Duodenal follicular lymphoma lacks AID but expresses BACH2 and has memory B-cell characteristics

Duodenal-type follicular lymphoma: comprehensive insights into disease characteristics and established treatment strategies

PURPOSE OF REVIEW

This review aims to detail the characteristics and outcomes of duodenal-type follicular lymphoma (DTFL), a rare lymphoma variant. It focuses on integrating recent reports in treatment modalities and highlights emerging insights into the unique biological features of the disease.

RECENT FINDING

Recent studies confirm the indolent nature of DTFL, with extended follow-up periods showing favorable outcomes under watchful waiting strategies and a notable proportion of patients experiencing spontaneous remission. Additionally, advancements in understanding the disease's biology revealed that the tumor microenvironment is marked by specific genomic expressions indicative of chronic inflammation.

SUMMARY

The observations of spontaneous resolution and the generally favorable progression of DTFL call for a conservative approach in initiating treatment. Clinical management should judiciously consider the disease's typically benign course against the potential risks of intervention, promoting customized treatment protocols tailored for cases with clinical necessity. Additionally, the discovery of an inflammatory tumor microenvironment and molecular evidence suggesting an antigen-driven process highlight critical areas for future research.

Bridging Clinicopathologic Features and Genetics in Follicular Lymphoma: Towards Enhanced Diagnostic Accuracy and Subtype Differentiation

Follicular lymphoma (FL) is a neoplasm that originates from germinal center B cells and typically forms at least a partial follicular pattern. Approximately 85% of FL cases harbor the t(14;18)(q32;q21)/IGH::BCL2 which leads to the overexpression of BCL2. These cases are referred to as classic FL in the current World Health Organization classification [1]. These neoplasms often exhibit hallmark epigenetic deregulation due to recurrent mutations in genes such as KMT2D, CREBBP, and EZH2, with KMT2D and CREBBP considered founding events in FL lymphomagenesis. In contrast, about 15% of FL cases are negative for the t(14;18), which could present diagnostic challenges. These cases may lack the typical genetic markers and require careful pathological and molecular analysis for accurate diagnosis. This review aims to provide an up-to-date pathology resource on FL, focusing on the pathological and molecular characteristics of these neoplasms. We will detail the diagnostic criteria for FL and emphasize the importance of genetic and mutational analyses in accurately characterizing and distinguishing FL subtypes. Furthermore, we will propose methodologies and best practices for the diagnostic work-up of FL to enhance diagnostic accuracy.

Cell cross talk within the lymphoma tumor microenvironment: follicular lymphoma as a paradigm

ABSTRACT

Follicular lymphoma (FL) is an indolent yet incurable germinal center B-cell lymphoma retaining a characteristic follicular architecture. FL tumor B cells are highly dependent on direct and indirect interactions with a specific and complex tumor microenvironment (TME). Recently, great progress has been made in describing the heterogeneity and dynamics of the FL TME and in depicting how tumor clonal and functional heterogeneity rely on the integration of TME-related signals. Specifically, the FL TME is enriched for exhausted cytotoxic T cells, immunosuppressive regulatory T cells of various origins, and follicular helper T cells overexpressing B-cell and TME reprogramming factors. FL stromal cells have also emerged as crucial determinants of tumor growth and remodeling, with a key role in the deregulation of chemokines and extracellular matrix composition. Finally, tumor-associated macrophages play a dual function, contributing to FL cell phagocytosis and FL cell survival through long-lasting B-cell receptor activation. The resulting tumor-permissive niches show additional layers of site-to-site and kinetic heterogeneity, which raise questions about the niche of FL-committed precursor cells supporting early lymphomagenesis, clonal evolution, relapse, and transformation. In turn, FL B-cell genetic and nongenetic determinants drive the reprogramming of FL immune and stromal TME. Therefore, offering a functional picture of the dynamic cross talk between FL cells and TME holds the promise of identifying the mechanisms of therapy resistance, stratifying patients, and developing new therapeutic approaches capable of eradicating FL disease in its different ecosystems.

Frequent CDKN2B/P15 and DAPK1 methylation in duodenal follicular lymphoma is related to duodenal reactive lymphoid hyperplasia

Duodenal type follicular lymphoma (DFL), a rare entity of follicular lymphoma (FL), is clinically indolent and is characterized by a low histological grade compared with nodal follicular lymphoma (NFL). Our previous reports revealed that DFL shares characteristics of both NFL and mucosa-associated lymphoid tissue (MALT) lymphoma in terms of clinical and biological aspects, suggesting its pathogenesis may involve antigenic stimulation. In contrast to NFL, the genomic methylation status of DFL is still challenging. Here, we determined the methylation profiles of DNAs from patients with DFL (n = 12), NFL (n = 10), duodenal reactive lymphoid hyperplasia (D-RLH) (n = 7), nodal reactive lymphoid hyperplasia (N-RLH) (n = 5), and duodenal samples from normal subjects (NDU) (n = 5) using methylation specific PCR of targets previously identified in MALT lymphoma (CDKN2B/P15, CDKN2A/P16, CDKN2C/P18, MGMT, hMLH-1, TP73, DAPK, HCAD). DAPK1 was frequently methylated in DFL (9/12; 75%), NFL (9/10; 90%), and D-RLH (5/7; 71%). CDKN2B/P15 sequences were methylated in six DFL samples and in only one NFL sample. Immunohistochemical analysis showed that p15 expression inversely correlated with methylation status. Genes encoding other cyclin-dependent kinase inhibitors (CDKN2A/P16, CDKN2C/P18) were not methylated in DFL samples. Methylation of the genes of interest was not detected in DNAs from D-RLH, except for DAPK1, and the difference in the extent of methylation between NDU and D-RLH was statistically significant (P = 0.013). Our results suggest that D-RLH serves as a reservoir for the development of DFL and that methylation of CDKN2B/P15 plays an important role in this process.

Pathogenesis of Gastrointestinal Follicular Lymphomas: Consideration Based on Histopathology and Endoscopic Findings

Gastrointestinal (GI) follicular lymphoma (FL) is the most frequently diagnosed extranodal FL; however, its pathogenesis is debatable. We investigated the distribution, endoscopic, and histopathologic findings of 366 GI FL samples obtained from 298 patients. FLs were most frequently observed in the small intestine (71%), including the duodenum (52%), but were also commonly found in the stomach (15%) and colon (12%). The proportion of granular lesions in the duodenum, terminal ileum, colon, and stomach was 74%, 39%, 24%, and 0%, respectively. Submucosal or ulcerated tumors were frequently observed in the stomach (48%) and colon (52%). Most GI FL showed grade 1 to 2 histology (89%) as well as CD10 + (93%) and BCL2 + (98%) positivity. There were no significant differences in the endoscopic or histologic findings between primary and secondary GI FLs. As known, the mucosa of the small intestine is thin and villous, while the mucosa of the stomach and colon is thicker and has a smooth surface. Granular lesions corresponding to very small FL were detected in the former but rarely in the latter. Nine (7%) patients with primary GI FL developed histologic transformation to diffuse large B-cell lymphoma (n=8) or high-grade B-cell lymphoma (n=1) 10 months to 14 years after the diagnosis of FL. Two patients died of lymphoma. In conclusion, the incidence and endoscopic findings differed, but the histopathology was similar in FLs in each site. These differences might be attributed to variations in each GI site's mucosal structure and the neoplastic follicles' size. Due to its characteristic structure, very small classic FLs might be detectable mainly in the small intestine.

Follicular Lymphoma in the 5th Edition of the WHO-Classification of Haematolymphoid Neoplasms-Updated Classification and New Biological Data

The conceptual description of Follicular lymphoma (FL) in the 5th edition of the World Health Organization (WHO) classification of haematolymphoid tumors (WHO-HAEM5) has undergone significant revision. The vast majority of FL (85%) with a follicular growth pattern are composed of centrocytes and centroblasts, harbor the t(14;18)(q32;q21) translocation and are now termed classic FL (cFL). They are set apart from three related subtypes, FL with predominantly follicular growth pattern, FL with unusual cytological features (uFL) and follicular large B-cell lymphoma (FLBCL). In contrast to the revised 4th edition of the WHO classification of haematolymphoid tumors (WHO-HAEM4R), grading of cFL is no longer mandatory. FL with a predominantly diffuse growth pattern had been previously recognized in WHO-HAEM4R. It frequently occurs as a large tumor in the inguinal region and is associated with CD23 expression. An absence of the IGH::BCL2 fusion and frequent STAT6 mutations along with 1p36 deletion or TNFRSF14 mutation is typical. The newly introduced subtype of uFL includes two subsets that significantly diverge from cFL: one with "blastoid" and one with "large centrocyte" variant cytological features. uFL more frequently displays variant immunophenotypic and genotypic features. FLBCL is largely identical to WHO-HAEM4R FL grade 3B and renaming was done for reasons of consistency throughout the classification. In-situ follicular B-cell neoplasm, pediatric-type FL, duodenal-type FL and primary cutaneous follicle center lymphoma are categorized as discrete entities. In addition, novel findings concerning underlying biological mechanisms in the pathogenesis of early and systemic follicular lymphoma will be presented.

Precursory or early lesions of follicular lymphoma: clinical features, pathology, and genetics

Follicular lymphoma (FL) is an indolent B-cell lymphoma with a germinal center (GC) B cell phenotype that typically harbors t(14;18)(q32;q21). t(14;18) juxtaposes IGH on 14q32 and BCL2 on 18q21, resulting in overexpression of the anti-apoptotic BCL2 protein. However, t(14;18) is also found in the peripheral blood or lymphoid nodes (LNs) of otherwise healthy individuals. Moreover, overt FL has several additional gene alterations involved in epigenetic modification, JAK/STAT signaling, immune modulation, and NF-κB signaling, indicating multi-step lymphomagenesis in FL. There are two early or precursory lesions of FL: t(14;18)-positive cells in the peripheral blood of otherwise healthy individuals and in situ follicular B-cell neoplasm (ISFN). t(14;18)-positive cells are found in 10%-50% of healthy populations, and their incidence and frequency increase with age. The detection of t(14;18) in peripheral blood is a predictive factor for an increased risk of overt FL development. In contrast, ISFN is a histopathologically recognizable precursory lesion, in which t(14;18)-positive cells are confined to the GC of otherwise reactive LNs. ISFN is usually detected incidentally, with an incidence ranging from 2.0% to 3.2%. Occasional ISFN cases have concurrent or metachronous clonally related overt FL or aggressive B-cell lymphoma of a GC phenotype. t(14;18)-positive cells in peripheral blood and isolated ISFN, by themselves, are asymptomatic with limited clinical significance; however, investigations of t(14;18)-positive precursory or early lesions offer meaningful insights into the pathogenesis of FL. This review summarizes the epidemiology, clinical features, pathology, and genetics of precursory or early lesions of FL.

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.

Density and size of lymphoid follicles are useful clues in differentiating primary intestinal follicular lymphoma from intestinal reactive lymphoid hyperplasia

Background

Primary intestinal follicular lymphoma (PI-FL) is a rare and indolent lymphoma and is challenging for diagnosis with endoscopic biopsy specimens. Whole slide imaging (WSI) has been increasingly used for assisting pathologic diagnosis, but not for lymphoma yet, probably because there are usually too many immunostained sections in a single case. In this study we attempted to identify morphological clues of PI-FL in the endoscopic biopsy specimens by measuring various parameters using WSI.

Methods

We retrospectively investigated 21 PI-FL cases, and scanned the HE sections from 17 of these cases with endoscopic biopsy specimens. Sections from 17 intestinal biopsies showing reactive lymphoid hyperplasia were scanned for comparison. The density and diameter of lymphoid follicles and the shortest distance of these follicles to the surface epithelia were measured on WSI. Comparisons of the aforementioned parameters were made between the neoplastic and reactive follicles.

Results

The density of follicles was significantly higher in PI-FL than that of reactive hyperplasia (median 0.5 vs. 0.2/mm²; p < 0.01). Furthermore, the neoplastic follicles were significantly larger (median diameter 756.9 vs. 479.7 μm; p < 0.01). The shortest distance of follicles to the surface epithelia tended to be closer in PI-FL (104.7 vs. 177.8 μm, p = 0.056), but not statistically significant.

Conclusions

In this study we found that in PI-FL the density and diameter of lymphoid follicles as measured from WSI were significantly different from that of intestinal reactive lymphoid hyperplasia. When facing the diagnostic challenge between these two entities in routine practice, pathologists might be alerted by these morphological clues and request for immunohistochemistry for differential diagnosis.

What do we know about duodenal-type follicular lymphoma? From pathological definition to treatment options

Duodenal-type follicular lymphoma (DFL) is a newly recognised variant of follicular lymphoma (FL), although little is known about its biology and clinical evolution. In general, patients tend to have mild symptoms and do not require therapy, comparable with other forms of low-tumour burden asymptomatic FL. Specific pathological features, such as a dendritic cell meshwork, low expression of CD10 and upregulation of activation-induced cytidine deaminase can help the diagnosis. The molecular landscape of DFL is similar to the classical nodal presentation of FL, although studies using gene expression profiling demonstrate a close relation with MALT lymphomas. Markers associated with inflammation have suggested that the microenvironment plays a likely role in the pathogenesis of DFL and its low progression rate. Clinical series published vary between 20-63 patients with an estimated overall survival between 92-100% and a median follow-up ranging between 20 and 107 months. Treatment options include a watch and wait strategy, rituximab monotherapy and radiotherapy. In this review, we summarise current pathological data and treatment studies in DFL.

Update on lymphoproliferative disorders of the gastrointestinal tract: disease spectrum from indolent lymphoproliferations to aggressive lymphomas

This paper summarizes two sessions of the workshop during the XIX meeting of the European Association for Haematopathology (EAHP) held in Edinburgh in September 2018 dedicated to lymphomas of the gastrointestinal tract. The first session focused on the clinical and pathological features of primary gastrointestinal T cell and NK-cell lymphoproliferative disorders. The distinction between precursor lesions (RCD type 2) and enteropathy-associated T cell lymphoma were stressed, including the discussion of new diagnostic markers for the identification of aberrant phenotypes. Indolent T cell lymphoproliferative disorders of the gastrointestinal tract cases showed phenotypic heterogeneity with novel molecular alterations in few cases, such as STAT3-JAK2 fusion. In addition, novel clonal markers of disease, such as AXL and JAK3 somatic variants support the neoplastic nature of NK-cell enteropathy. The session on gastrointestinal tract B cell lymphoproliferations was dedicated to B cell lymphoproliferative disorders that arise primarily in the gastrointestinal tract (i.e., duodenal-type follicular lymphoma) or preferentially involve the digestive tract, such as large B cell lymphoma with IRF4 translocation and mantle cell lymphoma (MCL), including diverse molecular subtypes (i.e., CCND3-positive MCL mimicking MALT lymphoma). Challenging cases of high-grade B cell lymphomas with complex genetic profiles demonstrated the usefulness of novel molecular diagnostic methods such as targeted NGS to identify high-risk genetic features with potential clinical impact.

Duodenal-Type Follicular Lymphoma: A Clinicopathologic Review

Duodenal-type follicular lymphoma (D-FL) is a newly recognized entity in the 2016 World Health Organization classification update. It has an immunophenotype similar to that of other FLs and usually carries the typical t(14;18)(q32;q21) translocation. However, unlike other FLs, D-FL is almost always diagnosed at a low stage and stays localized to the small intestine, most commonly the second portion of the duodenum, whereas the vast majority of other FLs are diagnosed at an advanced stage. Additionally, D-FL gene expression and pathogenesis appear to be more closely related to extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue than to other types of FL. Therefore, many oncologists have opted to treat this variant of FL in a "watch and wait" manner because of its excellent prognosis and the rarity of D-FL to progress even when no treatments are attempted.

Gastrointestinal follicular lymphoma: Current knowledge and future challenges

The gastrointestinal (GI) tract is the most commonly involved site of extranodal follicular lymphoma (FL). GI-FL shows very indolent clinical behavior and localized at GI tract without any progression or transformation compared to nodal FL. The most frequently involved site of the GI tract was the duodenum followed by the jejunum and ileum, and only 15% of FL arising in the second part of the duodenum were localized there without scattered very small daughter lesions in other GI tract examined by double-balloon endoscopy. The typical macroscopic appearance of GI-FL was multiple white nodules. Microscopically, neoplastic cells were small- to medium-sized lymphoid cells and formed neoplastic follicles. Most of the cases (>95%) were histologically Grade 1 to 2 (low grade). Several pathological and molecular characteristics were seen in GI-FL (especially duodenal FL) compared with nodal FL: immunoglobulin heavy chain deviation to VH4 and VH5; memory B-cell immunophenotype; and molecular features shared by mucosa-associated lymphoid tissue lymphoma. Considering the pathological and molecular uniqueness of this disease, GI-FL should be separately managed from nodal FL.

Watch-and-wait policy versus rituximab-combined chemotherapy in Japanese patients with intestinal follicular lymphoma

BACKGROUND AND AIM

Few reports have demonstrated the effectiveness of treatments for intestinal follicular lymphoma (FL) because of the limited number of patients who undergo comprehensive small intestinal examinations. This study compared the efficacy of rituximab-combined chemotherapy in patients with asymptomatic and low tumor burden (LTB) intestinal FL, according to the criteria of the Groupe d'Etude des Lymphomes Folliculaires, with that of a "watch and wait" (W&W) approach.

METHODS

The endoscopic examination for entire gastrointestinal tracts was performed in 29 Japanese patients with intestinal FL. These patients had CD21-positive follicular dendritic cells arranged in a duodenal pattern. In a prospective, two-center, open-label trial, this study evaluated the efficacy of rituximab-combined chemotherapy ([cyclophosphamide, doxorubicin, vincristine, and prednisone] or [cyclophosphamide, vincristine, and prednisone]) and prolonged treatment with rituximab (R-Chemo+prolongedR) in 14 patients and compared their outcomes with those of 15 patients managed with a W&W approach.

RESULTS

Four patients managed with the W&W plan showed worsening macroscopic findings, lesion area enlargement, or clinical stage progression but stayed on this plan because they had LTB and experienced no changes in bowel function. In the R-Chemo+prolongedR group, all patients achieved complete remission; recurrence occurred in one patient, who was subsequently managed with the W&W plan because of LTB. There were no significant differences in progression-free survival between the two groups (P = 0.1045). Overall survival was 100% in both groups.

CONCLUSIONS

The prognoses of patients with asymptomatic intestinal FL and LTB who were managed with a W&W strategy were comparable with those of patients receiving R-Chemo+prolongedR.

Gastric follicular lymphoma: A report of 3 cases and a review of the literature

Follicular lymphoma (FL) occurs primarily in the gastrointestinal tract, with the stomach being one of the rarest sites. According to the literature, <20 cases of primary gastric FL have been reported, with the number of cases with detailed pathological descriptions being even less. The aim of the present study was to compare clinicopathological features of gastric FL with FL at alternative sites. A total of 3 cases of gastric FL were retrieved from among 3,216 cases in the databases of 4 university hospitals in South Korea: Seoul National University (SNU) Hospital, SNU Boramae Hospital, SNU Bundang Hospital (all Seoul, South Korea) and Dongtan Sacred Heart Hospital Hallym University (Dongtan, South Korea), including 2 primary cases and 1 case that was possibly secondary to nodal FL. The 2 primary gastric FL cases were incidentally detected in routine health check-ups. An endoscopy revealed a single polypoid submucosal mass and biopsies failed to confirm the diagnosis due to minimal mucosal involvement. Therefore, a partial gastrectomy was performed. The epicenters of the tumors were submucosal, with focal extension to the muscularis propria. However, 1 case exhibited an isolated FL nodule in the omentum. Histopathological examination revealed FL of grade 1–2 with a follicular pattern and with strong expression of germinal center markers and B-cell lymphoma 2 (BCL2). Rearrangement of BCL2 was not identified using fluorescence in situ hybridization studies in 2 cases. In contrast to these 2 cases, the remaining FL case was confirmed with an endoscopic biopsy. The endoscopy revealed multiple eroded polypoid lesions, and pathology revealed FL of grade 1–2 with a predominantly diffuse pattern, and with immunoglobulin heavy chain IGH/BCL2 translocation. In view of the extensive lymphadenopathy, the last case possibly presented as secondary involvement of nodal FL. It is challenging to diagnose FL in the stomach due to little mucosal involvement, as well as the unfamiliarity of the tumor due to its rarity. However, the results of the present study suggest that primary gastric FL may exhibit unique pathological features, including a predominantly follicular pattern and an absence of BCL2 rearrangement.

Pathogenesis of follicular lymphoma

Follicular lymphoma (FL) is presented as a germinal centre B cell lymphoma that is characterized by an indolent clinical course, but remains - paradoxically - largely incurable to date. The last years have seen significant progress in our understanding of FL lymphomagenesis, which is a multi-step process beginning in the bone marrow with the hallmark t(14;18)(q32;q21) translocation. The pathobiology of FL is complex and combines broad somatic changes at the level of both the genome and the epigenome, the latter evidenced by highly recurrent mutations in chromatin-modifying genes such as KMT2D and CREBBP. While the importance of the FL microenvironment has since long been well understood, it has become evident that somatic lesions within tumour cells re-educate normal immune and stromal cells to their advantage. Enhanced understanding of FL pathogenesis is currently leading to refined therapeutic targeting of perturbed biology, paving the way for precision medicine in this lymphoma subtype.

Lymphoproliferative Disorders of the Gastrointestinal Tract

CONTEXT

- The diagnosis of gastrointestinal lymphoproliferative disorders can be challenging because of the small size of biopsies and the wide spectrum of lymphoproliferative disorders that may be encountered.

OBJECTIVE

- To review the spectrum of lymphoproliferative disorders involving the gastrointestinal tract, highlighting potential pitfalls.

DATA SOURCES

- Peer-reviewed articles and clinical experience.

CONCLUSIONS

- Interpretation of lymphoid infiltrates in gastrointestinal biopsies requires synthesis of morphologic, immunophenotypic, molecular genetic, and clinical information. Knowledge of indolent lymphoproliferative disorders that may mimic aggressive lymphomas will help in preventing misdiagnoses.

Comparison of clinicopathologic characteristics of gastric follicular lymphomas and duodenal follicular lymphomas

We compared the incidence, esophagogastroduodenoscopy (EGD) findings, and histopathologic characteristics of gastric and duodenal follicular lymphomas (FL). Of 626 FL cases, primary gastric FL and secondary gastric involvement of FL were observed in 1% and 5% of the cases, respectively, which were lower incidences than duodenal FL (10% and 9%, respectively). Gastric FL usually appeared as submucosal tumors (primary, 71%; secondary, 79%), whereas duodenal FL, as granular lesions (primary, 92%: secondary, 87%). In the granular duodenal lesions, the neoplastic follicles were located sparsely on the muscularis mucosa and could be found between villi, whereas in the stomach, similar lesions were hidden within the lamina propria, and only larger lesions such as submucosal tumors could be detected on the mucosal surface. The differences in the incidences and EGD findings were considered to be associated with structural differences of the lamina propria. Typical FL features: grades 1-2 histology, follicularity, and CD10⁺ and/or BCL6⁺ and BCL2⁺ were usually observed in all primary and secondary gastric and duodenal FL. Gastroduodenal and bone marrow involvement were found in 12% and 33% of the cases, respectively, and there was no significant correlation between them (P=.095). Twenty-nine cases (5%) were up-staged by gastroduodenal-positive results. In conclusion, the histopathology of gastric FL was similar to that of duodenal and nodal FL; the differences in the incidence and EGD findings between gastric and duodenal FL were considered to be associated with structural difference of the lamina propria, and EGD was useful as a staging procedure.

CD10 down expression in follicular lymphoma correlates with gastrointestinal lesion involving the stomach and large intestine

Follicular lymphoma (FL) shows co-expression of B-cell lymphoma 2 (BCL2) and CD10, whereas downexpression of CD10 is occasionally experienced in gastrointestinal (GI) FL with unknown significance. Gastrointestinal FL is a rare variant of FL, and its similarity with mucosa-associated lymphoid tissue lymphoma was reported. We investigated the clinicopathological and genetic features of CD10 downexpressed (CD10^down ) GI-FL. The diagnosis of CD10^down FL was carried out with a combination of pathological and molecular analyses. The incidence of CD10^down GI-FL was shown in 35/172 (20.3%) cases, which was more frequent than nodal FL (3.5%, P < 0.001). The difference was additionally significant between GI-FL and nodal FL when the analysis was confined to primary GI-FL (55.2% vs 3.5%, P < 0.001). Compared to CD10⁺ GI-FL, CD10^down GI-FL significantly involved the stomach or large intestine (P = 0.015), and additionally showed the downexpression of BCL6 (P < 0.001). The follicular dendritic cell meshwork often showed a duodenal pattern in the CD10^down group (P = 0.12). Furthermore, a lymphoepithelial lesion was observed in 5/12 (40%) gastric FL cases, which indicated caution in the differentiation of mucosa-associated lymphoid tissue lymphoma. Molecular analyses were undertaken in seven cases of CD10^down GI-FL, and an identical clone was found between CD10^down follicles and CD10⁺ BCL2⁺ neoplastic follicles. In the diagnosis of cases with CD10^down BCL2⁺ follicles, careful examination with molecular studies should be carried out.

Protocadherin γ A3 is expressed in follicular lymphoma irrespective of BCL2 status and is associated with tumor cell growth

Protocadherin genes (PCDHs) have been suggested to act as tumor suppressor genes in various tumor types. Previous studies have demonstrated the upregulation of certain PCDH-γ subfamily genes in nodal and duodenal follicular lymphoma (FL) using gene expression analyses. However, the mechanisms and associated molecular function of PCDH-γ subfamily gene upregulation in FL remain to be elucidated. The present study examined the expression of PCDHGA3, an upregulated PCDH-γ gene subfamily member, in B-cell lymphoma 2 (BCL2)-positive and -negative FL, and evaluated its association with tumor cell proliferation in an FL-derived cell line. Immunohistochemical analysis demonstrated that the majority of FL grade 1–2 samples (19/20; 95%) and over half of grade 3A FL samples (5/9; 56%) were PCDHGA3-positive, whereas only 1/17 reactive lymphoid hyperplasia samples was positive. Notably, this positivity was widely observed in samples of BCL2-negative FL (13/15; 87%) and FL with diffuse area (10/10; 100%). The FL-derived cell line FL18 exhibited strong PCDHGA3 expression, similar to the patient samples, and its proliferation was suppressed by PCDHGA3 gene knockdown. Genes expressed concomitantly with PCDHGA3 were selected from gene expression data, and TNFRSF6B, a member of the tumor necrosis factor receptor superfamily, was among the top five most strongly correlated genes. Coexpression of TNFRSF6B and PCDHGA3 was observed immunohistochemically in FL18 cells, suggesting potential cooperation in tumor cell maintenance. In conclusion, the results of the present study indicated that PCDHGA3 was expressed in FL irrespective of BCL2 status and grading and was associated with cell proliferation. Further studies involving molecular genetic analyses are required to elucidate the mechanisms underlying the activity of PCDHGA3 in FL.

Gastrointestinal follicular lymphoma: using primary site as a predictor of survival

Gastrointestinal follicular lymphoma (GI‐FL) is a rare extranodal variant of follicular lymphoma (FL) that has been increasingly reported in the literature. An especially indolent course is linked to the disease after a lack of observed patient death in past studies. However, overall survival (OS) and associated prognostic factors remain unclear. A large population‐based database was utilized to identify demographic and clinicopathologic characteristics of GI‐FL, along with survival differences among primary sites. The Surveillance, Epidemiology, and End Results Registry was used to identify GI‐FL cases between the years of 1973 and 2012. Kaplan–Meier curves compared OS differences and Cox proportional hazard models analyzed prognostic factors. Final analysis included 1109 cases. Small intestinal cases, which included those with single‐site and multi‐segment involvement, were most common (63.6%) followed by gastric (18.2%) and colorectal cases (18.2%). Small intestinal GI‐FL presented more frequently with grade I histology, and less often with grade III histology (P < 0.001 and P < 0.001, respectively). Small intestinal cases had better outcomes (5‐year OS = 80.9%, P < 0.001) compared to cases involving the stomach (5‐year OS = 52.7%) and colorectum (5‐year OS = 71.5%). On multivariate analysis for predictors of mortality, small intestinal involvement predicted for better survival; hazard ratio (HR) 0.66 (95% CI: 0.51–0.85). Advanced age (≥66), grade (grade III), and stage (Ann Arbor Stage III/IV) predicted for mortality with HR 5.46 (95% CI: 3.80–7.84), 1.42 (95% CI: 1.10–1.83), 1.57 (95% CI: 1.15–2.16), respectively. GI‐FL has poorer outcomes than previously suggested. Small intestinal involvement has a better prognosis. A possible biological basis for this will require further investigations in the future.

Radiation therapy for localized duodenal low-grade follicular lymphoma

The aim of this study was to evaluate the initial treatment results and toxicities of radiation therapy for patients with early stage low-grade follicular lymphoma (FL) arising from the duodenum. We reviewed 21 consecutive patients with early stage duodenal FL treated with radiation therapy between January 2005 and December 2013 at the Cancer Institute Hospital, Tokyo. The characteristics of patients were: median age 62 years (range, 46-79 years), gender (male, 6; female, 15), clinical stage (I, 20; II1, 1), histological grade (I, 17; II, 4). All patients were treated with radiation therapy alone. The median radiation dose was 30.6 Gy (range, 30.6-39.6) in 17 fractions. The involved-site radiation therapy was delivered to the whole duodenum. The median follow-up time was 43.2 months (range 21.4-109.3). The 3-year overall survival (OS), relapse-free survival (RFS) and local control (LC) rates were 94.7%, 79.3% and 100%, respectively. There were four relapses documented outside the treated volumes: two in the gastrointestinal tract (jejunum, terminal ileum), one in an abdominal lymph node (mesenteric lymph node) and one in the bone marrow. None died of the disease; one death was due to acute myeloid leukemia. No toxicities greater than Grade 1 were observed during treatment and over the follow-up time. The 30.6 Gy of involved-site radiation therapy provided excellent local control with very low toxicities. Radiation therapy could be an effective and safe treatment option for patients with localized low grade FL arising from the duodenum.

The 2016 revision of the World Health Organization classification of lymphoid neoplasms

A revision of the nearly 8-year-old World Health Organization classification of the lymphoid neoplasms and the accompanying monograph is being published. It reflects a consensus among hematopathologists, geneticists, and clinicians regarding both updates to current entities as well as the addition of a limited number of new provisional entities. The revision clarifies the diagnosis and management of lesions at the very early stages of lymphomagenesis, refines the diagnostic criteria for some entities, details the expanding genetic/molecular landscape of numerous lymphoid neoplasms and their clinical correlates, and refers to investigations leading to more targeted therapeutic strategies. The major changes are reviewed with an emphasis on the most important advances in our understanding that impact our diagnostic approach, clinical expectations, and therapeutic strategies for the lymphoid neoplasms.

The Expanding Spectrum of Follicular Lymphoma

Follicular lymphoma is a far more heterogeneous entity than originally appreciated. Clinical and biological variants are increasingly more granularly defined, expanding the spectrum of disease. Some variants associate with age, whereas others with anatomic site. Identification of these biologically distinct diseases has real prognostic and predictive value for patients today and likely will be more relevant in the future. Understanding of follicular lymphoma precursors has also made their identification both scientifically and clinically relevant. This review summarizes the features and understanding of follicular lymphoma, variants, and precursor lesions.

Diagnosis of follicular lymphoma of the gastrointestinal tract: A better initial diagnostic workup

Due to an increasing incidence and more frequent recognition by endoscopists, gastrointestinal follicular lymphoma has been established as a variant of follicular lymphoma. However, due to its rarity, there are no established guidelines on the optimal diagnostic strategy for patients with primary gastrointestinal follicular lymphoma or secondary gastrointestinal involvement of systemic follicular lymphoma. This review offers an overview and pitfalls to avoid during the initial diagnostic workup of this disease entity. Previously reported case reports, case series, and retrospective studies are reviewed and focus on the disease's endoscopic and histological features, the roles of computed tomography and positron emission tomography scanning, the clinical utility of the soluble interleukin-2 receptor, and the possible pathogenesis.

Colorectal Manifestation of Follicular Lymphoma

OBJECTIVE

Due to their rarity, the endoscopic features and clinical backgrounds of colorectal follicular lymphoma lesions have not yet been fully investigated. The aim of this study was to reveal the characteristics of this disease entity.

METHODS

A database search performed at the Department of Pathology of our institute identified 12 follicular lymphoma patients with involvement in the cecum, colon, and/or rectum. Data regarding the endoscopic, radiological, biological, and pathological examinations performed were retrospectively reviewed from their clinical records.

RESULTS

The mean age of the patients (5 men, 7 women) was 58.7 years. Five patients were classified as being Lugano system stage I, while the other seven patients were stage IV. In all of the patients, colorectal follicular lymphoma presented with papular (n=4), polypoid (n=4), and flat elevated lesions (n=4). No erosions or ulcers were seen in any of the lesions. The initial pathological diagnoses included extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (n=2) and colitis/proctitis with infiltration of inflammatory cells (n=3), in addition to the correct diagnosis of follicular lymphoma (n=7).

CONCLUSION

Colorectal involvement of follicular lymphoma shows no erosions or ulcers. These lesions could be macroscopically observed as papular, polypoid and flat elevated lesions. Making a correct diagnosis of this disease based on the findings of biopsied samples is sometimes challenging. In such cases, multiple biopsies and/or endoscopic mucosal resection is required, in addition to appropriate consultation with pathologists.

Elevation of serum interleukins 8, 4, and 1β levels in patients with gastrointestinal low-grade B-cell lymphoma

Proinflammatory cytokines that are produced by helper T cells (Th) regulate immune reactions, facilitate class switching of B cells, and prolong the lifespan of B and T cells. Eradication therapy using antibiotics is sometimes effective against gastrointestinal (GI) malignant lymphoma, suggesting that the tumor development or progression is affected by the inflammatory microenvironment. In the present study, serum samples from 148 patients with various subtypes of malignant lymphoma were tested for 11 proinflammatory Th1/Th2 cytokines. In the comparison by subtype or GI lesions, serum interleukin (IL)-8 (P = 6.7E−05), IL-4 (P = 7.5E−05), and IL-1β (P = 0.0043) levels showed significant differences among subtypes, being particularly elevated in follicular lymphomas (FL) and mucosa-associated lymphoid tissue (MALT) lymphomas. Serum IL-8 levels were elevated in GI-FL and MALT lymphomas, and serum IL-4 and IL-1 β levels were elevated in MALT lymphomas. These findings show that GI low-grade B-cell lymphoma could develop against the background of an inflammatory microenvironment. Thus, these cytokines may be useful as diagnostic markers and could provide new insights into tumor development.

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.

A multicenter survey of enteroscopy for the diagnosis of intestinal follicular lymphoma

The importance of enteroscopy examinations to investigate the entire length of the small intestines has been emphasized in follicular lymphoma patients with intestinal involvement. The aim of the present study was to determine the current state of enteroscopy examinations, including the performance rate, and the prevalence of small intestinal lesions in a patient population in Japan. A retrospective multicenter survey of 17 institutions collected the case information of 110 follicular lymphoma patients with gastrointestinal involvement. The results of the enteroscopy examinations were reviewed, and in order to identify potential factors affecting the performance rate of enteroscopy, patient gender, age at lymphoma diagnosis, histopathological grade, clinical stage, the date of the initial diagnosis and the annual volume of enteroscopy at the institution were compared between the patients who underwent one or more enteroscopy procedures and the patients who did not undergo enteroscopy. A total of 34 patients (30.9%) underwent enteroscopy, and 24 of these (70.6%) presented with involvement in the jejunum and/or ileum. It was found that more patients diagnosed in recent years and more patients treated at an ultra-high volume institution (≥101 enteroscopy examinations/year) underwent an enteroscopy. In conclusion, although the prevalence of small intestinal lesions was high (70.6%) in the follicular lymphoma patients presenting with intestinal involvement, the performance rate of enteroscopy was only 30.9%, and thus the majority of the patients have not undergone enteroscopy examinations. Further investigation is required to define the clinical significance of enteroscopy at the initial diagnostic work-up and during the follow-up period of these patients.

Pathology of follicular lymphoma

Follicular lymphoma (FL) is a heterogeneous disease, and there are many different subgroups, such as in terms of age of onset, involved organ (especially extranodal sites such as gastrointestinal tract) and genetic abnormality. Grade 3B is currently regarded as a distinct entity by molecular genetic analyses, but the independence of Grade 3A remains unclear. Variations of clinical course are known in FL. Some cases are very indolent, but others are not. The latter cases show histological transformation to diffuse large B-cell lymphoma (DLBCL) (high-grade transformation) and an aggressive course. Histological transformation to DLBCL is reported to occur in about 30-40% of patients, at a rate of about 3% each year. However, it reaches a plateau at about 16 years, so the stratification of patients in whom transformation would or would not occur is very important for the therapeutic strategy. From genome-wide analysis by next-generation sequencing, EZH2, CREBBP and MLL2, which are histone-modifying genes, have been shown to be frequently mutated in FL and to have an important role in lymphomagenesis. IGH-BCL2 translocation and CREBBP mutations are early events, whereas MLL2 and TNFSFR14 mutations represent late events during disease evolution. In the 2008 WHO classification, three new variants: (1) pediatric follicular lymphoma, (2) primary intestinal follicular lymphoma and (3) in situ follicular lymphoma, are included. Pathologists and clinicians should consider these new developments when deciding on the diagnostic and therapeutic strategy.

Immunoglobulin expressions are only associated with MCPyV-positive Merkel cell carcinomas but not with MCPyV-negative ones: comparison of prognosis

Merkel cell carcinoma (MCC) is an aggressive neuroendocrine skin cancer, often associated with Merkel cell polyomavirus (MCPyV). Recently, immunoglobulin (Ig) expression was reported in MCC, thereby suggesting that B cells might be their cellular ancestors. We tested 30 MCCs (20 MCPyV-positive and 10 MCPyV-negative) using immunohistochemistry for the expressions of IgG, IgA, IgM, Igκ, Igλ, terminal desoxynucleotidyl transferase, paired box gene 5 (PAX5), octamer transcription factor-2 (Oct-2), and sex-determining region Y-box 11 (SOX11). We performed in situ hybridization for Igκ-mRNA or Igλ-mRNA and Ig heavy chain (IgH) gene rearrangement (IgH-R) analyses. The expressions of PAX5, TdT, Oct-2, and SOX11 were not significantly different between MCPyV-positive and MCPyV-negative MCCs. At least 1 of IgG, IgA, IgM, or Igκ was expressed in MCPyV-positive (14/20, 70%) and none in MCPyV-negative MCCs (P=0.0003). There was a higher tendency for Igκ-mRNA expression (7/19, using in situ hybridization) and IgH-R (10/20, using polymerase chain reaction) in MCPyV-positive than in MCPyV-negative MCCs (0/10 and 2/10, respectively), thus suggesting a different Ig production pattern and pathogenesis between the 2 types of MCC. Ig expression or IgH-R in MCPyV-positive MCCs might be associated with MCPyV gene integration or expression in cancer cells but do not necessarily suggest a B-cell origin for MCCs. IgH expression or IgH-R nonsignificantly correlated with improved prognosis. However, these might be important factors that influence the survival of neoplastic cells and might allow the development of novel therapies for patients with MCPyV-positive MCCs.

Nature and importance of follicular lymphoma precursors

It is now widely recognized that cancer development is a protracted process requiring the stepwise acquisition of multiple oncogenic events. In humans, this process can take decades, if not a lifetime, blurring the notion of 'healthy' individuals. Follicular lymphoma exemplifies this multistep pathway of oncogenesis. In recent years, variants of follicular lymphoma have been recognized that appear to represent clonal B-cell expansions at an early stage of follicular lymphoma lymphomagenesis. These include follicular lymphoma in situ, duodenal follicular lymphoma, partial involvement by follicular lymphoma, and in the blood circulating follicular lymphoma-like B cells. Recent genetic studies have identified similarities and differences between the early lesions and overt follicular lymphoma, providing important information for understanding their biological evolution. The data indicate that there is already genomic instability at these early stages, even in instances with a low risk for clinical progression. The overexpression of BCL2 in t(14;18)-positive B cells puts them at risk for subsequent genetic aberrations when they re-enter the germinal center and are exposed to the influences of activation-induced cytidine deaminase and somatic hypermutations. The emerging data provide a rationale for clinical management and, in the future, may identify genetic risk factors that warrant early therapeutic intervention.

Duodenal follicular lymphoma: comprehensive gene expression analysis with insights into pathogenesis

Follicular lymphoma (FL) of the gastrointestinal tract, particularly duodenal follicular lymphoma (DFL), is a rare variant of FL with indolent clinical behavior, and this disease is included in the 2008 World Health Organization classification system. In contrast to nodal follicular lymphoma (NFL), DFL occurs most frequently in the second part of the duodenum, lacks follicular dendritic cell meshworks and has memory B-cell characteristics. However, its molecular pathogenesis is still unclear. In the present study, we examined 10 DFL, 18 NFL and 10 gastric MALT lymphoma samples using gene expression analysis. Quantitative RT-PCR experiments and immunohistochemical analysis for 72 formalin-fixed, paraffin-embedded tissues from an independent series, including 32 DFL, 19 gastric MALT lymphoma and 27 NFL samples, were performed for validation of microarray data. Gene expression profiles of the three lymphoma types were compared using 2918 differentially expressed genes (DEG) and results suggested that DFL shares characteristics of MALT lymphoma. Among these DEG, CCL20 and MAdCAM-1 were upregulated in DFL and MALT but downregulated in NFL. In contrast, protocadherin gamma subfamily genes were upregulated in DFL and NFL. Quantitative RT-PCR and immunohistochemical studies demonstrated concordant results. Double immunofluorescence studies revealed that CCL20 and CCR6 were co-expressed in both DFL and MALT. We hypothesize that increased expression of CCL20 and MAdCAM-1 and co-expression of CCL20 and CCR6 may play an important role in tumorigenesis.

Diagnostic accuracy of endoscopic biopsies for the diagnosis of gastrointestinal follicular lymphoma: a clinicopathologic study of 48 patients

The purpose of this study was to reveal the diagnostic accuracy of initial pathologic assessment of biopsied samples in patients with gastrointestinal follicular lymphoma lesions. A total of 48 patients with follicular lymphoma (Lugano system stage I: n = 30; II1: n = 4; II2: n = 4; IV: n = 10) with gastrointestinal involvement who underwent endoscopic biopsy were enrolled and retrospectively reviewed. Nine (18.8%) of the 48 patients were not appropriately diagnosed as having follicular lymphoma at the initial biopsy. The initial pathological diagnosis included extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (n = 4), necrotic tissue (n = 2), duodenitis (n = 1), or suspected lymphoma of unspecified subtype (n = 2). The reasons for these inappropriate diagnoses were insufficient histopathologic analysis lacking CD10 and BCL2 staining (n = 7) and unsuitable biopsy samples taken from erosions or ulcers that contained scanty lymphoma cells or no lymphoid follicles (n = 2). In conclusion, incomplete histopathologic analysis and unsuitable biopsy samples are pitfalls in the diagnosis of gastrointestinal follicular lymphoma.

Elevated soluble IL-2 receptor levels correlate with tumor bulk of follicular lymphomas with intestinal involvement

OBJECTIVES

Establish a correlation between serum soluble interleukin 2 receptor (sIL-2R) levels and clinical characteristics of follicular lymphoma patients with gastrointestinal involvement.

DESIGN AND METHODS

Patients (n=44) presenting with follicular lymphoma lesions in the gastrointestinal tract were enrolled into the study and divided into 2 groups based on sIL-2R levels (normal vs. elevated). Clinical characteristics were also analyzed between groups.

RESULTS

Patients with elevated sIL-2R levels likely had systemic follicular lymphoma involvement (Ann Arbor system staging IIIES/IV or Lugano system staging II-2/IV), involvement of 5 or more nodal areas, and presentation of bulky tumors in the gastrointestinal tract. These patients also presented a high Follicular Lymphoma International Prognostic Index (FLIPI) score, suggestive of poor prognosis. No differences were found among other clinical characteristics including sex, age at lymphoma diagnosis, histological grade, LDH levels, bone marrow involvement, hemoglobin levels, and identification of tracer accumulation in gastrointestinal lesions by positron-emission tomography scanning.

CONCLUSIONS

sIL-2R levels can be used as an independent prognostic index in follicular lymphoma patients based on the correlation with the FLIPI score. Moreover, since high sIL-2R levels were associated with a large tumor bulk, sIL-2R may serve as a good indicator for monitoring disease relapse or progression.

Early lesions of follicular lymphoma: a genetic perspective

The pathogenesis of follicular lymphoma is a multi-hit process progressing over many years through the accumulation of numerous genetic alterations. Besides the hallmark t(14;18), it is still unclear which other oncogenic hits contribute to the early steps of transformation and in which precursor stages these occur. To address this issue, we performed high-resolution comparative genomic hybridization microarrays on laser-capture micro-dissected cases of follicular lymphoma in situ (n=4), partial involvement by follicular lymphoma (n=4), and duodenal follicular lymphoma (n=4), assumed to represent, potentially, the earliest stages in the evolution of follicular lymphoma. Cases of reactive follicular hyperplasia (n=2), uninvolved areas from follicular lymphoma in situ lymph nodes, follicular lymphoma grade 1-2 (n=5) and follicular lymphoma grade 3A (n=5) were used as controls. Surprisingly, alterations involving several relevant (onco)genes were found in all entities, but at significantly lower proportions than in overt follicular lymphoma. While the number of alterations clearly assigns all these entities as precursors, the pattern of partial involvement by follicular lymphoma alterations was quantitatively and qualitatively closer to that of follicular lymphoma, indicating significant selective pressure in line with its faster rate of progression. Among the most notable alterations, we observed and validated deletions of 1p36 and gains of the 7p and 12q chromosomes and related oncogenes, which include some of the most recurrent oncogenic alterations in overt follicular lymphoma (TNFRSF14, EZH2, MLL2). By further delineating distinctive and hierarchical molecular and genetic features of early follicular lymphoma entities, our analysis underlines the importance of applying appropriate criteria for the differential diagnosis. It also provides a first set of candidates likely to be involved in the cascade of hits that pave the path of the various progression phases to follicular lymphoma development.

Synchronous adenocarcinoma and follicular lymphoma of the stomach

A 73-year-old Japanese man with synchronous follicular lymphoma and adenocarcinoma of the stomach underwent curative surgical resection. The follicular lymphoma lesion was preoperatively diagnosed as extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) according to biopsy samples. However, postoperative pathological evaluations revealed components of CD10-positive and CD10-negative lymphoma cells within the lymphoma lesion. This case highlights the potential difficulty of diagnosing gastric follicular lymphoma. In such cases, conducting repeat pathological examinations of biopsy samples or resected specimens is required to obtain a correct diagnosis of follicular lymphoma.