Immunoproliferative small intestinal disease (IPSID): a model for mature B-cell neoplasms

H pylori-Negative MALT-Associated Extranodal Marginal Zone Lymphoma: A Comprehensive Case Report and Literature Review

Extranodal marginal zone B-cell lymphoma (ENMZL) of mucosa-associated lymphoid tissue (MALT), a rare subtype of B-cell lymphoma, is typically associated with Helicobacter pylori (H pylori) infection, especially in gastric cases. However, this article presents 2 unique cases of H pylori-negative colonic ENMZL, challenging the conventional understanding of the disease. The first case involves an 80-year-old male diagnosed with Stage 1E ENMZL in the descending colon, and the second describes a 74-year-old male with sigmoid colon ENMZL. Both cases lacked H pylori infection, adding complexity to their management. Accompanying these case studies is a comprehensive literature review, delving into the epidemiology, pathology, clinical features, diagnosis, and treatment of H pylori-negative ENMZL, with a focus on gastrointestinal involvement. This review highlights the importance of considering H pylori-negative cases in ENMZL diagnosis and management, illustrating the need for further research and individualized treatment approaches in this uncommon lymphoma subtype.

Falsely elevated anti-tissue transglutaminase antibodies in patients with immunoproliferative small intestinal diseases: A case series

Immunoproliferative small intestinal disease (IPSID) is an uncommon disease of the small intestine. There is a similarity in the clinical presentations of enteropathic diseases, including celiac disease, tropical sprue, IPSID, and Whipple's disease. A differentiation between them is based on the use of a highly specific serological test for celiac disease and specific histological characteristics. We found that IgA-anti-tissue transglutaminase antibody (IgA-tTG Ab) is falsely elevated in a subset of patients with IPSID. The levels of IgA-tTG Ab fall with the treatment of IPSID. The healthcare professional should be aware of the conditions that lead to a false-positive anti-tTG Ab. Intestinal mucosal biopsies even in the presence of anti-tTG Ab should be done in endemic regions as they provide an opportunity for making a diagnosis of alternative and uncommon diseases before the diagnosis of celiac disease.

Clinical relevance of molecular aspects in extranodal marginal zone lymphoma: a critical appraisal

Extranodal marginal zone B-cell lymphoma of the mucosa-associated lymphoid tissue (MALT lymphoma) is among the more common types of lymphoma accounting for up to 8% of newly diagnosed lymphoma cases. As opposed to other B-cell lymphomas, however, no predominant genetic hallmark has been defined in MALT lymphoma, but different localizations appear to be affected by different, sometimes distinct changes. Nonetheless, a high proportion of these genetic changes reported in MALT lymphomas dysregulate the pathways leading to NF-kB activation. t(11;18)(q21;q21)/BIRC3::MALT1 appears to be MALT lymphoma specific and is found in 24% of gastric and 40% of pulmonary MALT lymphomas. The translocation is associated with more disseminated disease in gastric MALT lymphoma and is found in a large percentage of patients whose lymphoma is unresponsive to antibiotic eradication of Helicobacter pylori. In addition to t(11;18)(q21;q21), nuclear expression of BCL10 or NF-kB appears to be highly associated with lymphoma cell survival independence of H. pylori-mediated stimulations. Antibiotic eradication, however, is the recommended therapy of choice irrespective of genetic findings, and molecular analysis is not required before initiation of therapy. The influence of genetic translocations including t(11;18)(q21;q21) on systemic therapies, however, is less clearly defined. While small series have shown no influence on the outcome for treatment with the anti-CD20 antibody rituximab (R) or treatment with cladribine (2-CdA), conflicting data have been reported for alkylating agents, especially chlorambucil and the combination of R + chlorambucil. None of other genetic changes seen in MALT lymphoma to date has discernible value in routine clinical applications, but recent data suggest that changes in TNFAIP3(A20), KMTD2 and CARD11 might be associated with response to Bruton kinase inhibitors.

Intestinal Mucosa-Associated Lymphoid Tissue Lymphoma Transforming into Diffuse Large B-Cell Lymphoma in a Young Adult Patient with Neurofibromatosis Type 1: A Case Report

Background: Neurofibromatosis type 1 (NF1) is a hereditary cancer syndrome characterized by multiple café-au-lait macules on the skin. Lymphoproliferative malignancies associated with NF1 are limited, although the most common are brain tumors. Case presentation: A 22-year-old woman with NF1 was admitted due to abdominal pain and bloody diarrhea. Her laboratory data exhibited macrocytic anemia and elevated IgA levels. Image studies showed diffuse increased wall thickening in the transverse and descending colon without lymphadenopathy and hepatosplenomegaly. A colonoscopy revealed a hemorrhagic ulcerated mass. Pathological analysis of the tumor tissues confirmed IgA-expressing mucosa-associated lymphoid tissue (MALT) lymphoma with histological transformation. Moreover, whole-exome sequencing in tumor tissues and peripheral blood mononuclear cells identified a somatic frameshift mutation of the A20 gene, which represents the loss of function. The patient responded well to R-CHOP chemotherapy, but the disease relapsed after 1 year, resulting in a lethal outcome. Conclusions: MALT lymphoma in children and young adults is extremely rare and is possibly caused by acquired genetic changes. This case suggests a novel association between hereditary cancer syndrome and early-onset MALT lymphoma.

Nomenclature and diagnosis of seronegative coeliac disease and chronic non-coeliac enteropathies in adults: the Paris consensus

OBJECTIVE

Differential diagnosis of villous atrophy (VA) without coeliac antibodies in adults includes seronegative coeliac disease (CD) and chronic enteropathies unrelated to gluten, ie. non-coeliac enteropathies (NCEs). There is currently no international consensus on the nomenclature and diagnostic criteria for these enteropathies. In this work, a Delphi process was conducted to address this diagnostic and clinical uncertainty.

DESIGN

An international task force of 13 gastroenterologists from six countries was recruited at the 16th International Coeliac Disease Symposium, Paris, 2019. Between September 2019 and July 2021, a Delphi process was conducted through mail surveys to reach a consensus on which conditions to consider in the differential diagnosis of VA with negative coeliac serology and the clinical diagnostic approaches required for these conditions. A 70% agreement threshold was adopted.

RESULTS

Chronic enteropathies characterised by VA and negative coeliac serology can be attributed to two main clinical scenarios: forms of CD presenting with negative serology, which also include seronegative CD and CD associated with IgA deficiency, and NCEs, with the latter recognising different underlying aetiologies. A consensus was reached on the diagnostic criteria for NCEs assisting clinicians in differentiating NCEs from seronegative CD. Although in adults seronegative CD is the most common aetiology in patients with VA and negative serology, discriminating between seronegative CD and NCEs is key to avoid unnecessary lifelong gluten-free diet, treat disease-specific morbidity and contrast poor long-term outcomes.

CONCLUSION

This paper describes the Paris consensus on the definitions and diagnostic criteria for seronegative CD and chronic NCEs in adults.

Bacterial infection-driven lymphomagenesis

PURPOSE OF REVIEW

The first convincing evidence for a causal relationship between bacterial infection and lymphomagenesis came from the link between gastric lymphoma and chronic Helicobacter pylori gastritis. This review will summarize the current epidemiological, clinical, and biological evidence of a causative role of bacteria in the development of malignant lymphomas, particularly, the extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue type.

RECENT FINDINGS

Other microorganisms have been associated with specific extranodal lymphoma sites with variable and not always definitive, evidence, including Chlamydia psittaci , Borrelia burgdorferi , Campylobacter jejuni and, most recently, Coxiella Burnetii . According to most plausible models, lymphoma growth is a consequence of continuous antigenic stimulation induced by chronic infection. However, some evidence of a direct oncogenic role of H. pylori has been provided, too.

SUMMARY

Lymphomas are not the result of a single cause but multifactorial diseases, influenced by a variety of genetic and environmental elements. Hence, ascertaining the specific contribution of bacterial infections is not always easy. Nevertheless, the eradication of the associated chronic infection may result in sustained lymphoma regression. Moreover, the association between infections and lymphoma may offer opportunities for reducing lymphoma incidence by preventing the predisposing infections or treating them early.

Immunoproliferative Small Intestinal Disease Diagnosed by Double-balloon Endoscopy with Biopsy Sampling

We herein report an 80-year-old man diagnosed with immunoproliferative small intestine disease (IPSID) via small bowel endoscopy with a biopsy. He developed persistent diarrhea and subsequently presented with hypoproteinemia and moderate anemia. Transanal double-balloon endoscopy showed prominent villous edema in the middle and lower ileum, while a histological examination showed high lymphocyte/plasma cell infiltration in the mucosal layer. Furthermore, an immunostaining analysis showed that Cluster of differentiation (CD) 3 and CD20 were partially positive, while CD138 was diffusely positive. Immunoglobulin A positivity was also observed. He was diagnosed with IPSID and received a nutritional agent and minocycline. After three months, the patients' symptoms improved.

Management of Extranodal Marginal Zone Lymphoma: Present and Upcoming Perspectives

Simple Summary

Extranodal marginal zone lymphoma distinguishes itself from other indolent lymphomas due to its unique pathophysiology and natural history. This is reflected in its management, where next to traditional treatment strategies such as observation, radiotherapy or chemotherapy, eradication of the causal agent and even surgery represent important aspects of therapy. This review focuses on the particular aspects of this indolent lymphoma that affect management and summarizes the current evidence and different guidelines.

Abstract

Extranodal marginal zone lymphoma (EMZL) encompasses a subgroup of non-Hodgkin lymphomas that often present with localized involvement and may manifest in a diversity of organs and tissues. EMZL pathogenesis is in some cases linked to chronic inflammation/infection, which may impose additional diagnostic and clinical challenges. The most studied and established connection is the presence of Helicobacter pylori in gastric EMZL. Due to its heterogeneity of presentation and intricate pathological features, treatment can be complex, and staging systems are decisive for the choice of therapy. Nevertheless, there is no consensus regarding the most suitable staging system, and recommendations vary among different countries. As a rule of thumb, in limited stages, a local therapy with surgery or radiation is the preferred option, and it is potentially curative. Of note, eradicating the causal agent may be an important step of treatment, especially in gastric EMZL, in which Helicobacter pylori eradication remains the first-line therapy for the majority of patients. In patients with more advanced stages, watch-and-wait is a valuable option, especially amongst those without clear indications for systemic therapy, and it may be carried on for several years. If watch-and-wait is not an option, systemic therapy may be needed. Even though several agents have been tested as monotherapy or in combination in recent years, there is no consensus regarding the first-line therapy, and decisions can vary depending on individual factors, such as age, clinical performance and stage. This review aims to discuss the several aspects of EMZL, including genetic milieu, pathogenesis and staging systems, that may influence the choice of therapy. In addition, we present a summary of evidence of several systemic therapies, compare different recommendations worldwide and discuss future perspectives and novelties in its therapy.

The Evolution of Our Understanding of Immunoproliferative Small Intestinal Disease (IPSID) over Time

Immunoproliferative small intestinal disease (IPSID) is an uncommon disease with a higher prevalence in the developing world. IPSID diagnosis relies mainly on a tissue biopsy and a high index of suspicion. Treatment options are variable; however, they mainly include anthracycline-based chemotherapy with or without antibiotics in advanced stages. Because of the paucity of IPSID, our perception of the disease remains narrow, and investigating the optimal lines of therapy and prevention without a complete comprehension of the disease is challenging. In our review, we explore the expansion of knowledge about IPSID, which has been developing over the years, to help increase the detection of IPISD cases and further research the most appropriate lines of therapy and prevention.

Imaging of Bowel Lymphoma: A Pictorial Review

Intestinal lymphoma, although rare, is the second most common extra-nodal site of lymphoma, following stomach. It is usually secondary to systemic involvement and is predominantly of non-Hodgkin's subtype. In addition to the risk factors for lymphomas occurring elsewhere, certain risk factors are specific for intestinal lymphoma. These include enteropathies such as celiac disease and inflammatory bowel disease. Imaging is the cornerstone in the management of intestinal lymphoma. Contrast-enhanced computed tomography or positron emission tomography-computed tomography are the preferred modalities for diagnosis, staging, monitoring response to treatment, and for follow-up evaluation. Bowel lymphomas can have various morphological patterns on imaging; however, certain characteristic features, if present, may prove invaluable in its diagnosis. Hence, it is imperative to be acquainted with the myriad of imaging findings in bowel lymphoma and its complications which may not only help in vivo distinction from other commoner bowel lesions but alter the management accordingly.

Mucosa-Associated Lymphoid Tissue (MALT) Lymphoma in the Gastrointestinal Tract in the Modern Era

Extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) typically arises from sites such as the stomach, where there is no organized lymphoid tissue. Close associations between Helicobacter pylori and gastric MALT lymphoma or Campylobacter jejuni and immunoproliferative small intestinal disease (IPSID) have been established. A subset of tumors is associated with chromosomal rearrangement and/or genetic alterations. This disease often presents as localized disease, requiring diverse treatment approaches, from antibiotic therapy to radiotherapy and immunochemotherapy. Eradication therapy for H. pylori effectively cures gastric MALT lymphoma in most patients. However, treatment strategies for H. pylori-negative gastric MALT lymphoma are still challenging. In addition, the effectiveness of antibiotic therapy has been controversial in intestinal MALT lymphoma, except for IPSID. Endoscopic treatment has been noted to usually achieve complete remission in endoscopically resectable colorectal MALT lymphoma with localized disease. MALT lymphoma has been excluded from post-transplant lymphoproliferative disorders with the exception of Epstein–Barr virus (EBV)-positive marginal zone lymphoma (MZL). We also describe the expanding spectrum of EBV-negative MZL and a close association of the disease with the gastrointestinal tract.

Ileal mucosa-associated lymphoid tissue lymphoma diagnosed after emergency surgery: A case report and literature review

Introduction and importance

Extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue, also called MALT lymphoma, is one of the entities of marginal zone lymphomas. These lymphomas are originated from indolent B-cell lymphomas and involve many organs such as the gastrointestinal tract, salivary gland, skin, lung, thyroid or breast. Ileal MALT lymphoma is relatively rare and clinical symptoms are usually atypical.

Case presentation

We report a case of a 99-year-old man who admitted to the emergency department with increasing and colicky periumbilical pain, vomiting and constipation. Non-contrast-enhanced computed tomography suggested small bowel obstruction due to phytobezoar. Intraoperatively, surgeon discovered the tumor at the site of phytobezoar. Histologically, there was a diffuse infiltration comprised of small to medium sized lymphocytes with monocytoid features. Immunohistochemical result confirmed CD20 positive B-lymphocytes and the Ki-67 proliferation index was 10%. Ileal mucosa-associated lymphoid tissue lymphoma was diagnosed based on histological findings and immunohistochemistry.

Discussion

MALToma of the gastrointestinal tract is related to chronic antigenic, inflammatory bowel disease and malabsorption syndromes. However, the etiology of ileal MALToma is unclear. Moreover, symptom of ileal MALToma is really not typical and overleaped in the context of small intestinal obstruction. It should be differentiated small intestinal MALToma from immunoproliferative small intestinal disease and an alpha heavy chain disease.

Conclusion

Ileal MALT lymphoma remains little known in many previous studies. It is really difficult to preoperatively diagnose. The combination of clinical presentation, postoperative histology and immunohistochemistry contribute to diagnosis and carry out appropriate management.

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Ileal MALT lymphoma is relatively rare compared to others gastrointestinal MALT lymphomas and symptoms are usually atypical.

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A 99-year-old man was hospitalized with the symptoms of bowel obstruction.

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Emergency surgery, postoperative histology and immunohistochemistry confirmed ileal MALT lymphoma.

Primary Intestinal Lymphoma: Clinicopathological Characteristics of 55 Patients

Introduction

Gastrointestinal (GI) tract is the most common site of extranodal lymphoma accounting for 30–40% of the cases. In Western countries, stomach is the most common site of GI lymphoma, whereas in the Middle East and Mediterranean countries, small intestine is commonly involved. Studies about primary intestinal lymphoma (PIL) are heterogeneous in anatomical distribution, presentation, and histological subtypes. The present study was aimed at studying the anatomical distribution, histological subtypes, and clinical characteristics at tertiary care centers.

Materials and methods

The present study was retrospective, conducted between 2006 and 2020. Patient's data were collected from institutional medical records. PIL was diagnosed by Lewin's criteria. After histological diagnosis, PIL was classified as per the World Health Organization (WHO) criteria and staging was done according to the Ann Arbor classification as modified by Musshoff.

Results

A total of 941 lymphoma cases were diagnosed during the study period between 2006 and 2020 consisting of 238 Hodgkin's lymphoma and 703 non-Hodgkin's lymphoma (NHL) cases. PIL constituted 5.8% of all lymphoma cases (55 out of 941) and 50.9% (55 of 108) of all primary GI lymphoma. Median age at diagnosis was 44 years and comprised predominantly males (85.45%). Diffuse large B-cell lymphoma (DLBCL) and mucosa-associated lymphoid tissue (MALT) lymphoma were the most common histological subtype (78%) seen. Two patients with primary Hodgkin's lymphoma involving the intestine were seen. T-cell lymphoma was seen in three (5.4%) patients. Ileocecal region was the most common site involved (27%). The common presenting complaints were intestinal obstruction (40%) requiring surgical resection and abdominal pain (32%). Majority of the patients presented in the early stages (I and II).

Conclusion

Our study demonstrates the pattern of distribution and various histological subtypes of PIL including the rare variants like primary intestinal Hodgkin's lymphoma. Relatively more number of patients presented with intestinal obstruction requiring surgery in comparison with other studies.

How to cite this article

Malipatel R, Patil M, Rout P, et al. Primary Intestinal Lymphoma: Clinicopathological Characteristics of 55 Patients. Euroasian J Hepato-Gastroenterol 2021;11(2):71–75.

Gastrointestinal lymphoproliferative lesions: a practical diagnostic approach

The gastrointestinal tract (GI) is the primary site of lymphoproliferative lesions, spanning from reactive lymphoid hyperplasia to overt lymphoma. The diagnosis of these diseases is challenging and an integrated approach based on clinical, morphological, immunohistochemical and molecular data is needed. To reach to confident conclusions, a stepwise approach is highly recommended. Histological evaluation should first assess the benign versus neoplastic nature of a given lymphoid infiltrate. Morphological and phenotypic analyses should then be applied to get to a definite diagnosis.

This review addresses the key histological features and diagnostic workup of the most common GI non-Hodgkin lymphomas (NHLs). Differential diagnoses and possible pitfalls are discussed by considering distinct groups of lesions (i.e. small to medium B-cell NHLs; medium to large B-cell NHLs; T-cell NHLs; and mimickers of Hodgkin lymphoma). The key clinical and epidemiological features of each entity are also described.

Microbiota and cancer: current understanding and mechanistic implications

During last few decades, role of microbiota and its importance in several diseases has been a hot topic for research. The microbiota is considered as an accessory organ for maintaining normal physiology of an individual. These microbiota organisms which normally colonize several epithelial surfaces are known to secrete several small molecules leading to local and systemic effects on normal biological processes. The role of microbiota is also established in carcinogenesis as per several recent findings. The effects of microbiota on cancer is not only limited to their contribution in oncogenesis, but the overall susceptibility for oncogenesis and its subsequent progression, development of coinfections, and response to anticancer therapy is also found to be affected by microbiota. The information about microbiota and subsequent contributions of microbes in anticancer response motivated researchers in development of microbes-based anticancer therapeutics. We provided current status of microbiota contribution in oncogenesis with special reference to their mechanistic implications in different aspects of oncogenesis. In addition, the mechanistic implications of bacteria in anticancer therapy are also discussed. We conclude that several mechanisms of microbiota-mediated regulation of oncogenesis is known, but approaches must be focused on understanding contribution of microbiota as a community rather than single organisms-mediated effects.

Treating chronic diarrhea: A systematic review on Immunoproliferative Small Intestinal Disease (IPSID)

Immunoproliferative Small Intestinal Disease (IPSID) is a disease characterized by extra-nodal marginal zone B-cell lymphoma with villous atrophy in the small intestine, causing chronic intermittent non-bloody diarrhea. Although originally associated with the Mediterranean region, this disease is present in many countries worldwide and may have been underreported due to its complicated diagnosis and scarce scientific literature, especially in regards to treatment. This study aims to review IPSID clinical features, therapeutic options, and treatment outcomes to help physicians identify and treat IPSID. Using PRISMA guidelines, a systematic review of articles was conducted on PubMed database with search terms including IPSID, therapy, treatment, and outcomes. Inclusion and exclusion criteria were used to select 33 English language articles published from the year 2000–2020 that included relevant clinical information about IPSID treatment. Data were extracted independently by at least two authors to reduce the introduction of potential bias. There were 22 case reports, 7 reviews, 1 research article, 1 prospective study, 1 letter to the editor and 1 memoriam in which 76 patients were identified. Epidemiological analysis showed a mean patient age of 32 years old, 2.4:1 mal to female ratio and heterogeneous ethnicities, with 16 Europeans (43.2%) and 12 Asians (32.4%). Chief symptoms included chronic diarrhea (53/76, 69.7%), weight loss (49/76, 64.4%), malabsorption (38/76, 50%), abdominal pain (32/76, 42.1%), and finger clubbing (24/76, 31.6%). Patients stratified into the early disease stage (Galian A) were treated with tetracycline antibiotics, corticosteroids, and non-pharmacological supplements with mostly with complete or partial remission. Late stages (Galian B or C), were treated mostly with anthracycline-based chemotherapy, and occasionally surgery, radiotherapy, or rituximab. This work offers a targeted approach to diagnosing and treating IPSID to aid physicians and serve as a treatment guideline recommendation for future public policies and clinical studies.

Bacterial Infection and Non-Hodgkin B-Cell Lymphoma: Interactions between Pathogen, Host and the Tumor Environment

Non-Hodgkin B-cell lymphomas (NHL) are a heterogeneous group of lymphoid neoplasms with complex etiopathology, rich symptomatology, and a variety of clinical courses, therefore requiring different therapeutic approaches. The hypothesis that an infectious agent may initiate chronic inflammation and facilitate B lymphocyte transformation and lymphogenesis has been raised in recent years. Viruses, like EBV, HTLV-1, HIV, HCV and parasites, like Plasmodium falciparum, have been linked to the development of lymphomas. The association of chronic Helicobacter pylori (H. pylori) infection with mucosa-associated lymphoid tissue (MALT) lymphoma, Borrelia burgdorferi with cutaneous MALT lymphoma and Chlamydophila psittaci with ocular adnexal MALT lymphoma is well documented. Recent studies have indicated that other infectious agents may also be relevant in B-cell lymphogenesis such as Coxiella burnettii, Campylobacter jejuni, Achromobacter xylosoxidans, and Escherichia coli. The aim of the present review is to provide a summary of the current literature on infectious bacterial agents associated with B-cell NHL and to discuss its role in lymphogenesis, taking into account the interaction between infectious agents, host factors, and the tumor environment.

Recent advances upper gastrointestinal lymphomas: molecular updates and diagnostic implications

Approximately one-third of extranodal non-Hodgkin lymphomas involve the gastrointestinal (GI) tract, with the vast majority being diagnosed in the stomach, duodenum, or proximal small intestine. A few entities, especially diffuse large B-cell lymphoma and extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue, represent the majority of cases. In addition, there are diseases specific to or characteristic of the GI tract, and any type of systemic lymphoma can present in or disseminate to these organs. The recent advances in the genetic and molecular characterisation of lymphoid neoplasms have translated into notable changes in the classification of primary GI T-cell neoplasms and the recommended diagnostic approach to aggressive B-cell tumours. In many instances, diagnoses rely on morphology and immunophenotype, but there is an increasing need to incorporate molecular genetic markers. Moreover, it is also important to take into consideration the endoscopic and clinical presentations. This review gives an update on the most recent developments in the pathology and molecular pathology of upper GI lymphoproliferative diseases.

Hematologic malignancies of the gastrointestinal luminal tract

Hematologic malignancies include several lymphoproliferative and myeloproliferative disorders, many of which are frequently encountered in current health care settings. These malignancies frequently affect the gastrointestinal (GI) tract, either by secondary extranodal or extramedullary extension to the GI tract, or as a primary process arising in the GI tract. In fact, the GI tract may represent the most common extranodal site of involvement in many of them, such as lymphoma. Furthermore, in the current era of improved cancer treatment and advanced transplant procedures with increased survival, it has been quite common to encounter GI involvement by these malignancies through the disease course. Post-transplant lymphoproliferative disorder following kidney transplantation, for example, very commonly involves the GI tract. Other conditions that can involve the GI tract include multiple myeloma, plasmacytoma, myeloid sarcoma, mastocytosis, and Castleman disease. Imaging diagnosis of these malignancies can be challenging, since they are much less common than primary GI cancers and both share many common imaging features as well. However, certain imaging features, particularly in combination with a matching clinical scenario, play a pivotal role in diagnosing these conditions and directing further evaluation. In this article, we review common and rare hematologic malignancies of the GI tract and discuss their pathophysiologic, clinical, and imaging features.

Marginal zone B-cell lymphoma: lessons from Western and Eastern diagnostic approaches

Marginal zone B-cell lymphomas (MZLs) are a group of clinically indolent B-cell lymphomas postulated to derive from memory B lymphocytes in the 'marginal zone' of secondary lymphoid tissue. Today, MZL is recognised as a nosological umbrella term encompassing distinct entities with some shared phenotypic and genotypic features, including extranodal marginal zone B-cell lymphoma (EMZL) or mucosa-associated lymphoid tissue (MALT) lymphoma, splenic MZL, and nodal MZL, accounting for approximately 70%, 20%, and 10% of MZLs, respectively. These lymphomas share some phenotypic and genotypic features and have some variants and related provisional diseases, but are different in regards to their clinical and molecular characteristics. In addition, they are frequently associated with chronic antigenic stimulation represented either by infectious agents, particularly bacteria and viruses, or autoimmune diseases as exemplified by Sjögren syndrome, Hashimoto thyroiditis, and newly recognised IgG4-related disease. Furthermore, several chromosomal translocations have been identified in EMZL. In this review, we will focus on the updated histopathological criteria and the main problems with differential diagnoses in order to aid the diagnostic approach in our routine practice.

Colorectal Lymphoma: A Contemporary Case Series

BACKGROUND

Colon and rectal lymphomas are rare and can occur in the context of posttransplant lymphoproliferative disorder. Evidence-based management guidelines are lacking.

OBJECTIVE

The purpose of this study was to characterize the presentation, diagnosis, and management of colorectal lymphoma and to identify differences within the transplant population.

DESIGN

This was a retrospective review of patients evaluated for colorectal lymphoma between 2000 and 2017. Patients were identified through clinical note queries.

SETTINGS

Four hospitals within a single health system were included.

PATIENTS

Fifty-two patients (64% men; mean age = 64 y; range, 26-91 y) were identified. No patient had <3 months of follow-up. Eight patients (15%) had posttransplant lymphoproliferative disorder.

MAIN OUTCOME MEASURES

Overall survival, recurrence, and complications in treatment pathway were measured.

RESULTS

Most common presentations were rectal bleeding (27%), abdominal pain (23%), and diarrhea (23%). The most common location was the cecum (62%). Most frequent histologies were diffuse large B-cell lymphoma (48%) and mantle cell lymphoma (25%). Posttransplant lymphoproliferative disorder occurred in the cecum (n = 4) and rectum (n = 4). Twenty patients (38%) were managed with chemotherapy; 25 patients (48%) underwent primary resection. Mass lesions had a higher risk of urgent surgical resection (35% vs 8%; p = 0.017). Three patients (15%) treated with chemotherapy presented with perforation requiring emergency surgery. Overall survival was 77 months (range, 25-180 mo). Patients with cecal involvement had longer overall survival (96 vs 26 mo; p = 0.038); immunosuppressed patients had shorter survival (16 vs 96 mo; p = 0.006). Survival in patients treated with surgical management versus chemotherapy was similar (67 vs 105 mo; p = 0.62).

LIMITATIONS

This was a retrospective chart review, with data limited by the contents of the medical chart. This was a small sample size.

CONCLUSIONS

Colorectal lymphoma is rare, with variable treatment approaches. Patients with noncecal involvement and chronic immunosuppression had worse overall survival. Patients with mass lesions, particularly cecal masses, are at higher risk to require urgent intervention, and primary resection should be considered. See Video Abstract at http://links.lww.com/DCR/A929.

Overview in the clinical management of patients with seronegative villous atrophy

Differential diagnosis and management of enteropathies found in the context of seronegative villous atrophy (VA) are still a clinical challenge. Although seronegative coeliac disease may be the most frequent cause of serology-negative VA, other conditions must be taken into account in the differential diagnosis of seronegative VA. The rarity of these enteropathies with frequent overlapping of histological features may result in misclassification of such patients as affected by a seronegative or a refractory form of coeliac disease with consequent inappropriate treatments and long-term morbidity. The aim of this review is to summarize the current knowledge and to provide an evidence base and practical algorithmic approach for the investigation and management of seronegative VA.

Recent advances in understanding the biology of marginal zone lymphoma

There are three different marginal zone lymphomas (MZLs): the extranodal MZL of mucosa-associated lymphoid tissue (MALT) type (MALT lymphoma), the splenic MZL, and the nodal MZL. The three MZLs share common lesions and deregulated pathways but also present specific alterations that can be used for their differential diagnosis. Although trisomies of chromosomes 3 and 18, deletions at 6q23, deregulation of nuclear factor kappa B, and chromatin remodeling genes are frequent events in all of them, the three MZLs differ in the presence of recurrent translocations, mutations affecting the NOTCH pathway, and the transcription factor Kruppel like factor 2 ( KLF2) or the receptor-type protein tyrosine phosphatase delta ( PTPRD). Since a better understanding of the molecular events underlying each subtype may have practical relevance, this review summarizes the most recent and main advances in our understanding of the genetics and biology of MZLs.

Heavy Chain Disease of the Small Bowel

PURPOSE OF REVIEW

The purpose of this review is to discuss current knowledge and recent findings regarding pathogenesis, outcome, and treatment for heavy chain disease (HCD) involving the small bowel, focusing on alpha HCD or immunoproliferative small intestinal disease (IPSID), the HCD subtype typically affecting the small bowel.

RECENT FINDINGS

A link between Campylobacter jejuni infection and IPSID has been established, but there is controversy as to the role played by this organism in disease pathogenesis. While cytogenetic abnormalities involving various immunoglobulin loci and PAX5 have been reported, these have been described in rare, single cases, limiting their ability to shed further light on disease pathogenesis. IPSID is typically regarded as a pre-lymphomatous condition with eventual progression to frank lymphoma; however, recent reports of longstanding non-progressive cases have expanded its clinical spectrum. IPSID is an uncommon disorder affecting the small intestine. This review focuses on current knowledge and novel insight regarding its pathogenesis, outcome, and treatment, with an emphasis on future directions.

Heavy-Chain Diseases and Myeloma-Associated Fanconi Syndrome: an Update

The heavy chain diseases (HCDs) are rare B-cell malignancies characterized by the production of a monoclonal immunoglobulin heavy chain without an associated light chain. There are three types of HCD, defined by the class of immunoglobulin heavy chain produced: IgA (α-HCD), IgG (γ-HCD), and IgM (μ-HCD). Alpha-HCD is the most common and usually occurs as intestinal malabsorption in a young adult from a country of the Mediterranean area. Gamma- and μ-HCDs are rarer and associated with a B-cell non-Hodgkin lymphoma that produces an abnormal Ig heavy chain. These patients may occasionally be diagnosed with a monoclonal gammopathy of undetermined significance (MGUS). Fanconi syndrome, on the other hand, can be primary (inherited) or secondary (acquired). The only exception to this rule is the idiopathic form. Adult acquired Fanconi syndrome can be a rare complication of a monoclonal gammopathy. At diagnosis, most patients have an MGUS or smoldering multiple myeloma, with renal failure and evidence of osteomalacia. During follow-up, patients can develop an end-stage renal disease. Chemotherapy provides little benefit on renal function.

Overview on the management of non-gastric MALT lymphomas

Extranodal marginal zone B-cell lymphomas (EMZLs) of the mucosa-associated lymphoid tissue (MALT) are indolent lymphomas which can present at any extranodal site. The most frequent localizations (other than stomach) are ocular adnexa, salivary gland, skin, lung and thyroid. Chronic inflammation and antigenic stimulation are a potential risk for the development of MALT lymphomas. While Helicobacter Pylori (HP) is known to be associated with gastric MALT lymphoma and antibiotic therapy is effective in the setting of HP-positive, other microorganisms (such as Chlamydophila Psittaci, Campylobacter Jejiuni, Borrelia Burgdoferi) have been implicated in the pathogenesis of non-gastric MALT lymphomas. However, antibiotic therapy has not been extensively investigated for the non-gastric type, except for ocular adnexal MALT lymphoma, which could benefit from an upfront treatment with doxycycline. Surgery, radiotherapy, Rituximab alone or in combination with chemotherapy and "chemo-free" approaches, including lenalidomide, have shown efficacy in the treatment of non-gastric MALT lymphomas.

Associations of Autoimmunity, Immunodeficiency, Lymphomagenesis, and Gut Microbiota in Mice with Knockins for a Pathogenic Autoantibody

A number of mouse strains transgenic for B-cell receptors specific for nucleic acids or other autoantigens have been generated to understand how autoreactive B cells are regulated in normal and autoimmune mice. Previous studies of nonautoimmune C57BL/6 mice heterozygous for both the IgH and IgL knockins of the polyreactive autoantibody, 564, produced high levels of autoantibodies in a largely Toll-like receptor 7-dependent manner. Herein, we describe studies of mice homozygous for the knockins that also expressed high levels of autoantibodies but, unlike the heterozygotes, exhibited a high incidence of mature B-cell lymphomas and enhanced susceptibility to bacterial infections. Microarray analyses and serological studies suggested that lymphomagenesis might be related to chronic B-cell activation promoted by IL-21. Strikingly, mice treated continuously with antibiotic-supplemented water did not develop lymphomas or abscesses and exhibited less autoimmunity. This mouse model may help us understand the reasons for enhanced susceptibility to lymphoma development exhibited by humans with a variety of autoimmune diseases, such as Sjögren syndrome, systemic lupus erythematosus, and highly active rheumatoid arthritis.

A Bacterial Cause of Cancer: An Historical Essay

This article reviews the history of the discovery of microbes that increase the risk of cancer of some tissues with a special emphasis on the bacterium Helicobacter pylori and the role played by two Australian physicians, neither schooled in research, who had open minds about the shibboleth that mycobacteria (acid-fast organisms) can survive the acid environment of the stomach, but that other pathogenic bacteria cannot. They discovered one of the most important human pathogens, Helicobacter pylori, and showed it capable of inducing severe gastric inflammatory disease. Subsequently, others built on their observations and showed it capable of inducing two gastric neoplasms: carcinoma and lymphoma. The Oncologist 2017;22:542-548.

Mucosa-associated lymphoid tissue (MALT) variant of primary rectal lymphoma: a review of the English literature

PURPOSE

Primary rectal lymphoma (PRL) is the third most common cause of rectal cancer following adenocarcinoma (90-95 %) and carcinoid (5 %). The most common variant of PRL is the mucosa-associated lymphoid tissue (MALT) type. To date, no study has been able to recommend an optimal treatment algorithm for this rare disease. The aim of our study was to review the English literature on primary rectal MALT lymphoma.

METHODS

A review of the English literature was conducted to identify articles describing the MALT variant of PRL.

RESULTS

Fifty-one cases were identified. A complete response was achieved in 12 of 19 cases treated with Helicobacter pylori eradication therapy, 5 of 6 with radiation, 2 of 4 cases with chemotherapy, 2 of 4 with endoscopic resection, 6 of 8 cases with surgical resection, and all 8 with combination therapies. Cases failing initial therapies were responsive to various second-line treatments. Two cases spontaneously regressed with observation alone.

CONCLUSION

Complete regression of primary rectal MALT lymphoma was achieved using various therapeutic strategies, although the numbers of different treatment modalities are too small to draw definitive conclusions.

Chronic diarrhea associated with high serum level of immunoglobulin A and diffuse infiltration of plasma cell in small intestine: A case report

RATIONALE

Chronic diarrhea in adult patients due to various causes is very common in clinic, but patient suffering with mal-absorption due to immunoproliferative small intestinal disease was rarely reported in China.

PATIENT CONCERNS AND DIAGNOSES

A 35-year-old female presented with more than three years history of chronic diarrhea, rickets, high serum value of immunoglobulin A protein, and anemia. Bone marrow aspiration suggested that the patient was in a sideropenic and megalobastic anemia stage. Duodenal and ileac biopsies revealed atrophy and blunting villi. The bowel lamina propria was infiltrated with slightly increased intraepithelial lymphocytes and mainly with diffuse plasma cells. The following enzyme labeling immunohistochemistry results were strongly positive to alpha-heavy-chain. Computed tomography manifested she had diffuse thickening of small intestine wall. At last a diagnosis of immunoproliferative small intestinal disease was made.

INTERVENTIONS AND OUTCOMES

On the first month, the patient was treated with vitamin D supplements, calcium, magnesium, potassium, iron, folic acid, mecobalamin replacements and microflora probiotics. The patient frequency of water diarrhea alleviated slightly, but her weight loss, anxiety neurosis and other disorders were still severe. After taking with prednisone (40 mg per day, and gradually reduced to the lowest dose) for another month, the symptoms was gradually subsided.

LESSONS

The study shows that immunohistochemical staining for alpha-heavy chain proteins should be completed on small intestine biopsy specimens if the patient is suspected a diagnosis of immunoproliferative small intestinal disease.

Clinical aspects and therapy of gastrointestinal MALT lymphoma

Extranodal marginal zone B-cell lymphomas of the mucosa associated lymphoid tissue (MALT) arise from lymphoid populations that are induced by chronic inflammation in extranodal sites. Among the MALT lymphomas, gastrointestinal (GIT) MALT lymphoma is the most frequent compared to non-GIT MALT lymphoma arising from other sites. Gastric MALT lymphoma has been the first to be described with the evidence of an etiopathogenetic link provided by the association between Helicobacter pylori-positive gastritis and gastric MALT lymphoma. Indeed, successful eradication of this micro-organism with antibiotics can be followed by a lymphoma regression in most cases. When there is no association with Helicobacter pylori, there is no clear therapeutic consensus. Both radiotherapy and systemic treatments with chemotherapy and anti-CD20 antibodies are efficacious and thus the experience of individual centers and each patient's preferences in terms of adverse effects are important parameters in the decision process.

Intraepithelial lymphocytes, scores, mimickers and challenges in diagnosing gluten-sensitive enteropathy (celiac disease)

The upper digestive tract is routinely scoped for several causes of malabsorption, and the number of duodenal biopsy specimens has increased notably in the last 10 years. Gluten-sensitive enteropathy (GSE) is an autoimmune disease, which shows an increasing prevalence worldwide and requires a joint clinico-pathological approach. The classical histopathology of GSE with partial or total villous blunting is well recognized, but the classification of GSE is not straightforward. Moreover, several mimickers of GSE with intraepithelial lymphocytosis have been identified in the last 20 years, with drug interactions and medical comorbidities adding to the conundrum. In this review, we report on the normal duodenal mucosa, the clinical presentation and laboratory diagnosis of GSE, the duodenal intraepithelial lymphocytes and immunophenotype of GSE-associated lymphocytes, the GSE mimickers, the differences "across oceans" among guidelines in diagnosing GSE, and the use of a synoptic report for reporting duodenal biopsies in both children and adults in the 21st century.

Identification of Mucosa-Invading and Intravascular Bacteria in Feline Small Intestinal Lymphoma

Persistent bacterial infections of the gastrointestinal mucosa are causally linked to gastric carcinoma and mucosa-associated lymphoid tissue (MALT) lymphoma in people and laboratory animals. We examined the relationship of mucosa-associated bacteria to alimentary lymphoma in cats. Intestinal biopsies from 50 cats with alimentary lymphoma (small cell, n = 33; large cell, n = 17) and 38 controls without lymphoma (normal to minimal change on histopathology, n = 18; lymphocytic-plasmacytic enteritis, n = 20) were evaluated. The number and spatial distribution of bacteria (ie, in luminal cellular debris, villus-associated mucus, adherent to epithelium, mucosal invasion, intravascular, or serosal) were determined by fluorescence in situ hybridization with the eubacterial probe EUB-338. Mucosa-invasive bacteria were more frequently observed in cats with large cell lymphoma (82%, P ≤ .001) than in cats with small cell lymphoma (18%), normal to minimal change on histopathology, and lymphocytic-plasmacytic enteritis (3%). Intravascular bacteria were observed solely in large cell lymphoma (29%), and serosal colonization was more common in cats with large cell lymphoma (57%) than with small cell lymphoma (11%, P ≤ .01), normal to minimal change (8%, P ≤ .01), and lymphocytic-plasmacytic enteritis (6%, P ≤ .001). The high frequency of invasive bacteria within blood vessels and serosa of cats with large cell lymphoma may account for the sepsis-related complications associated with large cell lymphoma and inform clinical management. Further studies are required to determine the role of intramucosal bacteria in the etiopathogenesis of feline alimentary lymphoma.

Recurrence patterns of mucose-associated lymphoid tissue lymphoma after definitive radiation treatment: A single center experience

OBJECTIVES

To evaluate the treatment outcomes in non-gastric and non-nodal mucose-associated lymphoid tissue (MALT) lymphoma patients treated by definitive radiation therapy (RT).

METHODS

A total of 134 patients were analyzed. The RT dose was 30.6 or 36 Gy.

RESULTS

The median follow-up duration for all patients was 51.1 months (range, 3.0-132.4 months). Among the 88 orbital MALT lymphoma patients, 12 had disease recurrence. There were 23 head and neck tumor patients. Two patients experienced relapse, all at out-of-field locations. Gastrointestinal MALT lymphoma was diagnosed in 13 patients, and three showed local (n = 1), distant (n = 1), or local/distant (n = 1) relapse.

CONCLUSION

RT alone is highly effective in achieving local control and long-term survival in localized MALT lymphoma. In orbital MALT, excellent local control is achieved, and relapse is predominantly observed in the contralateral eye. Other head and neck lymphomas are also well controlled.

The spectrum of MALT lymphoma at different sites: biological and therapeutic relevance

Extranodal marginal zone (MZ) B-cell lymphomas of the mucosa-associated lymphoid tissue (MALT) arise from lymphoid populations that are induced by chronic inflammation in extranodal sites. The best evidence of an etiopathogenetic link is provided by the association between Helicobacter pylori–positive gastritis and gastric MALT lymphoma. Indeed, successful eradication of this microorganism with antibiotics can be followed by gastric MALT lymphoma regression in most cases. Other microbial agents have been implicated in the pathogenesis of MZ lymphoma arising at different sites. Apart from gastric MALT lymphoma, antibiotic therapies have been adequately tested only in ocular adnexal MALT lymphomas where upfront doxycycline may be a reasonable and effective initial treatment of patients with Chlamydophila psittaci–positive lymphoma before considering more aggressive strategies. In all other instances, antibiotic treatment of nongastric lymphomas remains investigational. Indeed, there is no clear consensus for the treatment of patients with gastric MALT lymphoma requiring further treatment beyond H pylori eradication or with extensive disease. Both radiotherapy and systemic treatments with chemotherapy and anti-CD20 antibodies are efficacious and thus the experience of individual centers and each patient’s preferences in terms of adverse effects are important parameters in the decision process.

Immunoproliferative Small Intestinal Disease Associated with Overwhelming Polymicrobial Gastrointestinal Infection with Transformation to Diffuse Large B-cell Lymphoma

Immunoproliferative small intestinal disease (IPSID) is an extra-nodal B-cell lymphoma most commonly described in the Mediterranean, Africa, and Asia. It is associated with poverty and poor sanitation, and is rarely encountered in developed countries. A 26-year-old previously healthy, Marshallese male was transferred to our facility with a 6-month history of watery diarrhea, weakness, and cachexia refractory to multiple short courses of oral antibiotics. Stool cultures grew Campylobacter jejuni and Vibrio fluvialis. Endoscopic evaluation showed histologic evidence of Helicobacter pylori gastritis and gross evidence of whipworm infection found in the colon. Mesenteric lymph node biopsy cultures grew Escherichia coli. Histopathology and immunohistochemical stains of the small intestine were consistent with IPSID. He subsequently transformed to diffuse large B-cell lymphoma (DLBCL) with tonsillar involvement despite treatment with rituximab and an extended course of antibiotics. Systemic chemotherapy with six cycles of rituximab, cyclophosphamide, vincristine, doxorubicin, prednisone, and lenalidomide, resulted in remission of his diffuse B cell lymphoma. This case is illustrative of IPSID developing in a previously healthy individual due to overwhelming polymicrobial gastrointestinal infection by C. jejuni and other enteric pathogens with subsequent transformation to an aggressive DLBCL. IPSID should be considered in residents of developing countries presenting with refractory chronic diarrhea, weight loss, and mesenteric lymphadenopathy.

From the radiologic pathology archives: gastrointestinal lymphoma: radiologic and pathologic findings

Gastrointestinal (GI) lymphoma encompasses a heterogeneous group of neoplasms that have a common lymphoid origin but variable pathologic and imaging features. Extranodal marginal zone B-cell lymphoma (ENMZL) and diffuse large B-cell lymphoma (DLBCL) are the most common. ENMZL usually occurs in the stomach, where it is associated with chronic infection by Helicobacter pylori, and is typically a superficial spreading lesion that causes mucosal nodularity or ulceration and mild wall thickening. DLBCL may arise de novo or from transformation of ENMZL or other low-grade lymphomas. This form of lymphoma produces extensive wall thickening or a bulky mass, but obstruction is uncommon. Mantle cell lymphoma is the classic cause of lymphomatous polyposis, but multiple polyps or nodules can also be seen with ENMZL and follicular lymphoma. Burkitt lymphoma is usually characterized by an ileocecal mass or wall thickening in the terminal ileum in young children, often in the setting of widespread disease. Primary GI Hodgkin lymphoma, which is rare, may be manifested by a variety of findings, though stenosis is more common than with non-Hodgkin lymphoma. Enteropathy-associated T-cell lymphoma is frequently associated with celiac disease and is characterized by wall thickening, ulceration, and even perforation of the jejunum. Accurate radiologic diagnosis of GI lymphoma requires a multifactorial approach based on the clinical findings, site of involvement, imaging findings, and associated complications.

Recent advances in intestinal lymphomas

A large variety of lymphoma types may develop as primary intestinal neoplasms in the small intestines or, less often, in the colorectum. Among these are a few entities such as enteropathy-associated T-cell lymphoma or immunoproliferative small intestinal disease that, essentially, do not arise elsewhere than in the gastrointestinal tract. In most instances the primary intestinal lymphomas belong to entities that also occur in lymph nodes or other mucosal sites, and may show some peculiar features. In the case of follicular lymphoma, important differences exist between the classical nodal cases and the intestinal cases, considered as a variant of the disease. It is likely that the local intestinal mucosal microenvironment is a determinant in influencing the pathobiological features of the disease. In this review we will present an update on the clinical, pathological and molecular features of the lymphoid neoplasms that most commonly involve the intestines, incorporating recent developments with respect to their pathobiology and classification. We will emphasize and discuss the major differential diagnostic problems encountered in practice, including the benign reactive or atypical lymphoid hyperplasias, indolent lymphoproliferative disorders of T or natural killer (NK) cells, and Epstein-Barr virus (EBV)-related lymphoproliferations.

Ileal mucosa-associated lymphoid tissue lymphoma presenting with small bowel obstruction: a case report

Extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT Lymphoma) of the gastrointestinal tract commonly involves the stomach in the setting of concurrent Helicobacter pylori (H. pylori) infection. Primary ileal MALT lymphoma is rare, and has not been associated with a specific infectious disease. We report a case of a 58-year-old man who presented to the emergency department with constipation and abdominal distension, and signs of an obstructing mass on computed tomography scan. A small bowel resection was performed which revealed an 8 cm saccular dilatation with thickened bowel wall and subjacent thickened tan-yellow tissue extending into the mesentery. Histologically, there was a diffuse lymphoid infiltrate consisting of small atypical cells with monocytoid features. These cells were CD20-positive B-lymphocytes that co-expressed BCL-2 and were negative for CD5, CD10, CD43, and cyclin D1 on immunohistochemical studies. Kappa-restricted plasma cells were also identified by in situ hybridization. The overall proliferation index was low with Ki-67 immunoreactivity in approximately 10 % of cells. No areas suspicious for large cell or high grade transformation were identified. The pathologic findings were diagnostic of an extranodal marginal zone lymphoma involving the ileum, with early involvement of mesenteric lymph nodes. Small hypermetabolic right mesenteric and bilateral hilar lymph nodes were identified by imaging. The bone marrow biopsy showed no evidence of involvement by lymphoma. The patient was clinically considered advanced stage and opted for therapy with rituximab infusions. After six months of therapy, follow-up radiologic studies demonstrated significant decrease in size of the mesenteric lymph nodes.

Emerging role of infectious etiologies in the pathogenesis of marginal zone B-cell lymphomas

Extranodal marginal zone B-cell lymphomas of the mucosa-associated lymphoid tissue (MALT) arise from lymphoid populations that are induced by chronic inflammation in extranodal sites. The most frequently affected organ is the stomach, where MALT lymphoma is incontrovertibly associated with a chronic gastritis induced by a microbial pathogen, Helicobacter pylori. Gastric MALT lymphoma therefore represents a paradigm for evaluating inflammation-associated lymphomagenesis, which may lead to a deeper understanding of a possible etiologic association between other microorganisms and nongastric marginal zone lymphomas. Besides infectious etiology, chronic inflammation caused by autoimmune diseases, such as Sjögren syndrome or Hashimoto thyroiditis, can also carry a significant risk factor for the development of marginal zone lymphoma. In addition to the continuous antigenic drive, additional oncogenic events play a relevant role in lymphoma growth and progression to the point at which the lymphoproliferative process may eventually become independent of antigenic stimulation. Recent studies on MALT lymphomas have in fact demonstrated genetic alterations affecting the NF-κB) pathway, a major signaling pathway involved in many cancers. This review aims to present marginal zone lymphoma as an example of the close pathogenetic link between chronic inflammation and tumor development, with particular attention to the role of infectious agents and the integration of these observations into everyday clinical practice. See all articles in this CCR Focus section, "Paradigm Shifts in Lymphoma."

An integrative view of microbiome-host interactions in inflammatory bowel diseases

The intestinal microbiota, which is composed of bacteria, viruses, and micro-eukaryotes, acts as an accessory organ system with distinct functions along the intestinal tract that are critical for health. This review focuses on how the microbiota drives intestinal disease through alterations in microbial community architecture, disruption of the mucosal barrier, modulation of innate and adaptive immunity, and dysfunction of the enteric nervous system. Inflammatory bowel disease is used as a model system to understand these microbial-driven pathologies, but the knowledge gained in this space is extended to less-well-studied intestinal diseases that may also have an important microbial component, including environmental enteropathy and chronic colitis-associated colorectal cancer.