Prevalence of microsatellite instable and Epstein-Barr Virus-driven gastroesophageal cancer in a large Belgian cohort.

Introduction: Patients with gastroesophageal adenocarcinoma (GEC) with microsatellite instability-high (MSI-H) or Epstein Barr Virus positivity (EBV+) might be good candidates for immunotherapy. Incidences of about 10% have been reported for both features, but are dependent on geographical region and disease stage. Aim: The aim is to study the prevalence of MSI-H and EBV+ in a Belgian single center cohort of patients with GEC. Methods: We retrospectively assessed the files of all patients with a newly diagnosed GEC between August, 1st 2018 and February, 29th 2020 at the University Hospitals Leuven, Belgium. Microsatellite instability (MSI) status was determined using immunohistochemistry (IHC) and polymerase chain reaction (PCR). EBV+ was assessed using in situ hybridization (ISH). A case report is provided to illustrate the importance of testing for MSI in GEC. Results: 247 gastroesophageal adenocarcinomas were included in this analysis. 62 (56% stage IV) of those were tested for EBV, but only 1 turned out to be EBV positive (1.6%). 116 patients (44.0% stage IV) were tested for MSI, of which 11 were MSI-H (9.5%). Half of the MSI-H tumors identified were at the gastroesophageal junction (GEJ). A patient with MSI-H metastatic GEC obtained a complete response with nivolumab, which persisted after discontinuation of treatment. Conclusion: While we confirm that about 10% of GECs are MSI-H, the incidence of EBV+ in our cohort (1.6%) is clearly lower than expected. Given the important prognostic and predictive implications, every gastroesophageal cancer should be tested for MSI.

Disseminated histoplasmosis in a kidney liver transplant patient from a non-endemic area: A diagnostic challenge.

Disseminated histoplasmosis is a rare opportunistic infection in non-endemic areas, where the disease is often diagnosed late. The spectrum of clinical manifestations is broad and life-threatening complications occur. We present a detailed case of a kidney liver transplant patient with disseminated histoplasmosis in a non-endemic area. Our case highlights the wide range of pathogens to consider in the immunocompromised patient, the delayed diagnosis of Histoplasmosis Capsulatum in non-endemic areas and the possibility of severe gastrointestinal disease. We also briefly review diagnostic tests and treatment options.

Appendiceal cancer : a review of the literature.

Primary appendiceal cancer is rare and most commonly found incidentally on a surgical specimen after appendectomy for acute appendicitis. This small organ gives rise to different subtypes which are histological and biological distinct. Historically the classification of these tumors has been confusing because of the different nomenclature that is used. This review has broadly classified them into four subgroups: colonic-type adenocarcinoma, mucinous neoplasm, goblet cell carcinoma and neuroendocrine neoplasm. Signet ring cells is not considered as a distinct subgroup but as a histologic feature that can be present in colonic-type adenocarcinoma and mucinous neoplasms. As staging and management of appendiceal tumors depend on these subtypes, an adequate classification of them is important. This review aimed to give an overview of the epidemiology, grading and staging, management and prognosis of these neoplasms. Despite its rarety, specific staging systems and treatment guidelines exist for some subtypes. For other subtypes staging systems and management is extrapolised from colorectal cancer because of the lack of randomised, prospective trials.

Guidelines for an optimal management of a malignant colorectal polyp. What is essential in a pathology report ?

Colorectal cancer (CRC) has become the most common malignancy in our country. Routine screening colonoscopy is on the rise. With the recent advances in endoscopic treatment, many T1 colorectal carcinomas are now found and their percentage amenable to endoscopic resection has increased. Endoscopists and pathologists dealing with the steadily increasing number of excised colorectal polyps have to collaborate closely to optimize patient care. Therapeutic management of patients after endoscopic resection is based on precise histological criteria that determine the risk of metastasis and the need for complementary surgery. This paper summarizes the procedures for the macroscopic management of endoscopic excisions and presents the identified risk factors which should be included in a standardized pathology report.

Loss of protein phosphatase 2A regulatory subunit B56δ promotes spontaneous tumorigenesis in vivo.

Protein Phosphatase 2A (PP2A) enzymes counteract diverse kinase-driven oncogenic pathways and their function is frequently impaired in cancer. PP2A inhibition is indispensable for full transformation of human cells, but whether loss of PP2A is sufficient for tumorigenesis in vivo has remained elusive. Here, we describe spontaneous tumor development in knockout mice for Ppp2r5d, encoding the PP2A regulatory B56δ subunit. Several primary tumors were observed, most commonly, hematologic malignancies and hepatocellular carcinomas (HCCs). Targeted immunoblot and immunohistochemistry analysis of the HCCs revealed heterogeneous activation of diverse oncogenic pathways known to be suppressed by PP2A-B56. RNA sequencing analysis unveiled, however, a common role for oncogenic c-Myc activation in the HCCs, independently underscored by c-Myc Ser62 hyperphosphorylation. Upstream of c-Myc, GSK-3ß Ser9 hyperphosphorylation occurred both in the HCCs and non-cancerous B56δ-null livers. Thus, uncontrolled c-Myc activity due to B56δ-driven GSK-3ß inactivation is the likely tumor predisposing factor. Our data provide the first compelling mouse genetics evidence sustaining the tumor suppressive activity of a single PP2A holoenzyme, constituting the final missing incentive for full clinical development of PP2A as cancer biomarker and therapy target.

Prognostic value of the circumferential resection margin and its definitions in esophageal cancer patients after neoadjuvant chemoradiotherapy.

The accepted importance of a positive circumferential resection margin (CRM) (defined as R1 in the TNM classification) is based on histopathology of the resection specimen obtained after primary surgery in esophageal cancer patients. The aim of this study is to look for the prognostic value of CRM after neoadjuvant chemoradiotherapy and to compare the clinical significance of a histologically CRM < 1 mm from the cut margin (Royal College of Pathologists definition of R1) to a positive cut margin (College of American Pathologists definition of R1) and to ≥1 mm margin (R0) resections in patients with ypT3-esophageal tumors after neoadjuvant chemoradiotherapy. Between 2000 and 2014, 458 patients who received esophagectomy after neoadjuvant chemoradiation therapy were selected. Overall (OS) and disease-free survival (DFS) were calculated by means of Kaplan-Meier curves and compared by Cox regression analysis. There were 163 (35.9%) patients who had a ypT3 tumor; in 118 (72.4%) resection was complete (R0). In 37 (22.7%) patients a CRM < 1 mm was found and 8 (4.9%) had a circumferential R1-resection. CRM involvement was inversely correlated with tumor regression grading, lymph node capsular involvement, and number of positive lymph nodes. On univariate analysis, no statistically significant difference was found between R0-resection and CRM < 1 mm (P = 0.103) for OS, but DFS showed a significant difference (P = 0.025). Circumferential R1-resections showed a significant difference compared to R0-resections for OS and DFS (both P = 0.002). In multivariate analysis, extracapsular lymph node involvement and circumferential R1-resection were withheld as independent prognosticators for OS, whereas extracapsular lymph node involvement, absence of regression on the primary tumor and circumferential R1-resection were withheld for DFS. After correcting for different variables in the multivariate model, CRM < 1 mm showed no statistical difference compared to R0-resections neither for OS nor for DFS. After neoadjuvant chemoradiotherapy, CRM is correlated with biological behavior of the tumor and with therapy response. Furthermore it is an independent prognosticator for OS and DFS. However CRM < 1 mm itself is no independent prognosticator for OS nor DFS survival in multivariable analysis. These results suggest that the definition of R1-resection should be limited to true invasion of the section plane.

Oesophageal biopsies are insufficient to predict final histology after endoscopic resection in early Barrett's neoplasia.

BACKGROUND: Endoscopic resection (ER) with or without ablation is the first choice treatment for early Barrett's neoplasia. Adequate staging is important to assure a good oncological outcome. OBJECTIVE: The purpose of this study was to investigate the diagnostic accuracy of pre-operative biopsies in patients who undergo ER for high-grade dysplasia (HGD) or early adenocarcinoma (EAC) in Barrett's oesophagus (BE) and the cardia. METHODS: Between November 2005-May 2012, 142 ERs performed in 137 patients were obtained. Worst pre-ER and ER histology were compared. Upgrading/downgrading was defined as any more/less severe histological grading on the ER specimen. RESULTS: The accuracy of pre-ER biopsies in predicting final histology was 61%. ER changed the pre-treatment diagnosis in 55 of the 142 procedures (39%) with downgrading in 23 cases (16%) and upgrading from HGD to T1a or T1b in 32 cases (23%). In the majority of upgraded cases, a visible lesion according to the Paris classification could be detected (26/32, 81%). CONCLUSION: The diagnostic accuracy of oesophageal biopsies alone in predicting final pathology in Barrett's dysplasia is only 61%. The majority of upgraded lesions are detectable. When ablative therapy is considered in HGD Barrett's dysplasia a meticulous inspection for and removal of all small visible lesions is mandatory.

Neoadjuvant chemoradiation treatment followed by surgery for esophageal cancer: there is much more than the mandard tumor regression score.

OBJECTIVE: Tumor regression grading (TRG) systems categorize residual tumor volume on the primary tumor after neoadjuvant treatment. Aim was to evaluate the impact of Mandard TRG, residual tumor depth (ypT) and residual lymph node status (ypN) and extent (ELNI) i.e. intracapsular versus extracapsular involvement on overall (OS) and disease-free survival (DFS) in esophageal carcinoma. METHODS: Between 2005 and 2014, 344 patients receiving R0-esophagectomy after neoadjuvant chemoradiation therapy (nCRT) were selected. Mandard TRG, ypTN and ELNI were prospectively recorded. RESULTS: Mandard TRG1 was found in 110 (32%); TRG2 in 120 (35%); TRG3 in 53 (15%); TRG4 in 54 (16%) and TRG5 in 7 (2%) patients. Both OS and DFS showed no significant difference between TRG1 and 2 (p = 0.059 and 0.105, respectively). Therefore, TRG1/2 was classified together as 'major response', TRG3/4 as 'minor response' and TRG5 as 'no response'. Multivariate analysis showed two independent prognosticators for OS (tumor regression response (TRR) and number of positive lymph nodes) and three independent prognosticators for DFS (TRR, ypT and ELNI). CONCLUSION: After nCRT followed by surgery for esophageal carcinoma, number of residual positive lymph nodes as well as TRR are prognosticators for OS. Minor TRR, ypT and extracapsular lymph node invasion are prognosticators for recurrence.

Microsatellite instable vs stable colon carcinomas: analysis of tumour heterogeneity, inflammation and angiogenesis.

BACKGROUND: Microsatellite instability (MSI) accounts for 15% of all colorectal tumours. Several specific clinicopathologicals (e.g., preference for the proximal colon over the distal colon, improved prognosis and altered response to chemotherapeutics) are described for this subset of tumours. This study aimed to analyse morphological, inflammatory and angiogenic features of MSI vs microsatellite stable (MSS) tumours. METHODS: Twenty-seven MSS and 29 MSI, TNM stage matched, colorectal tumours were selected from the archive of the Department of Pathology, UZ Leuven. Morphology was analysed on haematoxylin-eosin sections. Immunohistochemistry for CD3, CD4, CD8, CD20 and CD68 was used to map tumour infiltration in both a digital and traditional microscope-based manner for all distinct morphological components of the tumour. CD31 immunostains were performed to assess angiogenesis. RESULTS: Morphological tumour heterogeneity was a marked feature of MSI tumours, occurring in 53% of the cases as compared with 11% of the MSS tumours (P<0.001). Digital immune quantification showed an increased number of tumour-infiltrating cytotoxic T-lymphocytes (CD8+) in MSI compared with MSS tumours for both the tumour (P=0.02) and peritumoural area (P=0.03). Traditional microscope-based quantification confirmed these results (P<0.001 for both) and, in addition, revealed large numbers of CD68+ macrophages in the peritumoural area of MSI cancers (P=0.001). Moreover, traditional microscope-based analysis was able to distinguish between lymphocytes directly infiltrating the tumoural glands (intra-epithelial) and those infiltrating only the neoplastic stroma around the glands (intratumoural). Quantification showed high numbers of intra-epithelial CD3+, CD4+, CD8+, CD20+ and CD68+ cells in MSI compared with MSS cancers (P<0.001, P=0.01, P<0.001, P<0.001 and P=0.006, respectively). Higher microvessel density (MVD) was observed in MSI tumours compared with their MSS counterpart. CONCLUSIONS: Mixed morphology, reflecting tumour heterogeneity, is an important feature of MSI tumours and may have both diagnostic and therapeutic impact. The inflammatory reaction also presented with significant differences in MSI vs MSS colorectal tumours. MSI cancers showed mainly infiltration by cytotoxic T-cells in both the tumour and the close border around the tumour, as well as increased intra-epithelial infiltration in contrast to MSS tumours. The type of immune cell and the compartment it resides in (intratumoural or intra-epithelial) depend both on MSI status and morphology. Finally, MSI tumours showed a higher angiogenic capacity represented by an increased MVD, hinting for possible therapeutic consequences.

Combining bevacizumab and chemoradiation in rectal cancer. Translational results of the AXEBeam trial.

BACKGROUND: This study characterises molecular effect of bevacizumab, and explores the relation of molecular and genetic markers with response to bevacizumab combined with chemoradiotherapy (CRT). METHODS: From a subset of 59 patients of 84 rectal cancer patients included in a phase II study combining bevacizumab with CRT, tumour and blood samples were collected before and during treatment, offering the possibility to evaluate changes induced by one dose of bevacizumab. We performed cDNA microarrays, stains for CD31/CD34 combined with α-SMA and CA-IX, as well as enzyme-linked immunosorbent assay (ELISA) for circulating angiogenic proteins. Markers were related with the pathological response of patients. RESULTS: One dose of bevacizumab changed the expression of 14 genes and led to a significant decrease in microvessel density and in the proportion of pericyte-covered blood vessels, and a small but nonsignificant increase in hypoxia. Alterations in angiogenic processes after bevacizumab delivery were only detected in responding tumours. Lower PDGFA expression and PDGF-BB levels, less pericyte-covered blood vessels and higher CA-IX expression were found after bevacizumab treatment only in patients with pathological complete response. CONCLUSIONS: We could not support the 'normalization hypothesis' and suggest a role for PDGFA, PDGF-BB, CA-IX and α-SMA. Validation in larger patient groups is needed.

An unsuspected cause of diarrhoea and gastrointestinal bleeding during corticosteroid therapy.

We report on a fatal case of disseminated strongyloidiasis during corticosteroid treatment presenting with abdominal pain, diarrhoea and lower gastrointestinal bleeding. The patient emigrated from Thailand 16 years before the current hospitalisation. Complicated strongyloidiasis is a relatively unrecognized complication of corticosteroid therapy in non-endemic areas. In individuals who have resided in endemic areas, even decades before treatment, strongyloidiasis should be excluded before initiation of immunosuppressants.

Chronic wounds in a kidney transplant recipient with moderate renal impairment.

Calcific uremic arteriolopathy (CUA) or calciphylaxis is a condition predominantly observed in patients with end-stage kidney disease characterized by small vessel calcification, intimal proliferation, endovascular fibrosis and intravascular thrombosis causing down-stream infarction predominantly of skin resulting in extremely painful necrotic ulceration. Several interventions have been proposed in an attempt to attenuate the high mortality associated with CUA. One of the most promising therapeutic approaches is the administration of sodium thiosulfate which is able to chelate cations such as calcium and in this way possibly dissolving tissue calcium deposits into more hydrophilic calcium thiosulfate. Due to the scarcity of reports of CUA patients treated with sodium thiosulfate the safety profile of this drug is not (well) established at this moment especially in patients not receiving kidney replacement therapy. Here, we describe a case of a kidney transplant recipient with CUA and moderately declined kidney function who was treated with sodium thiosulfate and developed important hypernatremia and high anion gap acidosis necessitating significant reduction in dosing.

Gene expression profiling reveals clear differences between EBV-positive and EBV-negative posttransplant lymphoproliferative disorders.

Posttransplant patients are at risk of developing a potentially life-threatening posttransplantation lymphoproliferative disorder (PTLD), most often of diffuse large B cell lymphoma (DLBCL) morphology and associated with Epstein-Barr Virus (EBV) infection. The aim of this study was to characterize the clinicopathological and molecular-genetic characteristics of posttransplant DLBCL and to elucidate whether EBV(+) and EBV(-) posttransplant DLBCL are biologically different. We performed gene expression profiling studies on 48 DLBCL of which 33 arose posttransplantation (PT-DLBCL; 72% EBV+) and 15 in immunocompetent hosts (IC-DLBCL; none EBV+). Unsupervised hierarchical analysis showed clustering of samples related to EBV-status rather than immune status. Except for decreased T cell signaling these cases were inseparable from EBV(-) IC-DLBCL. In contrast, a viral response signature clearly segregated EBV(+) PT-DLBCL from EBV(-) PT-DLBCL and IC-DLBCL cases that were intermixed. The broad EBV latency profile (LMP1+/EBNA2+) was expressed in 59% of EBV(+) PT-DLBCL and associated with a more elaborate inflammatory response compared to intermediate latency (LMP1+/EBNA2-). Inference analysis revealed a role for innate and tolerogenic immune responses (including VSIG4 and IDO1) in EBV(+) PT-DLBCL. In conclusion we can state that the EBV signature is the most determining factor in the pathogenesis of EBV(+) PT-DLBCL.

Subacute cytomegalovirus appendicitis in a renal transplant recipient.

Cytomegalovirus (CMV) infections in transplant patients is a well-known disease. We describe the first case, to our knowledge, documenting CMV appendicitis in a renal transplant patient, and its clinical presentation, diagnosis, and treatment.

Subclinical GvHD in non-irradiated F1 hybrids: severe lymphoid-tissue GvHD causing prolonged immune dysfunction.

GvHD is an important complication of allogeneic hematopoietic SCT. Parent-in-F1 models are frequently used to study GvHD immunobiology; the characteristics of parent-in-F1 GvHD vary between strain combinations and induction protocols. Here, we observed that a high-dose challenge of non-irradiated B6DBA2F1 and B6SJLF1 recipients with C57BL/6 splenocytes left the majority of recipients clinically healthy, while inducing progressive high-grade donor T-cell chimerism. We investigated this previously undescribed pattern of parent-in-F1 T-cell alloreactivity and studied the effect of serial parental splenocyte infusions on epithelial and lymphohematopoietic tissues. The majority of recipients of 4 weekly splenocyte infusions showed long-term survival with gradual establishment of high-grade donor chimerism and without any signs of epithelial-tissue GvHD. A minority of recipients showed BM failure type of GvHD and, respectively, graft rejection. Moreover, long-term F1 chimeras showed protracted pancytopenia, and in peripheral lymphoid tissues severe lymphopenia and near-complete eradication of APCs and dysfunction in antigen-presenting capacity in remaining APC. Hematopoiesis and lymphoid tissue composition recovered only after multilineage donor chimerism had established. In conclusion, we report on a novel type of parent-in-F1 hybrid GvHD, where a cumulative high dose of C57BL/6 parental splenocytes in non-irradiated F1 mice induces subclinical but severe hematolymphoid-tissue GvHD, causing prolonged immuno-incompetence.

Allogeneic bone marrow transplantation and donor lymphocyte infusion in a mouse model of irradiation-induced myelodysplastic/myeloproliferation syndrome (MD/MPS): evidence for a graft-versus-MD/MPS effect.

The role of graft-versus-malignancy reactivity in the effects of allogeneic hematopoietic stem cell transplantation and donor lymphocyte infusion (DLI) for myelodysplastic syndromes is as yet not well established. Clinical data are limited and animal models are scarce. Here, we report on the effects of allogeneic bone marrow transplantation (alloBMT) and DLI in a novel model of irradiation-induced murine myelodysplastic/myeloproliferation syndrome (MD/MPS). Total body irradiation with 8.5 Gy in SJL/J mice gave rise to a lethal wasting syndrome in 60% of mice, characterized by 1 degrees normocellular bone marrow with dysplastic features in erythroid, myeloid and megakaryocytic cell lineages, 2 degrees lymphosplenomegaly with spleens harboring a prominent extramedullary hematopoiesis with erythroid, myeloid and megakaryocytic lineages exhibiting dysplastic features, and foci of dysplastic hematomyelopoiesis in the liver, 3 degrees peripheral thrombocytopenia and 4 degrees evidence of disseminated infection or leukemic transformation in selected animals. This clinicopathological picture was consistent with a murine form of MD/MPS. Syngeneic or allogeneic (BALB/c) T cell-depleted BMT could not prevent the occurrence of lethal MD/MPS. In contrast, DLI at weeks 2-4 after BMT led to restoration of the dysbalanced hematomyelopoiesis. However, severe DLI-induced acute graft-versus-host disease occurred, precluding a survival advantage. We present evidence of the existence of a post-alloBMT DLI-induced graft-versus-MD/MPS effect in murine irradiation-induced MD/MPS.

Posttransplant Epstein-Barr virus-associated myogenic tumors: case report and review of the literature.

Epstein-Barr virus (EBV) has been implicated in the pathogenesis of different types of malignancies. While nonmelanoma skin cancers, lymphomas and Kaposi sarcomas are the most frequently reported malignancies after solid organ transplantation, EBV-associated smooth muscle tumors (EBV-SMT) after transplantation are rare and thus far only 18 cases in kidney recipients have been reported. A case of a 51-year-old kidney transplant recipient diagnosed with EBV-SMT is reported together with a review of the literature.

CTLA-4 blockade in murine bone marrow chimeras induces a host-derived antileukemic effect without graft-versus-host disease.

We studied the effect of CTLA-4 blockade on graft-versus-leukemia and graft-versus-host responses in a mouse model of minor histocompatibility-mismatched bone marrow transplantation. Early CTLA-4 blockade induced acute graft-versus-host disease. Delayed CTLA-4 blockade resulted in a lethal condition with lymphosplenomegaly, but with stable mixed T-cell chimerism, unchanged alloreactive T-cell frequencies and absent anti-host reactivity in vitro. In contrast, multiorgan lymphoproliferative disease with autoimmune hepatitis and circulating anti-DNA auto-antibodies were documented. Splenic lymphocytes exhibited ex vivo spontaneous proliferation and a marked proliferative response against host-type dendritic cells pulsed with syngeneic (host-type) tissue-peptides. Both phenomena were exclusively mediated by host and not donor T cells, supporting an autoimmune pathogenesis. Selectively host-derived T-cell immune reactivity was equally documented against leukemia-peptide-pulsed dendritic cells, and this was paralleled by a strong in vivo antileukemic effect in anti-CTLA-4-treated and subsequently leukemia-challenged chimeras. In conclusion, delayed CTLA-4 blockade induced a host-derived antileukemic effect, occurring in the context of an autoimmune syndrome and strictly separated from graft-versus-host disease. Both antileukemic and autoimmune responses depended on the allogeneic component, as neither effect was seen after syngeneic bone marrow transplantation. Our findings reveal the potential of using CTLA-4 blockade to establish antileukemic effects after allogeneic hematopoietic stem cell transplantation, provided autoimmunity can be controlled.

The dynamics of the B follicle: understanding the normal counterpart of B-cell-derived malignancies.

The repertoire of B cells secreting antibodies with unique antigen-binding specificities is produced at two stages: a primary B-cell repertoire is formed in the bone marrow through immunoglobulin gene rearrangements, whereas a secondary B-cell repertoire is generated in the peripheral lymphoid organs (spleen, lymph nodes and mucosa-associated lymphoid tissue) through somatic hypermutation and class-switch recombination upon antigen encounter. The latter events take place within highly specialized histological structures, designated B follicles, which are composed of distinct microanatomical compartments namely the follicle centre, lymphocytic corona and marginal zone. Each compartment comprises a particular subset of B cells, characterized by unique properties, thereby reflecting the complexity and variability in the spectrum of defence mechanisms against invading pathogens. The past years have spawned an avalanche of new data and information that encompasses both the structure and function of each compartment and its B cells. This review incorporates up-to-date information on peripheral B-cell differentiation into a challenging working model, thereby pointing to the structural and functional imprint of both the T-cell-dependent and T-cell-independent immune response on the B follicle. As such, this article aims to form an excellent base for a better understanding of the normal counterpart of B-cell-derived haematological malignancies (leukemias and lymphomas).

The pathogenesis of MALT lymphomas: where do we stand?

Mucosa-associated lymphoid tissue (MALT) lymphoma is a heterogeneous form of a B-cell non-Hodgkin's lymphoma with extranodal location. The gastrointestinal tract is the most common site of disease, but involvement of multiple other organ systems has been documented. Four translocations, t(11;18)(q21;q21), t(1;14)(p22;q32), t(14;18)(q32;q21) and t(3;14)(p13;q32), are specifically associated with MALT lymphoma. Remarkably, the genes targeted by at least three of these translocations are involved in one and the same pathway, leading to the activation of nuclear factor-kappaB (NF-kappaB). This review presents MALT lymphoma as a model of how sustained inflammation increases the risk of genotoxic insults and how these genetic events initiate oncogenesis.