Regression of primary gastric lymphoma of mucosa-associated lymphoid tissue type after cure of Helicobacter pylori infection. MALT Lymphoma Study Group

13C-urea breath test in Helicobacter pylori diagnosis and eradication. Correlation to histology, origin of 'false' results, and influence of food intake

BACKGROUND

Which protocol is optimal for the 13C-urea breath test (UBT) for Helicobacter pylori detection is controversial. This study aimed to characterize a very simple UBT protocol for the clinical routine (two-point-analysis performed with 75 mg 13C-urea and citric acid) with special consideration of 'false' UBT results. RESULTS; UBT was evaluated in reference to histology (Warthin-Starry). In mismatching results re-gastroscopy was performed. By UBT, 74 of 77 patients with H. pylori-positive histology were detected (sensitivity, 96%). The false-negative UBTs were due to low colonization densities during spontaneous H. pylori elimination or pyloric obstruction. Seven of 49 patients with negative histology had a positive UBT, but re-gastroscopy showed that all of them had a positive histology when multiple antral biopsy specimens were taken (UBT specificity, 100%). UBT correlated only weakly with H. pylori colonization density. No correlation was found between UBT and gastric neutrophil and lymphocyte infiltration. UBT reproducibility was excellent (93 of 94 in a 6-month period). Non-fasting conditions induced a shift to lower UBT results in H. pylori-positive and to higher UBT results in negative patients, resulting in 2 of 10 false-positive and 1 of 10 false-negative UBTs.

CONCLUSION

This simple version of the urea breath test combines the highest sensitivity with excellent reproducibility. It is superior to histologic detection of H. pylori in the clinical routine and an optimal tool for monitoring H. pylori eradication. Fasting conditions are required for the test.

Circulating villous lymphocytes--a link between hyperreactive malarial splenomegaly and splenic lymphoma

Significant numbers of villous lymphocytes were noted in the blood of patients with a clinical diagnosis of hyperreactive malarial splenomegaly (HMS) in Ghana. Demographic and haematological data were recorded from 22 patients with massive splenomegaly. Additional investigations included lymphocyte immunophenotyping, protein electrophoresis and immunoglobulin gene rearrangements. Although all patients had over 30% villous lymphocytes and no leucocytosis, 7 had no evidence of a monoclonal disorder. Immunophenotyping and the presence of monoclonal lymphocytes identified 3 further patients with B-cell splenic lymphoma with villous lymphocytes (B-SLVL). HMS and SLVL co-existed in the same, predominantly female, patient population and were indistinguishable except by molecular analysis of lymphocytes. The discovery of the uncommon villous lymphocytes in both non-malignant and malignant disorders in the same geographical area suggested that HMS and SLVL are pathophysiologically related. In Caucasians with SLVL the malignant cells arise from B-cells that have undergone antigen selection. We postulate that the excessive proliferation of polyclonal B-lymphocytes, driven by frequent exposure to malaria, predisposes to the emergence of a malignant lymphoma, B-SLVL, in tropical West Africa.

The growth of primary low-grade B-cell gastric lymphoma is sustained by Helicobacter pylori

BACKGROUND

The growth of primary low-grade B-cell gastric mucosa-associated lymphoid tissue (MALT) lymphoma is an antigen-dependent process

CASE

We were able to document the influence of Helicobacter pylori on the natural history of primary low-grade B-cell gastric MALT lymphoma in a case investigated by means of polymerase chain reaction for IgH rearrangement. In this case the presence or absence of the bacterium appeared to affect both clinical manifestations and histologic features of the neoplasia, with an acceleration or a slowing down of the neoplastic expansion, respectively.

CONCLUSIONS

We identified H. pylori as an antigenic stimulus that supports the growth of MALT-type lymphoma. This finding enables us to make some considerations about the management of the disease.

Borrelia burgdorferi-associated primary cutaneous B cell lymphoma: complete clearing of skin lesions after antibiotic pulse therapy or intralesional injection of interferon alfa-2a

We report two patients with low-grade malignant primary cutaneous B cell lymphoma in association with Borrelia burgdorferi infection. Extracutaneous manifestations were ruled out by standard staging procedures. Infection with Borrelia burgdorferi was confirmed by cultivation from lesional skin in both patients. In the first patient skin lesions cleared completely after pulse therapy with cefotaxime, whereas in the second patient antibiotic treatment failed. In this patient, however, skin lesions completely cleared after intralesional injection of interferon alfa-2a. Antibiotic treatment or intralesional injection of interferon alfa-2a should be considered as a first-line treatment of Borrelia burgdorferi-associated primary cutaneous B cell lymphoma before more aggressive conventional therapeutic modalities (e.g., radiation therapy) are applied.

Regression of a large gastric MALT lymphoma with antibiotic treatment to eradicate Helicobacter pylori

We report a case of a large low-grade gastric lymphoma of mucosa-associated lymphoid tissue (MALT), which regressed following the eradication of concurrent Helicobacter pylori infection. This case lends further support to a policy of H pylori eradication as a first line therapy for all these lesions, irrespective of size. The long-term prognosis of tumours treated in this way, however, needs further evaluation.

Gastric lymphomas compared with lymph node lymphomas in a population-based registry differ in stage distribution and dissemination patterns but not in patient survival

BACKGROUND

Non-Hodgkin's lymphoma (NHL) originating in mucosa-associated lymphoid tissue (MALT) is supposed to have different clinical behavior from lymph node NHL. To test this hypothesis, the authors compared data of gastric NHL patients with lymph node NHL patients in a population-based registry for differences in clinical presentation and prognosis.

METHODS

Data from 1981-1989 on patients with primary gastric NHL (n = 109) and patients with primary lymph node NHL (n = 658) were retrieved from a Dutch population-based NHL registry. Patients were compared for stage distribution, involved sites, and survival. The prognostic value of grading lymphomas according to the malignancy grades of the Working Formulation for Clinical Usage was compared with the value of grading MALT NHLs as either low grade or high grade malignancies.

RESULTS

Patients with gastric NHL presented more often with localized disease. Stage IV patients had a higher rate of dissemination to other non-lymph node sites but less frequent localization in the bone marrow. The restricted pattern of dissemination was reflected in a significantly lower recurrence rate for gastric NHL. Gastric NHL patients had significantly better disease free survival than lymph node NHL patients (80% and 44% at 5 years, respectively; P < 0.001). In contrast, overall survival did not significantly differ between the two groups, and it appeared to depend on disease stage. Grading MALT lymphoma as either low grade (26%) or high grade (70%) malignancies did not provide better prognostic information than grading according to the Working Formulation for Clinical Usage (low 8%, intermediate 75%, high 9%).

CONCLUSIONS

Primary gastric NHL shows a restricted dissemination pattern, which gives support to the MALT lymphoma concept. Although this might explain the superior disease free survival observed for gastric NHL patients, it does not translate into better overall survival for these patients.

Gut lymphomas

Gut lymphoma still remains the subject of much debate and controversy with respect to pathological classification, clinical staging and treatment. This is mainly due to the fact that most studies reported retrospective non-randomized evaluations of small series and lacked uniformity in histological classification, patients' characteristics and type of treatment. Moreover, most of the historical series were published before the recognition of MALT as the origin of most GI lymphomas. Hence, there is a compelling need for the use of modern histological criteria for primary GI lymphomas because of their unique histology, special features and origin in mucosal tissue. General adoption of the histological classification proposed in 1988 by Isaacson et al (Table 1) can be recommended which follows the general principles of the Kiel Classification and includes the MALT lymphomas as a particular disease entity. Combination chemotherapy is the treatment of choice for gut lymphomas with aggressive histology and multiple node involvement or disseminated disease. The effectiveness of combination chemotherapy in advanced disease has excited a reconsideration of the role of primary surgery in less advanced cases where surgery has, historically, been the initial procedure of choice. This is particularly true for gastric lymphomas where it is possible that, in future, surgery will be resorted to as a potential approach for salvage when complete remission is not achieved with conservative therapy. For primary intestinal lymphoma, however, there are as yet no studies which clearly demonstrate that surgery is not necessary. With respect to the group of localized low-grade MALT lymphomas of the stomach and the indolent nature of the disease make plausible a conservative approach, with antibiotic eradication of H. pylori as the sole initial treatment. This may avert or at least postpone the indication for surgical resection in the majority of patients.

Primary gastric non-Hodgkin's lymphoma stage IE and IIE

The aim of this study was to evaluate retrospectively the different treatment approaches and outcome of patients with stage IE and IIE gastric non-Hodgkin's lymphoma in a cancer registry. Between 1982 and 1992, the Comprehensive Cancer Centre South (CCCS), Eastern Section, The Netherlands, registered, in a population of 1 million people, a total of 81 cases of gastric lymphoma stage IE and IIE (43 men and 38 women). Median age was 69.7 years (range 30.4-88.1). According to the Working Formulation, the malignancy grade was: 9 low, 55 intermediate and 14 high. According to the MALT classification, the malignancy grade was: 38 low and 40 high. Grade was unknown in 3 patients. Patients received the following treatment modalities: surgery alone (n = 22), locoregional radiotherapy without (n = 12) or with (n = 13) surgery; or systemic chemotherapy alone (n = 10) or with radiotherapy and/or surgery (n = 18). No treatment was given or recorded in 6 patients. For stage IE, 5-year actuarial survival and relapse-free survival rates were, respectively, 76 and 64% in 18 patients who received only surgery; 70 and 67% in 17 patients given locoregional treatment (radiotherapy with or without surgery), and 76 and 62% in 13 patients given systemic treatment (chemotherapy alone or with radiotherapy and/or surgery). Radiotherapy as sole treatment seemed to be as effective as other treatment modalities in achieving local and abdominal control. For stage IIE, none of the 4 patients who were treated with surgery alone survived 5 years. The 5-year actuarial survival and relapse-free survival rates of 8 patients who received radiotherapy with or without surgery were, respectively, 25 and 17% and 49 and 33%, for 14 patients given systemic therapy (chemotherapy alone and/or radiotherapy/surgery). In stage IIE, local, abdominal as well as distant relapse were more common, irrespective of treatment modality. In the multivariate analyses, stage (P = 0.002), grade (P = 0.02), age (P = 0.04) and gender (P = 0.04) were significant prognostic factors. This report on a limited number of patients shows that the outcome of patients with stage IIE gastric lymphoma is much worse than for patients with stage IE. Grade, age, gender and particularly stage are much stronger indicators for survival than different modes of treatment. Systemic therapy might improve outcome for stage IIE, but not for stage IE, for which radiotherapy alone seems a good option.

Biased VH family usage in primary gastric B cell lymphoma of mucosa-associated lymphoid tissue-type and the selected V beta expression of T cells infiltrating into the lymphoma cells

Seven cases of primary gastric low-grade B cell lymphoma of mucosa-associated lymphoid tissue (MALT) type, two cases of high-grade B cell lymphoma with a low-grade component and three cases of pure high-grade lymphoma were selected for the current study. The Ig VH gene use of lymphoma cells and the V beta repertoires of infiltrating T cells were investigated. The VH gene analysis showed multiple VH family usage in 12 cases, but the MALT-type lymphoma cell usage was found to be biased for the families that have a low number of VH genes (VHIV and V). Another analysis of lymphoma-infiltrating T cells showed restricted expressions of the V beta repertoire in all seven low-grade cases and three high-grade cases. In those 10 cases, a considerable number of CD4-positive T cells infiltrated into lymphoma cells and RAG-1 was also prominently expressed. Based on these findings, it was thus assumed that the normal counterpart of gastric B cell lymphoma of MALT type is different from the conventional B cell lymphoma, and the restricted expression of V beta repertoires is therefore considered to be a characteristic finding in low-grade B cell lymphomas of MALT type as well as in a proportion of high-grade lymphomas (the so called 'high-grade lymphoma of MALT type').

Identification of a 23S rRNA gene mutation in clarithromycin-resistant Helicobacter pylori

BACKGROUND

Transition mutations (A-G) at residue 2143, cognate to position 2058 in the Escherichia coli 23S rRNA gene, have been shown to confer resistance to macrolides in Helicobacter pylori. This study reports the finding that transversion mutations (A-C) can occur at 2143 as well.

MATERIALS AND METHODS

Three clarithromycin-resistant H. pylori isolated from three different patients after treatment with clarithromycin were analyzed for point mutations by cycle sequencing of a 163-bp amplified region surrounding residue 2143 within the conserved loop of the 23S rRNA gene.

RESULTS

Nucleotide sequence comparisons of a 163-bp amplified product revealed that A-C transversion mutations occurred at position 2143. H. pylori isolated from the patients prior to treatment were susceptible to clarithromycin and displayed no polymorphism at 2143.

CONCLUSION

This is the first report to show that A-C transversion mutations at position 2143 can confer resistance to clarithromycin in H. pylori and further support the role that mutations at position 2143 play in conferring macrolide resistance in H. pylori.

Gastric lymphoma causing gastric outlet obstruction

An unusual presentation of abdominal lymphoma causing gastric outlet obstruction is reported. Gastric lymphoma should be considered in the differential diagnosis of gastric outlet obstruction during childhood. The possibility of gastric malignancy should not be excluded only on the basis of the patient's age. Complete resection of the tumor, with postoperative radiation and/or chemotherapy is the best method of treatment for high-grade lymphomas.

Primary non-Hodgkin lymphoma of the stomach: endoscopic pattern and prognosis in low versus high grade malignancy in relation to the MALT concept

BACKGROUND

Various histological classifications developed for nodal lymphomas failed to be of value in extranodal lymphomas. More recently, gastric lymphoma is considered to represent a distinctive group derived from mucosa associated lymphoid tissue (MALT).

AIM

To study the prognostic value of malignancy grading based on the concept that most gastric lymphomas are of MALT origin, the endoscopic as well as clinical characteristics in 114 patients with primary gastric non-Hodgkin's lymphoma were evaluated.

RESULTS

In univariate analysis, patients with low grade lymphoma (n = 51) were younger, had less advanced stage, and less frequently bulky disease than those with high grade lymphoma (n = 63). In multivariate analysis weight loss and increased erythrocyte sedimentation rate were significantly less frequent in low grade (45% and 22%) compared with high grade lymphoma (75% and 53%). In low grade lymphoma endoscopic findings were often interpreted as a benign condition (27 of 51), in contrast with high grade lymphoma, where carcinoma was most frequently (37 of 63) suspected. In low grade lymphoma complete remission rate was 92%, and five year survival 75%, In high grade lymphoma results were significantly less favourable (p = 0.0001): complete remission in 68%, and a five year survival of 46%.

CONCLUSION

Malignancy grading was strongly correlated with treatment outcome; endoscopically low grade lymphoma was often hard to distinguish from benign conditions, whereas high grade lymphoma often revealed carcinoma-like features.

Depth of infiltration of primary gastric B-cell lymphomas--correlations with proliferation, apoptosis and expression of p53 and bcl-2

Local extension has been shown to be a major prognostic factor in primary gastric B-cell lymphoma. In order to evaluate whether this parameter might be correlated with cell proliferation or its regulation, a retrospective study was performed. Fifty-three surgical specimens with primary gastric B-cell lymphomas were analysed concerning histological grading, depth of infiltration and Ann-Arbor stage. In addition, immunohistochemistry (p53[Do7], bcl-2[bcl-2-124], Ki-67 [MiB1]) and in situ end-labeling (apoptotic bodies) were applied. The depth of infiltration was significantly correlated with Ann-Arbor stage (p < 0.001) and histological grading (p < 0.002). Furthermore, the semiquantitatively evaluated expressions of Ki-67, apoptotic bodies and p53 revealed that tumours limited to the mucosa and submucosa had lower numbers of stained cells than lymphomas infiltrating the muscularis propria or beyond (p < 0.001 in all cases). Analysis of bcl-2 expression showed an inverse picture (p < 0.05). The importance of local spread of gastric lymphomas is underscored by our findings: in gastric lymphomas infiltrating the muscularis propria or beyond, powerful proliferative stimuli have been acquired, e.g. associated with p53 mutations, that are independent of the known mucosa-associated stimuli, Helicobacter pylori and auto-immunity.

Population genetic analysis of Helicobacter pylori by multilocus enzyme electrophoresis: extensive allelic diversity and recombinational population structure

Genetic diversity and relationships in 74 Helicobacter pylori isolates recovered from patients assigned to distinct clinical categories were estimated by examination of allelic variation in six genes encoding metabolic housekeeping enzymes by multilocus enzyme electrophoresis. Seventy-three distinct allele profiles, representing multilocus chromosomal genotypes, were identified. All six loci were highly polymorphic, with an average of 11.2 alleles per locus. The mean genetic diversity in the sample was 0.735, a value that exceeds the level of diversity recorded in virtually all bacterial species studied by multilocus enzyme electrophoresis. A high frequency of occurrence of null alleles (lack of enzyme activity) was identified and warrants further investigation at the molecular level. Lack of linkage disequilibrium (nonrandom association (of alleles over loci) indicates that horizontal transfer and recombination of metabolic enzyme genes have contributed to the generation of chromosomal diversity in H. pylori. In this sample of isolates, there was no statistically significant association of multilocus enzyme electrophoretic types or cluster of related chromosomal types and disease category.

Chronic proliferative hepatitis in A/JCr mice associated with persistent Helicobacter hepaticus infection: a model of helicobacter-induced carcinogenesis

Helicobacter hepaticus causes hepatitis in selected strains of mice and in A/JCr mice is linked to liver cancer. To analyze whether H. hepaticus persists in specified ecological niches, to determine whether biomarkers of infection exist, and to analyze the influence of H. hepaticus on hepatocyte proliferation, a longitudinal study of H. hepaticus-infected A/JCr mice was undertaken. A/JCr mice were serially euthanatized from 3 through 18 months and surveyed by enzyme-linked immunosorbent assay; bacterial culture of liver, colon, and cecum; histology; electron microscopy; hepatocyte proliferation indices determined by using 5-bromo-2'-deoxyuridine; and measurement of the liver enzyme alanine aminotransferase. In infected animals throughout the 18-month study, H. hepaticus was consistently isolated from the lower bowel but only sporadically from the liver. By electron microscopy, H. hepaticus was noted infrequently and only in bile canaliculi. Infected mice, particularly males, showed chronic inflammation; oval cell, Kupffer cell, and Ito cell hyperplasia; hepatocytomegaly; and bile duct proliferation. The inflammatory and necrotizing lesion was progressive and involved the hepatic parenchyma, portal triads, and intralobular venules. Hepatic adenomas were noted only in male mice, whereas 5-bromo-2'-deoxyuridine proliferation indices were markedly increased in both sexes, but especially in males, compared to control A/J mice. Infected mice also developed sustained anti-H. hepaticus serum immunoglobulin G antibody responses and elevated alanine aminotransferase levels. H. hepaticus, which persists in the lower bowels and livers of A/JCr mice, is associated with a chronic proliferative hepatitis, and hepatomas in selected male mice indicate that this novel bacterium may cause an increased risk of hepatic cancer induction in susceptible strains of mice. This murine model should prove useful in dissecting the molecular events operable in the development of neoplasms induced by bacteria belonging to this expanding genera of pathogenic Helicobacter species.

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

BACKGROUND

Although Helicobacter pylori has been implicated in the pathogenesis of gastric mucosa associated lymphoid tissue (MALT) and MALT lymphoma, it is not known how it may trigger these lesions and whether there is an identifiable pre-neoplastic stage.

AIMS

To investigate the relation between MALT, H pylori infection, and B-cell clonality (a potential marker of pre-neoplastic lesions).

PATIENTS

141 subjects with simple dyspepsia.

METHODS

Gastric biopsy specimens from all patients were examined for MALT and H pylori. Of these, 25 consecutive MALT positive specimens were scored for features of MALT lymphoma and VDJ clonality studied by polymerase chain reaction.

RESULTS

Overall, prevalence was 62% for H pylori and 46% for MALT. VDJ clonality was frequent in the sub-group studied (nine of 25), mostly associated with lymphoid follicles (eight of nine or 89%), and with a high scoring for MALT lymphoma. VDJ clonality was equally frequent in patients with and without H pylori (seven of 20 and two of five or 35% and 40% respectively).

CONCLUSIONS

B-cell clonality is unexpectedly common in subjects with simple dyspepsia and MALT raising clinical management questions. These findings also suggest that the cascade MALT formation--B-cell clonality--MALT lymphoma may not be uniquely associated with H pylori infection.

Atypical lymphoid infiltrations of the gastric mucosa--their interpretation and management by eradication of Helicobacter pylori

Low-grade gastric lymphomas of mucosa-associated lymphoid tissue (MALT) may be extremely difficult to differentiate from atypical lymphoid infiltrations of the gastric mucosa caused by Helicobacter pylori (H. pylori) infection, especially if lympho-epithelial destructions are not detected. In order to clarify this diagnostic problem and to evaluate the potential benefit of clearing H. pylori-induced lymphoid infiltration a prospective study was performed. Our study included biopsy specimens from 61 patients, that showed excessive lymphoid infiltrations. Using histology and immunohistochemistry no definite diagnosis could be delivered. In 46 (76.4%) cases histological regression occurred 4 weeks after the end of therapy suggesting a reactive infiltrate. In 7 patients (11.5%) the histological picture remained unchanged, and in 8 (13.1%) the follow-up biopsies revealed lympho-epithelial destructions allowing the diagnosis of low-grade MALT lymphoma. On the basis of our data we conclude that eradication of H. pylori could provide an additional tool in the differential diagnosis between atypical lymphoid infiltrations of the gastric mucosa caused by H. pylori and an early primary gastric MALT lymphoma.

Epidemiology of gastric non-Hodgkin's lymphoma patients: parallels with Helicobacter pylori

BACKGROUND

The incidence of gastric non-Hodgkin's lymphoma (NHL) is increasing in the United States. However, little is known about the etiology of the disease. Some studies have shown an association between gastric NHL and Helicobacter pylori. No study has specifically delineated demographic features that distinguish gastric NHL patients from nongastric NHL patients.

MATERIALS AND METHODS

To obtain information about the differences between gastric and nongastric NHL patients, we conducted a hospital chart review study. We examined charts of all 25 cases of primary gastric NHL, as well as charts of 75 randomly selected nongastric NHL patients as controls. All patients were seen in the Division of Oncology at Stanford University Medical Center from 1972 to 1991. Demographic information was tabulated, and differences between the cases and controls were noted. The identified risk factors were determined by both univariate and logistic regression analyses.

RESULTS

There was no difference between gastric NHL cases and nongastric controls with respect to age, gender, race, and family history of any cancer. However, in logistical regression, persons with gastric NHL were more likely than those with other forms of NHL to be born outside the United States (odds ratio = 12.8; 95% confidence interval = 2.9-56.0) and also to have a family history of stomach cancer (odds ratio = 18.4; 95% confidence interval 2.1-160.1).

CONCLUSIONS

Gastric NHL is more likely than NHL at other sites to occur in persons with a family history of gastric cancer or in those born in developing countries. This epidemiological pattern supports the identified role of H. pylori in the development of gastric lymphoma.

B cell clonality in gastric lymphoid tissues of patients with Sjögren's syndrome

OBJECTIVE

To determine the prevalence of mucosa associated lymphoid tissue (MALT) in the stomach and of a possible antigen driven proliferation, in patients with Sjögren's syndrome (SS).

METHODS

Twenty one patients with primary SS and 80 dyspeptic controls underwent upper endoscopy. Lymphoid tissue and Helicobacter pylori were assessed by histopathological analysis. Epstein-Barr virus (EBV) or human herpes virus-6 (HHV-6) genome were studied by polymerase chain reaction (PCR) DNA amplification. Two PCR VDJ procedures were used to detect immunoglobulin heavy chain (IgH) gene rearrangement.

RESULTS

Organised MALT was found in 33.3% of the patients, compared with 21.5% of the controls (NS). H pylori infection was seen in 71% of patients and 63% of controls. Genomic EBV or HHV-6 was found in a minor portion of SS gastric tissues. B cell expansion was detected in nine of the 21 patients. Infectious agents in the stomach might have contributed to B cell clonality only in 55.5% of the cases. No strict relationship was found between lymphoid follicles and clonality.

CONCLUSION

Lymphoid accumulation in the gastric mucosa is common in Sjögren's syndrome, but full evidence for an antigen driven B cell expansion could not be demonstrated. Only a portion of those with clonal B cell expansion had evidence of an infectious agent. Other unknown infectious agents or factors related to the underlying disease (autoantigen) and its tissue environment may have a further role as possible causes of B clonal expansion in the gastric mucosa.

Chronic proliferative hepatitis in A/JCr mice associated with persistent Helicobacter hepaticus infection: a model of helicobacter-induced carcinogenesis

Helicobacter hepaticus causes hepatitis in selected strains of mice and in A/JCr mice is linked to liver cancer. To analyze whether H. hepaticus persists in specified ecological niches, to determine whether biomarkers of infection exist, and to analyze the influence of H. hepaticus on hepatocyte proliferation, a longitudinal study of H. hepaticus-infected A/JCr mice was undertaken. A/JCr mice were serially euthanatized from 3 through 18 months and surveyed by enzyme-linked immunosorbent assay; bacterial culture of liver, colon, and cecum; histology; electron microscopy; hepatocyte proliferation indices determined by using 5-bromo-2'-deoxyuridine; and measurement of the liver enzyme alanine aminotransferase. In infected animals throughout the 18-month study, H. hepaticus was consistently isolated from the lower bowel but only sporadically from the liver. By electron microscopy, H. hepaticus was noted infrequently and only in bile canaliculi. Infected mice, particularly males, showed chronic inflammation; oval cell, Kupffer cell, and Ito cell hyperplasia; hepatocytomegaly; and bile duct proliferation. The inflammatory and necrotizing lesion was progressive and involved the hepatic parenchyma, portal triads, and intralobular venules. Hepatic adenomas were noted only in male mice, whereas 5-bromo-2'-deoxyuridine proliferation indices were markedly increased in both sexes, but especially in males, compared to control A/J mice. Infected mice also developed sustained anti-H. hepaticus serum immunoglobulin G antibody responses and elevated alanine aminotransferase levels. H. hepaticus, which persists in the lower bowels and livers of A/JCr mice, is associated with a chronic proliferative hepatitis, and hepatomas in selected male mice indicate that this novel bacterium may cause an increased risk of hepatic cancer induction in susceptible strains of mice. This murine model should prove useful in dissecting the molecular events operable in the development of neoplasms induced by bacteria belonging to this expanding genera of pathogenic Helicobacter species.

Helicobacter pylori infection and its role in human disease--an overview

Helicobacter pylori (H. pylori) is probably the commonest chronic bacterial infection in humans. The bacterium colonizes the gastric epithelium and induces inflammation of the underlying mucosa. The recognition that this infection is the most important acquired factor in the pathogenesis of duodenal and gastric ulcers has transformed the management of these common disorders. Most patients with ulcers can be cured by a 1-week course of anti-H. pylori therapy, thereby removing the need for long-term acid inhibitory therapy. Eradication of the infection involves taking complex combinations of drugs and simpler eradication regimens are required. Recent epidemiological data indicate an association between H. pylori infection and the subsequent development of gastric carcinoma. If this association is established as causal, then widespread eradication of the infection may be indicated. Global eradication of H. pylori will probably rely on prophylactic or therapeutic vaccination and this approach is being actively investigated.

Mutations in 23S rRNA are associated with clarithromycin resistance in Helicobacter pylori

Twelve clarithromycin-resistant Helicobacter pylori isolates (100% of resistant isolates examined) from seven different patients each contained an A-->G transition mutation within a conserved loop of 23S rRNA. A-->G transition mutations at positions cognate with Escherichia coli 23S rRNA positions 2058 and 2059 were identified. Clarithromycin-susceptible H. pylori isolates from 14 different patients displayed no polymorphisms in a conserved loop within domain V of 23S rRNA. The study is the first to report mutations in H. pylori associated with resistance to an antimicrobial agent used in established peptic ulcer treatment regimens.

Purine analogs in marginal-zone lymphomas

In an area of lymphoma classification still being defined, marginal-zone lymphomas have distinctive immunohistochemical and cytogenetic features that distinguish them from mantle-cell and follicular lymphomas. There are three subtypes: the extranodal mucosa-associated lymphoid tissue (MALT) lymphomas, the nodal monocytoid B-cell (MBCL) lymphomas, and the splenic marginal-zone lymphomas. The MALT lymphomas represent the neoplastic counterpart of the gut-associated lymphoid tissue, which extends from the jejunum to the rectum. They arise in sites usually containing no lymphoid tissue, such as the stomach, thyroid, and salivary gland. Gastric MALT lymphomas, the most common, are associated with Helicobacter pylori. The MBCL lymphomas closely resemble MALT lymphomas and unlike other non-Hodgkin's lymphomas are commonly composite. Therapy for these lymphomas may include radiation therapy or surgery when disease is of limited extent. However, gastrectomy for gastric MALT lymphomas is not in favor because of the efficacy of antibiotic regimens that can eliminate H. pylori infection. Splenectomy may be indicated for splenic lymphomas. Purine analogs are promising therapeutic agents because they are specific for lymphoid cells. Also, they may prove useful in indolent cancers such as these, because of their activity against dividing and resting cells. Purine analogs may be considered as second-line therapy after alkylating agents for these lymphomas.

Recent developments in our understanding of gastric lymphomas

The histopathologic features of low-grade primary gastric lymphoma recapitulate the structure of Peyer's patches [mucosa-associated lymphoid tissue (MALT)] rather than that of lymph nodes. Transformation of low-grade MALT lymphoma to high-grade disease is well recognized, and it is likely that most high-grade primary gastric lymphomas evolve from low-grade lymphoma of the MALT type and are therefore derived from the same B-cell lineage. Molecular genetic studies of gastric MALT lymphomas have shown that these lymphomas do not share any of the features common to nodal lymphomas but, instead, exhibit a marked increase in the frequency of trisomy 3. Gastric MALT lymphomas also differ from their nodal counterparts with respect to their clinical behavior, which is remarkably favorable. The histologic features of gastric MALT lymphomas suggest that one explanation for their favorable behavior may be that their growth is influenced by antigen. That lymphoma should arise from gastric mucosa is paradoxical, because there is no lymphoid tissue in normal stomach. However, several studies have shown that lymphoid tissue accumulates in gastric mucosa almost exclusively as a consequence of Helicobacter pylori infection and that this lymphoid tissue has MALT characteristics. These findings suggested that H. pylori might provide the antigenic stimulus for the growth of gastric MALT lymphoma. Further evidence for this was the finding of H. pylori in more than 90% of cases of gastric MALT lymphoma. Subsequently, evidence supporting an etiologic role for the organism has steadily accumulated. The incidence of gastric lymphoma is greater in communities with a high prevalence of H. pylori, and a case control study has shown that gastric lymphoma is more common in patients infected with the organism; moreover, the infection precedes the onset of lymphoma. Laboratory studies have shown that the growth of tumor cells from low-grade gastric lymphomas can be stimulated by H. pylori and that the effect is strain-specific and is mediated by contact-dependent help from H. pylori-specific T cells. Parallel clinical studies have shown that cases of low-grade gastric lymphoma, when confined to the mucosa, may regress after eradication of H. pylori from the patient's stomach. It remains to be shown whether deeply penetrating or high-grade tumors will respond in the same way. Other outstanding questions relate to the optimal interval between eradication of H. pylori and final evaluation of the response and to the expected duration of the response. On the basis of these laboratory experiments and clinical findings, it is possible to suggest a scheme for the pathogenesis of gastric MALT lymphoma.

Helicobacter pylori and gastric neoplasia: evolving concepts

There is evidence that Helicobacter pylori infection is associated with gastric cancer and mucosa-associated lymphoid tissue (MALT) lymphoma and possibly with non-ulcer dyspepsia. Eradication therapy for confirmed H. pylori infection may therefore become mandatory in patients with non-ulcer dyspepsia severe enough to warrant endoscopy and in first-degree relatives of patients with gastric cancer. However, routine treatment of asymptomatic carriers awaits confirmation of the association with cancer.

High incidence of other neoplasms in patients with low-grade gastric MALT lymphoma

BACKGROUND

Low-grade gastric MALT lymphoma is an uncommon tumour for which a close association with chronic Helicobacter pylori infection has been suggested. However, given the rarity of MALT lymphoma of the stomach despite the high prevalence of H. pylori infection, it seems plausible that genetic host factors might play a fundamental role in gastric lymphomagenesis.

PATIENTS AND METHODS

We retrospectively reviewed the medical records of 83 patients with low-grade gastric MALT, all of whom resided in a geographic area (southern Switzerland and northern Italy) where the incidence of gastric tumours appears to be uncommonly high.

RESULTS

One or more additional cancers were observed in 17 of 83 patients (20%, 95% CI 12% to 31%) for a total of 23 tumours. Of these, 5 were diagnosed prior to, 12 concomitantly with, and 7 after the gastric MALT lymphoma. Eleven patients had a single additional solid tumour (13%, 95% CI 7% to 22%); 3 patients had non-Hodgkin's lymphoma and one had Hodgkin's disease. Multiple additional cancers were present in 3 cases. Nine of 83 patients have died and 8 of them of a second cancer.

CONCLUSIONS

Unexpectedly an extraordinarily large number of patients with other malignancies was observed in this series. The reasons for this finding are still unknown, but genetic alterations are speculated to play an important role.