely rare, if it exists at all. Thus B cell clonality in Wotherspoon 3 and 4 cases is regarded as suitable for definitively diagnosing gastric marginal zone lymphoma.

Instability of clonality in gastric lymphoid infiltrates: a study with emphasis on serial biopsies

The evolution of low-grade B-cell mucosa-associated lymphoid-tissue (MALT) lymphoma of the stomach is a multistage process, reflected in the histologic continuum from Helicobacter pylori-chronic gastritis, to low-grade and high-grade lymphoma. Interestingly, in daily gastric biopsy sign-out, the authors observed that some biopsies showed monoclonality on polymerase chain reaction (PCR) even though there were no definite histologic features of malignancy and vice versa. To address the question, the authors studied the endoscopic gastric biopsies at first presentation of 46 patients to examine any clonality differences among various histologic patterns within the spectrum of MALT lymphoma evolution. The gastric biopsies were reviewed histologically and graded according to the Wotherspoon-Isaacson histologic scoring system from grade 0 (normal) to grade 5 (MALT lymphoma). The clonality of cases in each grade was determined by performing nested PCR for immunoglobulin heavy chain (IgH) gene rearrangement using FR2/JH and FR3/JH primer sets. The monoclonality rates among different grades were as follows: grade 2, 6.3% (1 of 16); grade 3, 27.3% (3 of 11); grade 4, 83.3% (5 of 6); grade 5, 69.2% (9 of 13). Statistically significant difference of monoclonality rate is demonstrated in histologic grade 4 versus grades 2 and 3, and grade 5 versus grade 2 (P < 0.05, Fisher exact test). The authors went on to examine the progress of disease by following up the clinical status, histologic changes, and clonality fluctuation of these cases. Four of the 8 patients with monoclonality on PCR, but no definite lymphoma at first presentation later progressed to frank MALT lymphoma. Our study shows that, during the progression to MALT lymphoma, there is an instability of clonality. Clonality can fluctuate between polyclonality, oligoclonality, and monoclonality, none of which defines an irreversible stage for progression to MALT lymphoma. Monoclonality is a risk factor for development of MALT lymphoma. Those cases with dense gastric mucosal lymphoid infiltrate (without definite MALT lymphoma) and monoclonality on PCR need to be closely monitored and Helicobacter infection promptly treated if present. In combination with clinicohistologic examination, PCR can serve as a complementary tool in arriving at a definite diagnosis of MALT lymphoma in cases with borderline histologic features.

Molecular analysis of B-cell clonality in Helicobacter pylori gastritis

The aim of our study was to identify PCR-detectable clonal B-cell population in Helicobacter pylori gastritis and assess their relation to the Wotherspoon-Isaacson (W-I) grade for gastric lymphoid infiltrates. Amplified DNA was obtained from thirty four H. pylori positive gastritis dyspeptic patients and thirty four H. pylori negative matched controls. Clonal bands were observed in 6 (2/17 W-I Grade 1, 2/13 W-I Grade 2, and 2/4 W-I Grade 3 lesions) and polyclonal smears in 24 cases (15 W-I Grade 1, 7 W-I Grade 2, and 2 W-I Grade 3). Four additional W-I Grade 2 samples with clonal bands were associated with background polyclonal smear and were not reproducible. Clonal bands were not recorded in controls. B-cell clonality was not related to W-I grades. We conclude that certain H. pylori positive gastritis patients show PCR-detectable monoclonality, which is independent of the W-I grade of gastritis and cannot be taken as evidence of an existing neoplastic lesion.

Gastrointestinal lymphoma: where morphology meets molecular biology

Primary gastrointestinal lymphomas are best exemplified by mucosa-associated lymphoid tissue (MALT) lymphoma of the stomach and enteropathy-type T-cell lymphoma (ETL). Both lymphomas were initially recognized on morphological grounds and their identification as distinct clinicopathological entities has subsequently been vindicated following integrated immunophenotypic, molecular, and cellular biological investigations. Delineation of the phenotypic, molecular, and biological properties of these lymphomas at various clinicopathological stages of their development has also provided critical information for the clinical management of patients with these diseases. Here, the histopathology and recent advances in phenotypic and molecular characterization of gastric MALT lymphoma and ETL and their applications in diagnosis and clinical management are reviewed.

Helicobacter pylori associated antigastric autoantibodies: role in Sjögren's syndrome gastritis

BACKGROUND

Previous studies have shown that Helicobacter pylori seroprevalence in Sjögren's syndrome is comparable with that of the general population. However, the origin of the chronic gastropathy associated with this syndrome and the role of local autoimmunity--possibly triggered by bacterial infection--in its pathogenesis remain unclear.

MATERIALS AND METHODS

We initially determined the prevalence of IgG anti H. pylori in dyspeptic subjects with and without Sjögren's syndrome. In subsets of both groups we then determined anti CagA and human tissue-tested anticanalicular/antifoveolar autoantibodies. We also compared activity, atrophy and Mucosa Associated Lymphoid Tissue (MALT) scores, as well as symptoms, before and after bacterial eradication.

RESULTS

Prevalence of H. pylori in Sjögren's syndrome patients was similar to controls: 31/54 (57%) vs. 93/150 (62%). Anti CagA prevalence was also similar in the two groups. Twenty weeks after H. pylori eradication, histological activity decreased in both groups, however, atrophy and MALT decreased significantly only in controls. Sixteen months after H. pylori eradication, 75% of Sjögren's syndrome patients still complained of dyspepsia compared with 13% of controls. Finally, antigastric autoantibodies were present in 29% of tested Sjögren's syndrome patients vs. 28% of controls.

CONCLUSIONS

H. pylori infection was equally prevalent among dyspeptic Sjögren's syndrome patients and dyspeptic controls. Likewise, there were no differences regarding anti CagA prevalence or antigastric autoantibodies among the two groups. The persistence of symptoms as well as of the lymphocytic infiltration and atrophy after H. pylori eradication in Sjögren's syndrome may underlie the 'endogenous' and still unknown nature of the gastropathy in this condition.

Oxidative damage of the gastric mucosa in Helicobacter pylori positive chronic atrophic and nonatrophic gastritis, before and after eradication

BACKGROUND

Helicobacter pylori is the main cause of gastritis and a primary carcinogen. The aim of this study was to assess oxidative damage in mucosal compartments of gastric mucosa in H. pylori positive and negative atrophic and nonatrophic gastritis.

MATERIALS AND METHODS

Five groups of 10 patients each were identified according to H. pylori positive or negative chronic atrophic (Hp-CAG and CAG, respectively) and nonatrophic gastritis (Hp-CG and CG, respectively), and H. pylori negative normal mucosa (controls). Oxidative damage was evaluated by nitrotyrosine immunohistochemistry in the whole mucosa and in each compartment at baseline and at 2 and 12 months after eradication. Types of intestinal metaplasia were classified by histochemistry.

RESULTS

Total nitrotyrosine levels appeared significantly higher in H. pylori positive than in negative patients, and in Hp-CAG than in Hp-CG (p <.001); no differences were found between H. pylori negative gastritis and normal mucosa. Nitrotyrosine were found in foveolae and intestinal metaplasia only in Hp-CAG. At 12 months after H. pylori eradication, total nitrotyrosine levels showed a trend toward a decrease in Hp-CG and decreased significantly in Hp-CAG (p =.002), disappearing from the foveolae (p =.002), but remaining unchanged in intestinal metaplasia. Type I and II of intestinal metaplasia were present with the same prevalence in Hp-CAG and CAG, and did not change after H. pylori eradication.

CONCLUSIONS

Oxidative damage of the gastric mucosa increases from Hp-CG to Hp-CAG, involving the foveolae and intestinal metaplasia. H. pylori eradication induces a complete healing of foveolae but not of intestinal metaplasia, reducing the overall oxidative damage in the mucosa.

B-cell monoclonality is associated with lymphoid follicles in gastritis

The gold standard for diagnosis of gastric MALT lymphoma is histopathology. Polymerase chain reaction-based assays to detect the expansion of monoclonal B cells have also been used to corroborate the diagnosis. However, there are conflicting data on monoclonal B-cell expansion in gastritis. We asked about its frequency in graded gastritis cases. Lymphocytic infiltration in gastric biopsies was graded according to Wotherspoon in 129 cases. The histologic diagnosis ranged from normal gastric mucosa to suspicious for gastric MALT lymphoma. To search for a monoclonal B-cell population, a semi-nested polymerase chain reaction strategy was used for amplification of rearranged VDJ sequences of the immunoglobulin heavy chain gene. Of 106 evaluable samples, 18 were found to be monoclonal. The detection of a monoclonal B-cell population was strongly associated with the presence of lymphoid follicles. In cases with lymphoid follicles, detection of monoclonality was independent of Wotherspoon grading; there is no significant difference between cases being suspicious for lymphoma and those not. We found B-cell monoclonality to be a more frequent than expected finding in gastritis and to be strongly associated with the presence of lymphoid follicles; thus, its presence is of little significance in patient management.

Gastric lymphoma: the revolution of the past decade

BACKGROUND

Gastric MALT type lymphomas are distinct lymphomas that may develop after chronic antigenic stimulation caused by infection with Helicobacter pylori. An early antigen-dependent phase precedes the development of an antigen-independent phase.

METHODS

Narrative review.

RESULTS

The causative relationship between a chronic H. pylori infection and gastric MALT lymphomas has been based on epidemiological, histological, experimental and therapeutic studies. H. pylori eradication leads to a histological remission in +/- 70% of patients in early stage low-grade MALT lymphoma. There is no basis for therapeutic consequences in the case of persistent monoclonality. Full thickness invasion of the gastric wall and lymph node involvement and/or high-grade lymphoma denote the transition to an antigen-independent phase and calls for conventional treatment modalities. Molecular findings show a specific translocation in low-grade MALT lymphomas: t(11,18) and nuclear expression of bcl-10 that are highly indicative of the transition of the antigen-dependent into the antigen-independent phase. Other chromosomal and molecular findings are probably also involved.

CONCLUSION

The multistep pathogenesis of chronic H. pylori gastritis into low-grade gastric MALT lymphoma and tumour progression to a higher stage and grade are characterized by multiple molecular biological events. Antigen-dependency during the early phase of this malignancy is proven by the results of H. pylori eradication.

Molecular diagnostics in low-grade gastric marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue type after Helicobacter pylori eradication therapy

The primary gastric lymphomas are extranodal non-Hodgkin's lymphomas that likely originate from the mucosa-associated lymphoid tissue (MALT). Data suggest that chronic infection with Helicobacter pylori (H pylori) is significantly associated with the pathogenesis of low-grade gastric MALT lymphomas. This is in keeping with the observation that many patients with early low-grade MALT lymphomas have complete remissions after H pylori eradication therapy. However, the stability of these remissions remains unclear and relapses have been reported. It can be difficult to distinguish between early malignant and benign disorders of the gastric mucosa. A polymerase chain reaction (PCR) assay can detect rearrangements of the variable region of immunoglobulin heavy chains. This assay can be used to distinguish the clonality of B lymphocytes and has been investigated as a test for differential diagnosis of MALT lymphomas. Monoclonality is observed in the majority of MALT-lymphoma samples at diagnosis but has been found in gastritis samples as well. Whether the presence of monoclonal B cells is associated with the risk of lymphoma progression remains unclear. As many as 50% of patients who have complete histologic remissions of MALT lymphoma after H pylori eradication therapy have persisting monoclonal bands in follow-up PCR monitoring. Although it is unclear as to whether monoclonality indicates the presence of minimal residual disease, patients who have persistent monoclonal bands during follow-up should be considered at risk for relapse. The PCR assay for rearrangements of the variable region of the immunoglobulin heavy-chain gene appears to be of low value in the diagnosis of B-cell malignancies but could provide a useful tool in the follow-up of patients who achieve remissions after H pylori eradication.

Are lymphocytic monoclonality and immunoglobulin heavy chain (IgH) rearrangement premalignant conditions in chronic gastritis?

Normal gastric mucosa is devoid of lymphoid cells. Any increase of lymphocytes suggests chronic inflammation. Infection with Helicobacter pylori (Hp) is the major cause for nonautoimmune chronic gastritis and induces a mixed cellular response resulting in an acquired lymphoid tissue, or MALT (mucosa-associated lymphoid tissue). Hp has also been implicated in the genesis of gastric MALT-lymphoma. Polymerase chain reaction-based assays to detect the expansion of monoclonal B-cells have also been used to corroborate the diagnosis. In a considerable number of cases monoclonal B-cells remain detectable in follow-up biopsies, with the lymphoma being in complete histological remission. The clinical relevance of this finding is not clear yet. However, there also exist different reports that monoclonal B-cells can be found in gastric biopsies of patients with neither a histological sign nor a present or past history of lymphoma. In the light of these findings we address the question whether B-cell monoclonality can be seen as a premalignant condition in chronic gastritis and conclude that as of now the relevance of the finding of B-cell monoclonality remains unclear. As of now the only and gold standard for the diagnosis of gastric MALT-lymphoma is histopathology.

MALT Lymphomas

This review addresses the biology and the treatment of lymphomas arising from mucosa-associated lymphoid tissue (MALT). This entity, first described in 1983, represents about 8% of all non-Hodgkin's lymphomas and was recently re-classified as "extranodal marginal zone lymphomas of MALT-type." The term marginal zone lymphoma (MZL) encompasses the three closely related lymphoma subtypes of nodal, primary splenic and extranodal lymphomas of MALT type: the latter represent the vast majority of MZL. These lymphomas arise at different anatomic sites, are composed of mature B-cells lacking expression of CD5 and CD10, often present with overlapping morphologic features, but typically quite distinct clinical behaviors. Only very recently cytogenetic/molecular genetic observations have underlined the distinctiveness of these three lymphoid neoplasms, which in both the R.E.A.L. and WHO-classifications are included in the general term of MZL. MALT lymphomas arise in numerous extranodal sites, but gastric MALT lymphoma is the most common and best studied and is, therefore, the paradigm for the group as a whole. Dr. Isaacson describes the principal histological features of these lymphomas, including criteria to distinguish this entity from other small B-cell lymphomas. Several lines of evidence suggest that gastric lymphoma arises from MALT acquired as the result of aH. pyloriinfection. However, at least 1/3 of cases do not respond to eradication ofH. pylori. Very recent data suggest that both t(11;18) (q21;q21) and bcl10 nuclear expression are associated with failure to respond to this treatment. Dr. Gascoyne discusses the biologic function of proteins deregulated through the different translocations, which play a role in pathogenesis of MALT lymphomas, emphasizing particularly their influence in disrupting the apoptotic pathway. Dr. Zucca reviews findings suggesting that MALT lymphoma is an antigen driven neoplasm. He also presents specific guidelines for treatment of gastric lymphomas trying to shed some light on the amazingly inconsistent and confusing data in the literature. Taking advantage on the more than 300 non-gastric MALT lymphomas collected by the International Extranodal Lymphoma Study Group (ILESG), Dr. Cavalli compares gastric lymphomas with those arising in many other sites. Overall, the data presented in this session will underline the fact, that MALT lymphomas are characterized by some unique biological properties.

A comprehensive review of the natural history of Helicobacter pylori infection in children

Across populations of children, Helicobacter pylori prevalence ranges from under 10% to over 80%. Low prevalence occurs in the U.S., Canada, and northern and western Europe; high prevalence occurs in India, Africa, Latin America, and eastern Europe. Risk factors include socioeconomic status, household crowding, ethnicity, migration from high prevalence regions, and infection status of family members. H. pylori infection is not associated with specific symptoms in children; however, it is consistently associated with antral gastritis, although its clinical significance is unclear. Duodenal ulcers associated with H. pylori are seldom seen in children under 10 years of age. H. pylori-infected children demonstrate a chronic, macrophagic, and monocytic inflammatory cell infiltrate and a lack of neutrophils, as compared with the response observed in adults. The effect of H. pylori infection on acid secretion in children remains poorly defined. The events that occur during H. pylori colonization in children should be studied more thoroughly and should include urease activity, motility, chemotaxis, adherence, and downregulation of the host response. The importance of virulence determinants described as relevant for disease during H. pylori infection has not been extensively studied in children. Highly sensitive and specific methods for the detection of H. pylori in children are needed, especially in younger pediatric populations in which colonization is in its early phases. Criteria for the use of eradication treatment in H. pylori-infected children need to be established. Multicenter pediatric studies should focus on the identification of risk factors, which can be used as prognostic indicators for the development of gastroduodenal disease later in life.

When can complete regression of low-grade gastric lymphoma of mucosa-associated lymphoid tissue be predicted after helicobacter pylori eradication?

AIMS

Recent studies suggest that primary low-grade gastric lymphomas of mucosa-associated lymphoid tissue (MALT) are cured in many cases between 1 and 18 months after H. pylori eradication. The aim of this study is to elucidate when complete regression (CR) of MALT lymphoma can be histologically predicted after H. pylori eradication.

METHODS AND RESULTS

Twenty-one patients with low-grade gastric MALT lymphoma were treated with triple therapy (amoxicillin, clarythromycin and proton pump inhibitor) for 14 days. Subsequently, they were followed up by sequential endoscopy and biopsy (number of biopsy specimens for each endoscopy is 3-8, with an average of 4) from 91 to 657 days (average: 309 +/- 165 days). Eradication of H. pylori infection was achieved in all patients. Nine patients were free of lymphoma at 1 to 2 months after eradication and remained in CR at 163-657 days. Twelve patients showed residual lymphoma at 1 to 2 months after eradication. Five out of 12 patients revealed only one or two small foci of lymphoma-cell aggregation and showed a high incidence (80%) of CR at the latest biopsy (135-434 days, average 276 +/- 115 days after eradication), while seven patients showed diffuse remains of lymphoma cells and indicated CR in only one case (14%) at 362 days, partial regression in five cases at 130-431 days (average 227 +/- 114 days), and no change in one case at 91 days after eradication.

CONCLUSIONS

: These results suggest that CR of low-grade MALT lymphoma can be predicted at 1 to 2 months after eradication therapy by checking histological changes of MALT lymphoma cells.

Limitations of clonality analysis of B cell proliferations using CDR3 polymerase chain reaction

BACKGROUND/AIMS

Detection of clonal immunoglobulin heavy chain (IgH) rearrangements by the polymerase chain reaction (PCR) is an attractive alternative to Southern blotting in lymphoma diagnostics. However, the advantages and limitations of PCR in clonality analysis are still not fully appreciated. In this study, clonality was analysed by means of PCR, focusing in particular on the sample size requirements when studying extremely small samples of polyclonal and monoclonal lesions.

MATERIALS/METHODS

High resolution complementarity determining region 3 (CDR3) PCR was used to investigate the minimum number of cells and the amount of tissue required for the detection of a polyclonal population, both for fresh cells and formalin fixed, paraffin wax embedded tissue. Subsequently, frozen and paraffin wax embedded samples of 76 B cell lymphoproliferative disorders, 43 of which were tested by means of Southern blotting, were analysed to establish the sensitivity of this assay. These specimens included 12 chronic lymphocytic leukaemias (CLLs), nine mantle cell lymphomas (MCLs), 10 follicular lymphomas (FLs), and 45 mucosa associated lymphoid tissue (MALT) lymphomas. The specificity was tested on reactive lymph nodes (n = 19), tonsils (n = 4), peripheral blood lymphocyte fractions (n = 4), and biopsies with gastritis (n = 21).

RESULTS

In reactive tissue, 20 ng of high molecular weight DNA derived from 6.5-9 x 10(3) B cells was sufficient to obtain a polyclonal PCR result. With smaller amounts "pseudoclonality" could be induced. When using paraffin wax blocks, undiluted DNA isolated from tonsillar tissue of at least 1 mm2 was necessary to obtain a polyclonal pattern. The sensitivity required to detect clonality in paraffin wax embedded and frozen tissue by PCR for FL (40% and 60%, respectively) was lower than that for MALT lymphomas (60% and 86%, respectively), CLL (78% and 89%, respectively), and MCL (88% and 100%, respectively). PCR specificity was 96% and 100% for frozen and paraffin wax embedded tissue, respectively.

CONCLUSION

The minimum amount of template for CDR3 PCR is approximately 20 ng of high molecular weight DNA or 1 mm3 of B cell rich paraffin wax embedded normal tonsillar tissue, but care has to be taken to avoid pseudoclonality when low numbers of B cells are present. Duplicate or triplicate tests should be performed to avoid misinterpretation. The specificity of the PCR assay is almost 100%, whereas sensitivity depends on a combination of factors, such as lymphoma type and tissue fixation. Because frozen samples yield better results, obtaining fresh material for the PCR assay is recommended, especially when analysing FL and MALT lymphomas.

Acquired gastric mucosa-associated lymphoid tissue (MALT): a review with special emphasis on association with extragastric diseases and management problems of gastric MALT

Mucosa-associated lymphoid tissue is absent physiologically in normal gastric mucosa, but it can develop in some pathologies (dyspepsia, celiac disease, autoimmune diseases) due to certain (Helicobacter pylori, gluten) or uncertain (viruses?) antigenic stimuli. Its importance is related to the consideration that it is the background for the development of gastric mucosa-associated lymphoid tissue (MALT) lymphoma, and its histologic progression to MALT lymphoma may be diagnosed using Isaacson's score. Monoclonal bands can be diagnosed in acquired gastric MALT as well as in gastric MALT lymphoma, but its role is unknown. To prevent development of MALT lymphoma from acquired MALT, currently anti-H. pylori treatment in all H. pylori- and MALT-positive patients is not suggested--only in patients with grade 3 of acquired MALT--due to the high risk of developing MALT lymphoma in these patients. At the same time, the etiology of gastric MALT in autoimmune extragastric diseases is not clear. Additional studies are needed to clarify this relation and its possible causes.

Gastric MALT lymphoma: from concept to cure

Gastric MALT lymphomas are clinically and histologically quite distinct from comparable low-grade B-cell lymphomas of lymph nodes. Their histology suggests that immunological mechanisms might be operative in their growth. Given that there is normally no lymphoid tissue in gastric mucosa and that Helicobacter pylori (H. pylori), the only common bacterial antigen in the stomach, results in the accumulation of gastric MALT, the possibility that this organism is implicated in the pathogenesis of gastric lymphoma has been extensively investigated. It appears that most, but not necessarily all, gastric MALT lymphomas arise in MALT acquired in response to H. pylori infection and develop by stepwise accumulation of genetic abnormalities. Early molecular events in the evolution of gastric MALT lymphoma from 'acquired' MALT include trisomy 3, t(11;18)(q21;q21), genetic damage leading to genetic instability, as indicated by the so-called replication error repair (RER) phenotype, and both p53 and c-myc mutations. At this stage in their development, the growth of the lymphomas is driven by contact between the neoplastic B cells and H. pylori specific intra-tumoral T cells. Eradication of H. pylori causes the tumour to enter a latent phase resulting in clinical regression. Later events, such as t(1;14)(p22;q32), appear to be linked to a capacity for autonomous growth, loss of sensitivity to H. pylori and dissemination of the lymphoma beyond the stomach and gastric lymph nodes. Cloning of the breakpoint in t(1;14) has allowed the identification of a new tumour suppresser gene, bc110. High grade transformation of MALT lymphoma has been associated with p53 inactivation, deletions of p16 and t(8;14).

Descriptive epidemiology of gastrointestinal non-Hodgkin's lymphoma in a population-based registry

The incidence of non-Hodgkin's lymphoma (NHL), particularly at certain extranodal sites, has been demonstrated to be rising, at least in the USA, more than for any other malignancy. One of the major sites of extranodal NHL is the gastrointestinal tract, though little is known of its epidemiological characteristics. Over an 8-year period (1986 to 1993) 1069 primary gastrointestinal NHL cases were reported to the Leukaemia Research Fund Data Collection Survey which covers many parts of England and Wales. Age-standardized incidence rates of gastrointestinal NHL at all sites (0.58/10(5) per year), gastric (0.24/10(5) per year), small bowel (0.17/10(5) per year) and large bowel (0.06/1(5) per year) confirmed that the UK has the lowest rates of gastrointestinal NHL in Europe. An excess of males was observed at all ages and for all sites. Time-trend analyses showed annual increases in incidence rates for gastric (6.3%) and small bowel (5.9%) NHL although a concomitant decrease in gastrointestinal NHL of unknown site suggested that at least part of these increases had resulted from more accurate diagnoses. Overall, the incidence of gastrointestinal NHL significantly increased by 2.7% per annum and was limited to the population aged over 50 years in this series.

Low prevalence of monoclonal B cells in Helicobacter pylori gastritis patients with duodenal ulcer

We have studied the prevalence of B-cell clonality among a large group of 320 patients with Helicobacter pylori gastritis and duodenal ulcer. These patients underwent endoscopic examination with multiple gastric biopsies at diagnosis and were followed 2 and 12 months after therapy. Histopathologic examination of 809 sets of biopsy specimens showed lymphoid gastritis with lymphoid aggregates or follicles, but without lymphoepithelial lesion, in 302 samples corresponding to initial biopsy specimens (n=130) or to posttreatment biopsy specimens (n=172). DNA extracted from fresh antral specimens allowed the amplification of Helicobacter pylori DNA in all cases before therapy. The arrangement of the immunoglobulin heavy chain gene was studied by polymerase chain reaction (PCR) in the 302 selected lymphoid gastritis samples. Single or dominant bands were seen only in four specimens from three patients (1.3%), whereas a polyclonal pattern was seen in the other 298 samples. The detection threshold of our PCR technique was approximately 3% of clonal B cells diluted in a polyclonal population. This threshold appeared to be a reliable cutoff between polyclonal gastritis and clonal MALT lymphoma. In our experience, Helicobacter pylori lymphoid gastritis appeared mainly as a benign polyclonal condition.

Gastric low-grade mucosa-associated lymphoid tissue lymphomas: their histogenesis and high-grade transformation

Gastric low-grade mucosa-associated lymphoid tissue (MALT) lymphoma is a unique disease. A vast majority of lymphoma cells are centrocyte-like cells or resemble monocytoid B cells, and occasionally show plasmacytic differentiation. Immunophenotypical and immunogenotypical examinations have indicated that they are in the differentiation stage of memory B cells, whose normal counterparts are marginal zone lymphocytes or monocytoid B cells in the lymphoid tissues. It arises from chronic gastritis closely associated with Helicobacter pylori (H. pylori) infection. Mucosa-associated lymphoid tissue lymphomas of other organs are also based on acquired MALT associated with chronic inflammation or autoimmune diseases. Interestingly, the majority of gastric low-grade MALT lymphomas regress by the eradication of H. pylori. The lymphoma cells, however, are not derived from B cells reacting with H. pylori itself but from autoreactive B cells. Although the mechanism of their oncogenesis has not been clarified, previous data suggest that autoreactive B cells proliferate in response to H. pylori-specific T cells, presumably with some cytokines. The genetic instability of such B cells then induces chromosomal abnormalities including trisomy 3 and/or other genetic changes. These B cells have the ability of autonomic proliferation and, even so, they might be sensitive to T cell stimuli. Low-grade gastric lymphomas occasionally progress to high-grade malignancy. The high-grade component of MALT lymphomas are composed of large-sized lymphoma cells that are morphologically indistinguishable from nodal large B cell lymphomas. This high-grade transformation is associated with p53 abnormalities or Bcl-6 overexpression. Gastric MALT lymphoma may provide a useful model in understanding multistep lymphomagenesis.

B-cell monoclonality precedes the development of gastric MALT lymphoma in Helicobacter pylori-associated chronic gastritis

Little is known about the temporal changes in Helicobacter pylori density and B-cell clonality during the evolution from chronic gastritis to gastric mucosa-associated lymphoid tissue (MALT) lymphoma. Biopsied specimens from 28 patients with chronic gastritis who developed gastric MALT lymphoma (group A) and from 24 similar patients who did not (group B) during an equivalent follow-up period (mean, 42 months) were retrospectively scored for histological features of MALT lymphoma (0 to 5) and H. pylori density (0 to 3). B-cell clonality was analyzed by polymerase chain reaction (PCR). During the observation period, the H. pylori density in group A decreased significantly in comparison with group B; the mean change in H. pylori density (final minus initial density) per 1000 days was -1.4 for group A and +0.2 for group B (P < 0.005). Monoclonality was detected more frequently in group A (79%) than in group B (21%; P < 0.005), and it preceded the histological evidence of malignant transformation in 64% of those patients who showed monoclonality in group A. These results suggest that H. pylori is thus more closely associated with the precursor or initial phase in the genesis of gastric MALT lymphoma than with the later phase, as its density decreases as the tumor progresses. The detection of B-cell monoclonality by PCR is thus of possible use for predicting the histological genesis of gastric lymphoma.

Gastric B-cell clonal expansion and Helicobacter pylori infection in patients with autoimmune diseases and with dyspepsia. A follow-up study

BACKGROUND

It is not clear whether gastric B-cell clonal expansion, a possible precursor of mucosa-associated lymphatic tissue (MALT) lymphoma, is exclusively linked to Helicobacter pylori infection and virulence.

METHODS

In this study we followed up, for up to 33 months, 16 VDJ polymerase chain reaction-positive patients (4 with dyspepsia, 9 with Sjögren's syndrome, and 3 with other autoimmune diseases). Of these, 12 were H. pylori-positive. In addition, in H. pylori-positive patients we tested whether the serum anti-cag-A (a potential marker of virulence) was preferentially associated with B-cell clonality.

RESULTS

In all but one patient clonality appeared temporally unrelated to H. pylori infection. The prevalence of anti-cagA was not higher in H. pylori/VDJ-positive patients than in controls.

CONCLUSIONS

These data indicate that, in addition to H. pylori, gastric B-cell clonality may be sustained by other agents/mechanisms. Anti-cag-A does not appear to be involved in the pathogenesis of clonality.

Characterization of prelymphomatous stages of B cell lymphoproliferation in Sjögren's syndrome

OBJECTIVE

To determine whether the prelymphomatous stages of B cell lymphoproliferation in Sjögren's syndrome (SS) may be better characterized by the integration of clinical, pathologic, and molecular data, the latter focusing on the expansion, persistence, and dissemination of clonal B cells in the course of the disease.

METHODS

Multiple tissue lesions (synchronous from different tissues and metachronous from the same tissue) were evaluated in biopsy specimens obtained from 6 consecutive patients with SS who had an associated lymphoproliferative disorder. Fully benign gastric lesions were evaluated in tissue from an additional 11 patients with SS who had no associated lymphoproliferative disorder. Multiple and complementary molecular analyses of B cell clonality were used: Southern blot, polymerase chain reaction, single-strand conformation polymorphism, DNA sequencing, and hybridization with clonospecific oligoprobes. All the patients were then strictly followed up for the appearance of lymphoma.

RESULTS

Different scenarios of SS-associated B cell lymphoproliferation were identified: 1) the ongoing expansion of the same dominant clone, localized or disseminated, in tissue from 2 patients, 1 of whom later developed an overt B cell lymphoma; 2) different dominant clones in different synchronous or metachronous tissues from the remaining 4 patients with an associated lymphoproliferative disorder; and 3) small oligoclonal expansions in 7 of the 11 benign gastric lymphoid infiltrates.

CONCLUSION

Prelymphomatous B cell lymphoproliferation in SS was better characterized following integration of the findings. The different types of B cell clonal expansion (oligoclonal or monoclonal, smaller or larger in size, fluctuating or established, localized or disseminated) may imply a different risk of lymphoma progression. An accurate clinical, histopathologic, and molecular characterization may therefore be crucial in future studies aimed at clarifying the pathobiology of SS-associated lymphoproliferation.