Primary follicular lymphoma of the duodenum is a distinct mucosal/submucosal variant of follicular lymphoma: a retrospective study of 63 cases

Recent updates on treatment options for primary follicular lymphoma of the gastrointestinal tract

BACKGROUND

Primary gastrointestinal follicular lymphoma is a subtype of follicular lymphoma that originates directly from the gastrointestinal tract. Pathologically, it exhibits substantial similarities with the secondary gastrointestinal involvement observed in nodal follicular lymphoma. However, primary gastrointestinal follicular lymphoma presents clinically distinct features, necessitating divergent considerations in treatment selection compared with nodal follicular lymphoma.

AREAS COVERED

This narrative review focused on recent articles (2018-2023) regarding the long-term prognosis and treatment options for gastrointestinal follicular lymphoma. In addition, a brief overview of gastrointestinal follicular lymphomas is provided.

EXPERT OPINION

Patients with primary gastrointestinal follicular lymphoma often present with a low tumor burden. Lymphoma lesions typically remain asymptomatic for several years or may undergo spontaneous regression without immediate treatment. Therefore, a 'watch and wait' approach is justified. Conversely, when large tumor masses are identified in the gastrointestinal tract, the potential for tumor bleeding or intestinal obstruction requires timely therapeutic interventions.

Epidemiological features and prognosis for primary gastrointestinal follicular lymphoma

Primary gastrointestinal follicular lymphoma (PGI-FL) is a rare extra-nodal lymphoma. Its epidemiology and prognosis remain unclear. We performed a retrospective analysis of eligible patients with 1648 PGI-FL and 34 892 nodal FL (N-FL) in the Surveillance, Epidemiology and End Results (SEER) database. The age-adjusted average annual incidence of PGI-FL was 0.111/100000. The median overall survival (OS) for PGI-FL and N-FL patients was 207 and 165 months respectively. The 5-year diffuse large B-cell lymphoma (DLBCL) transformation rates were 2.1% and 2.6% respectively. Age, sex, grade, Ann Arbor stage, primary site and radiation were independent prognostic factors (p < 0.05). Nomograms were constructed to predict 1-, 5- and 10-year OS and disease-specific survival (DSS). The receiver operating characteristic curves and calibration plots showed the established nomograms had robust and accurate performance. Patients were classified into three risk groups according to nomogram score. In conclusion, the incidence of PGI-FL has increased over the past 40 years, and PGI-FL has a better prognosis and a lower DLBCL transformation rate than N-FL. The nomograms were developed and validated as an individualized tool to predict survival. Patients were divided into three risk groups to assist clinicians in identifying high-risk patients and choosing the optimal individualized treatments.

Comparison of Comorbidity Models Within a Population-Based Cohort of Older Adults With Non-Hodgkin Lymphoma

PURPOSE

Compare the association of individual comorbidities, comorbidity indices, and survival in older adults with non-Hodgkin lymphoma (NHL), including in specific NHL subtypes.

METHODS

Data source was SEER-Medicare, a population-based registry of adults age 65 years and older with cancer. We included all incident cases of NHL diagnosed during 2008-2017 who met study inclusion criteria. Comorbidities were classified using the three-factor risk estimate scale (TRES), Charlson comorbidity index (CCI), and National Cancer Institute (NCI) comorbidity index categories and weights. Overall survival (OS) and lymphoma-specific survival, with death from other causes treated as a competing risk, were estimated using the Kaplan-Meier method from time of diagnosis. Multivariable Cox models were constructed, and Harrel C-statistics were used to compare comorbidity models. A two-sided P value of <.05 was considered significant.

RESULTS

A total of 40,486 patients with newly diagnosed NHL were included. Patients with aggressive NHL had higher rates of baseline comorbidity. Despite differences in baseline comorbidity between NHL subtypes, cardiovascular, pulmonary, diabetes, and renal comorbidities were frequent and consistently associated with OS in most NHL subtypes. These categories were used to construct a candidate comorbidity score, the non-Hodgkin lymphoma 5 (NHL-5). Comparing three validated comorbidity scores, TRES, CCI, NCI, and the novel NHL-5 score, we found similar associations with OS and lymphoma-specific survival, which was confirmed in sensitivity analyses by NHL subtypes.

CONCLUSION

The optimal measure of comorbidity in NHL is unknown. Here, we demonstrate that the three-category TRES and five-category NHL-5 scores perform as well as the 14-16 category CCI and NCI scores in terms of association with OS and lymphoma-specific survival. These simple scores could be more easily used in clinical practice without prognostic loss.

In Situ Follicular B-Cell Neoplasm Presenting as Miliary Facial Papules: A Unique Clinical Presentation and Spontaneous Regression

ABSTRACT

In situ follicular B-cell neoplasm (ISFN) is a variant of follicular lymphoma, presenting as an incidental histologic finding in lymph node biopsy or excisional specimens. ISFN presents with a B-cell population that strongly expresses BCL2 and CD10 within the germinal centers of a lymph node or extranodal site. Genetic analysis shows t(14;18) translocation. Herein, we report a case of ISFN presenting as military and agminated facial papules in a young woman, which resolved spontaneously in the postpartum period. To our knowledge, this is the only report of a cutaneous site of involvement of this rare entity.

Clinicopathological characteristics of duodenal-type follicular lymphoma: A case report

BACKGROUND

Duodenal-type follicular lymphoma (D-FL) is very rare in clinical practice. Since its clinical manifestations are similar to those of intestinal inflammation or polyps, D-FL is prone to misdiagnosis or missed diagnosis.

CASE SUMMARY

Inexperienced clinical physicians are prone to misdiagnosing D-FL as polyps or inflammation, and it should be distin-guished from intense follicular hyperplasia and lymphoma with follicular structure. Immunohistochemistry (IHC) and molecular techniques are required for its clear diagnosis.

CONCLUSION

D-FL mainly occurs in the descending part of the duodenum, but it can also affect the distal small intestine. Endoscopically, the mucosa shows polyp-like proliferation. IHC staining shows that the tumor cells are positive for CD20, CD79α, CD10, Bcl-6, and Bcl-2, and CD21 labeled follcular dendritic cells show a characteristic "duodenal pattern". BCL2/t(14;18) fusion is often present. D-FL has a good prognosis, and its prognosis needs follow-up observation.

[Studies on clinicopathological features of duodenal-type follicular lymphoma of 18 patients]

To investigate the clinical and pathological characteristics of duodenal-type follicular lymphoma (D-FL), and to deepen the understanding of Duodenal-type follicular lymphoma. The clinical symptoms, endoscopic features, pathologic features, immunophenotype, molecular pathological features and treatment follow-up of 18 D-FL patients diagnosed in Department of Pathology, Beijing Tiantan Hospital affiliated to Capital Medical University between January 2020 and July 2023 were summarized. A total of 18 patients with D-FL were included, including 10 males and 8 females. The median age was 49 (32-69) years respectively. Most of the patients were found during gastroenteroscopy or presented with the common gastrointestinal symptoms of stomach pain, acid reflux, vomiting and diarrhea. Most endoscopic findings were multiple small gray and white polyposis. In the pathological morphology, the mucous layer and submucous layer showed lymphoid follicular structures with full and strained follicles. The immunophenotype showed that the tumor cells strongly expressed CD20 and BCL2 and had low proliferation activity. Immunoglobulin clonal analysis of 1 case showed IgK monoclonal rearrangement (1/1). FISH showed 1 case of BCL2 gene rearrangement (1/3). All patients did not receive targeted chemotherapy and adopted a wait-and-see strategy. Median follow-up was 12 (2-34) months. This study shows that D-FL is an indolent lymphoma, which tends to occur in the duodenum and has a good prognosis.

Gene targeted and immune therapies for nodal and gastrointestinal follicular lymphomas

Follicular lymphoma (FL) is the most common indolent B-cell lymphoma (BCL) globally. Recently, its incidence has increased in Europe, the United States, and Asia, with the number of gastrointestinal FL cases expected to increase. Genetic abnormalities related to t(14;18) translocation, BCL2 overexpression, NF-κB pathway-related factors, histone acetylases, and histone methyltransferases cause FL and enhance its proliferation. Meanwhile, microRNAs are commonly used in diagnosing FL and predicting patient prognosis. Many clinical trials on novel therapeutics targeting these genetic abnormalities and immunomodulatory mechanisms have been conducted, resulting in a marked improvement in therapeutic outcomes for FL. Although developing these innovative therapeutic agents targeting specific genetic mutations and immune pathways has provided hope for curative options, FL treatment has become more complex, requiring combinatorial therapeutic regimens. However, optimal treatment combinations have not yet been achieved, highlighting the importance of a complete under-standing regarding the pathogenesis of gastrointestinal FL. Accordingly, this article reviews key research on the molecular pathogenesis of nodal FL and novel therapies targeting the causative genetic mutations. Moreover, the results of clinical trials are summarized, with a particular focus on treating nodal and gastrointestinal FLs.

Disease surveillance evaluation of primary small-bowel follicular lymphoma using capsule endoscopy images based on a deep convolutional neural network (with video)

BACKGROUND AND AIMS

Capsule endoscopy (CE) is useful in evaluating disease surveillance for primary small-bowel follicular lymphoma (FL), but some cases are difficult to evaluate objectively. This study evaluated the usefulness of a deep convolutional neural network (CNN) system using CE images for disease surveillance of primary small-bowel FL.

METHODS

We enrolled 26 consecutive patients with primary small-bowel FL diagnosed between January 2011 and January 2021 who underwent CE before and after a watch-and-wait strategy or chemotherapy. Disease surveillance by the CNN system was evaluated by the percentage of FL-detected images among all CE images of the small-bowel mucosa.

RESULTS

Eighteen cases (69%) were managed with a watch-and-wait approach, and 8 cases (31%) were treated with chemotherapy. Among the 18 cases managed with the watch-and-wait approach, the outcome of lesion evaluation by the CNN system was almost the same in 13 cases (72%), aggravation in 4 (22%), and improvement in 1 (6%). Among the 8 cases treated with chemotherapy, the outcome of lesion evaluation by the CNN system was improvement in 5 cases (63%), almost the same in 2 (25%), and aggravation in 1 (12%). The physician and CNN system reported similar results regarding disease surveillance evaluation in 23 of 26 cases (88%), whereas a discrepancy between the 2 was found in the remaining 3 cases (12%), attributed to poor small-bowel cleansing level.

CONCLUSIONS

Disease surveillance evaluation of primary small-bowel FL using CE images by the developed CNN system was useful under the condition of excellent small-bowel cleansing level.

Biliary obstruction secondary to duodenal follicular lymphoma with papillary involvement

Duodenal-type follicular lymphoma is a clinical variant of follicular lymphoma located in the intestine, presenting as multiple small polyps. The estimated frequency is 1/7000 people and extraduodenal involvement is rare. It predominantly affects middle-aged women, although some cases of young patients have been published in the literature. They are usually located in the second periampullary portion of the duodenum. It is diagnosed incidentally or after performing an imaging test due to non-specific digestive symptoms (abdominalgia, diarrhea or hyporexia). The prognosis is usually favorable without specific treatment5.

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.

Recent advances in treatment of nodal and gastrointestinal follicular lymphoma

Follicular lymphoma (FL) is the most common low-grade lymphoma, and although nodal FL is highly responsive to treatment, the majority of patients relapse repeatedly, and the disease has been incurable with a poor prognosis. However, primary FL of the gastrointestinal tract has been increasingly detected in Japan, especially due to recent advances in small bowel endoscopy and increased opportunities for endoscopic examinations and endoscopic diagnosis. However, many cases are detected at an early stage, and the prognosis is good in many cases. In contrast, in Europe and the United States, gastrointestinal FL has long been considered to be present in 12%-24% of Stage-IV patients, and the number of advanced gastrointestinal cases is expected to increase. This editorial provides an overview of the recent therapeutic advances in nodal FL, including antibody-targeted therapy, bispecific antibody therapy, epigenetic modulation, and chimeric antigen receptor T-cell therapy, and reviews the latest therapeutic manuscripts published in the past year. Based on an understanding of the therapeutic advances in nodal FL, we also discuss future possibilities for gastroenterologists to treat gastrointestinal FL, especially in advanced cases.

Navigating the Heterogeneity of Follicular Lymphoma and its Many Variants: An Updated Approach to Diagnosis and Classification

Follicular lymphoma (FL) is a lymphoid neoplasm composed of follicle center (germinal center) B cells, with varying proportions of centrocytes and centroblasts, that usually has a predominantly follicular architectural pattern. Over the past decade, our understanding of FL has evolved significantly, with new recognition of several recently defined FL variants characterized by distinct clinical presentations, behaviors, genetic alterations, and biology. This manuscript aims to review the heterogeneity of FL and its variants, to provide an updated guide on their diagnosis and classification, and to describe how approaches to the histologic subclassification of classic FL have evolved in current classification schemes.

Long-term outcomes of patients with primary intestinal follicular lymphoma managed with watch-and-wait strategy

Patients with primary intestinal follicular lymphoma are often followed-up without a specific treatment, and this approach is called the "watch-and-wait approach." However, the long-term outcomes of this patient group have not been sufficiently investigated. We enrolled patients with primary intestinal follicular lymphoma who were diagnosed before 2016 and managed with the watch-and-wait approach in 20 institutions. We retrospectively investigated the overall, disease-specific, and event-free survival rates as well as the rate of spontaneous regression. Among the 248 patients with follicular lymphoma with gastrointestinal involvement, 124 had localized disease (stage I or II₁). We analyzed the data of 73 patients who were managed using the watch-and-wait approach. During the mean follow-up period of 8.3 years, the follicular lymphoma had spontaneously resolved in 16.4% of the patients. The 5-year and 10-year overall survival rates were 92.9% and 87.1%, respectively. With disease progression (n = 7), initiation of therapy (n = 7), and histologic transformation to aggressive lymphoma (n = 0) defined as events, the 5-year and 10-year event-free survival rates were 91.1% and 86.9%, respectively. No patient died of progressive lymphoma. Thus, both 5-year and 10-year disease-specific survival rates were 100%. In conclusion, an indolent long-term clinical course was confirmed in the patients with primary intestinal follicular lymphoma. The watch-and-wait strategy is a reasonable approach for the initial management of these patients.

Clinicopathological and molecular genetic characteristics of primary gastric follicular lymphoma☆,☆☆,☆☆☆

Primary gastric follicular lymphomas (FLs) have been rarely reported and little is known about their characteristics. In the present study, we report five cases of primary gastric FL and describe their clinicopathological and molecular genetic features. A total of seven samples from five patients were investigated for clinicopathological characteristics and somatic mutations by the targeted sequencing of 50 lymphoma-related genes. Two cases were identified as slightly elevated submucosal tumors and three cases as polypoid tumors. Histologically, all cases were low-grade FLs. The immuno-profile was CD20⁺/CD10⁺/BCL2⁺ in four cases and CD20⁺/CD10⁺/BCL2^- in one case. Immunostaining pattern for CD21 was similar to that of classic FL. BCL2 rearrangement was not identified in fluorescence in situ hybridization studies in any of the five cases. NGS analysis showed mutations in genes involved in epigenetic modifications (KMT2D, ARID1A, EP300, CREBBP), NK-kB pathway (CARD11), and JAK-STAT pathway as found in classic follicular lymphoma. All cases presented with clinical I without the involvement of regional or systemic lymph nodes. Four patients were well, whereas one patient who received endoscopic mucosal resection of tumor without additional chemotherapy or radiotherapy experienced three relapses. In conclusion, primary gastric FL is characterized by a low-grade neoplasm with infrequent BCL2 rearrangement. After resection of the lesion, additional treatment such as radiation therapy or chemotherapy is required as there is a possibility of recurrence.

Review of lymphoma in the duodenum: An update of diagnosis and management

The presentation, subtype, and macroscopic images of lymphoma vary depending on the site of the tumor within the gastrointestinal tract. We searched PubMed for publications between January 1, 2012 and October 10, 2022, and retrieved 130 articles relating to duodenal lymphoma. A further 22 articles were added based on the manual screening of relevant articles, yielding 152 articles for full-text review. The most predominant primary duodenal lymphoma was follicular lymphoma. In this review, we provide an update of the diagnosis and man-agement of representative lymphoma subtypes occurring in the duodenum: Follicular lymphoma, diffuse large B-cell lymphoma, extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue, mantle cell lymphoma, and T-cell lymphomas.

Follicular lymphoma: an update on biology and optimal therapy

Follicular lymphoma (FL) is a mature B-cell neoplasm with a mostly indolent course. Genetic hallmark characteristics are Bcl-2 overexpression based on a t(14;18) translocation and additional secondary genetic and epigenetic aberrations. Standard treatment for early-stage patients has curative intent and usually consists of radiotherapy with or without rituximab. In the advanced stage, the main therapeutic focus is on prolonged remissions. Therefore, treatment in asymptomatic patients is usually deferred. Symptomatic patients are subject to immunochemotherapy induction followed by antibody maintenance. Importantly, about one in five patients subsequently experiences a more rapid clinical course, achieving only short remissions with multiple relapses (POD24). In those patients, there is still an urgent need for improved therapeutic options. Accordingly, a plethora of targeted and immunotherapeutic options, including immunomodulatory drugs, small molecule inhibitors, monoclonal antibodies as well as bispecific T-cell engager antibodies and CAR-T cell products have been recently evaluated in such relapsed high-risk patients.

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.

Follicular lymphoma: 2023 update on diagnosis and management

DISEASE OVERVIEW

Follicular lymphoma (FL) is generally an indolent B cell lymphoproliferative disorder of transformed follicular center B cells. FL is characterized by diffuse lymphadenopathy, bone marrow involvement, and splenomegaly. Extranodal involvement is less common. Cytopenias are relatively common but constitutional symptoms of fever, night sweats, and weight loss are uncommon in the absence of transformation to diffuse large B cell lymphoma.

DIAGNOSIS

The diagnosis is based on histology from a biopsy of a lymph node or other affected tissue. Incisional biopsy is preferred over needle biopsies in order to give adequate tissue to assign grade and assess for transformation. Immunohistochemical staining is positive in virtually all cases for cell surface CD19, CD20, CD10, and monoclonal immunoglobulin, as well as cytoplasmic expression of bcl-2 protein. The overwhelming majority of cases have the characteristic t(14;18) translocation involving the IgH/bcl-2 genes.

RISK STRATIFICATION

The Follicular Lymphoma International Prognostic Index (FLIPI) uses five independent predictors of inferior survival: age >60 years, hemoglobin <12 g/dL, serum LDH > normal, Ann Arbor stage III/IV, number of involved nodal areas >4. The presence of 0-1, 2, and ≥3 adverse factors defines low, intermediate, and high-risk disease. There are other clinical prognostic models but the FLIPI remains the most common. Other factors such as time to relapse of less than 2 years from chemoimmunotherapy and specific gene mutations may also be useful for prognosis. Regardless of the prognostic model used, modern therapies have demonstrably improved prognosis.

RISK-ADAPTED THERAPY

Observation continues to be appropriate for asymptomatic patients with low bulk disease and no cytopenias. There is no overall survival (OS) advantage for early treatment with either chemotherapy or single-agent rituximab. For patients needing therapy, most patients are treated with chemoimmunotherapy, which has improved overall response rates (ORR), DOR, and OS. Randomized studies have shown additional benefits for maintenance of rituximab. Lenalidomide was non-inferior to chemoimmunotherapy in a randomized front-line study and, when combined with rituximab, was superior to rituximab alone in relapsed FL. Kinase inhibitors, stem cell transplantation (SCT), and chimeric antigen receptor T cells (CAR-T) are also considered for recurrent disease.

Predictive factors for the progression of primary localized stage small-bowel follicular lymphoma

BACKGROUND

Primary small-bowel follicular lymphoma (FL) is mainly diagnosed as a duodenal lesion during esophagogastroduodenoscopy. Recently, with the widespread use of small-bowel endoscopy, FL in the jejunum and ileum has been detected. Most patients with small-bowel FL are diagnosed at the localized stage, and a watch-and-wait policy is used. However, the predictive factors for the progression of small-bowel FL have not been clarified. This study retrospectively examined the predictive factors for the progression of primary localized stage small-bowel FL based on clinicopathological and endoscopic findings.

METHODS

We enrolled 60 consecutive patients with primary small-bowel FL diagnosed at two tertiary hospitals between January 2005 and December 2020, with localized stage, low grade, and low tumor burden with the watch-and-wait policy. We examined the predictive factors for progression according to the clinicopathological and endoscopic findings. Endoscopic findings were focused on the color tone, circumferential location of follicular lesions (circumference ≥ 1/2 or < 1/2), fusion of follicular lesions (fusion [ +] or [ -]), and protruded lesions (≥ 6 mm or < 6 mm).

RESULTS

Progressive disease was observed in 12 (20%) patients (mean observation period, 76.4 ± 55.4 months). In the multivariate analysis, "circumference ≥ 1/2" and "fusion (+)" were significant predictive factors for progression. According to the Kaplan-Meier analysis, progression-free survival was significantly shorter in the "circumference ≥ 1/2" and/or "fusion (+)" group than in the "circumference < 1/2" and "fusion ( -)" group.

CONCLUSIONS

Endoscopic findings of "circumference ≥ 1/2" and "fusion (+)" were significant predictive factors for the progression of primary localized stage small-bowel FL.

Duodenal-type follicular lymphoma more than 10 years after treatment intervention: A retrospective single-center analysis

BACKGROUND

Duodenal-type follicular lymphoma (D-FL) has been recognized as a rare entity that accounts for approximately 4% of primary gastrointestinal lymphomas. D-FL follows an indolent clinical course compared with common nodal FL and is generally considered to have a better prognosis. Therefore, the “watch and wait” approach is frequently adopted as the treatment method. Alternatively, there is an option to actively intervene in D-FL. However, the long-term outcomes of such cases are poorly understood.

AIM

To clarify the clinical outcomes after long-term follow-up in cases of D-FL with treatment intervention.

METHODS

We retrospectively analyzed patients who met the following criteria: the lesion was confirmed by endoscopy, the diagnosis of D-FL was confirmed histopathologically, and the patient was followed-up for more than 10 years after the intervention at our center.

RESULTS

We identified 5 cases of D-FL. Two patients showed a small amount of bone marrow involvement (Stage IV). Rituximab was used as a treatment for remission in all 5 patients. It was also used in combination with chemotherapy in 2 Stage IV patients as well as for maintenance treatment. Radiation therapy was performed in 2 cases, which was followed by complete remission (CR). Eventually, all 5 patients achieved CR and survived for more than 10 years. However, 3 patients experienced recurrence. One patient achieved a second CR by retreatment, and in another case, the lesion showed spontaneous disappearance. The remaining patient had systemic widespread recurrence 13 years after the first CR. Biopsy results suggested that the FL lesions were transformed into diffuse large B-cell lymphoma. The patient died 4 years later despite receiving various chemotherapies.

CONCLUSION

In this study, the treatment for patients of D-FL in Stage IV was successful. In the future, criteria for how to treat “advanced” D-FL should be established based on additional cases. This study of patients with D-FL indicates that whole-body follow-up examinations should continue for a long time due to a fatal recurrence 13 years after reaching CR.

Efficacy and Safety of Exploring Deeper Sections of the Infrapapillary Area of the Duodenum by Using Sedative Esophagogastroduodenoscopy

Background

Using conventional esophagogastroduodenoscopy (EGD) to evaluate the infrapapillary area is not feasible. The use of sedative EGD may enable endoscopists to investigate the infrapapillary condition of the duodenum. In this study, we aimed to evaluate lesions in the infrapapillary regions by using sedative EGD.

Methods

In this retrospective observational study, we used the data of patients who underwent sedative EGD examinations at a tertiary hospital in southern Taiwan. The endoscopists evaluated the esophagus, stomach, and proximal duodenum and then attempted to explore the infrapapillary portion of the duodenum as deeply as possible. We assessed the success rate for the exploration of infrapapillary areas. Furthermore, we analyzed specific clinical findings of sedative EGD examination.

Results

In total, 2973 patients underwent sedative EGD between November 1, 2010, and December 31, 2011. For 2632 of these patients, it was their first sedative EGD examination. In 2511 patients (95.4%), the exploration of the infrapapillary areas was successful. In approximately 10% of the patients, specific findings were detected over the infrapapillary region, and 7 of these patients exhibited clinically significant findings (i.e., gallbladder cancer with metastasis, periampullary Vater adenoma, natural killer cell enteropathy, villous adenoma with moderate dysplasia, infrapapillary duodenal adenoma with dysplasia, duodenal perforation with tumor-like formation, and follicular lymphoma). No patient experienced minor or major adverse reactions during the sedative EGD procedure.

Conclusions

The current study provided evidence that sedative EGD examination enables a safe, comfortable, and effective endoscopic examination of deeper sections of the duodenum to evaluate the papillary and infrapapillary regions.

Protein-losing Enteropathy Complicated with Primary Intestinal Follicular Lymphoma

Protein-losing enteropathy (PLE) is a rare syndrome characterized by hypoproteinemia due to gastrointestinal (GI) protein loss. Primary intestinal follicular lymphoma (PIFL), a specific variant of follicular lymphoma with essential only GI involvement, has not been reported as an etiology of PLE. We herein report a case of PLE complicated with PIFL that was successfully treated with rituximab, resulting in rapid improvement of PLE and a complete response of PIFL. Macroscopic findings of ulcerative lesions with diffuse involvement, which were precisely described by capsule and double-balloon enteroscopy at the diagnosis, also improved following the treatment. This case provides a clue suggesting factors that promote PLE in PIFL.

Clinical features and outcomes of duodenal‐type follicular lymphoma: A single‐center retrospective study

Duodenal‐type follicular lymphoma (FL) is a rare and newly recognized disease. Few data are available on the outcomes and treatment strategies for patients with duodenal‐type FL. We aimed to investigate the clinical features and outcomes of duodenal‐type FL. We defined duodenal‐type FL as involvement of the duodenum, without nodal or extranodal lesions other than intestinal lesions, pathologically diagnosed as FL. We reviewed 26 patients with duodenal‐type FL between January 2011 and December 2020 at Kobe City Hospital Organization, Kobe City Medical Center General Hospital. In particular, patients were selected for the watch and wait (WW) strategy and followed up with regular esophagogastroduodenoscopy about once a year at our institution. The patient characteristics were as follows: median age 63.5 years (range: 42–78), sex (male, 15; female, 11), stage (I, 26), and grade (I, 26). Regarding treatment strategies, 23 patients were selected for the WW strategy, and three patients received initial rituximab therapy. The median follow‐up period was 65.5 months (range: 0.2–109). Five‐year progression‐free survival and 5‐year overall survival rates were 86.3% and 100%, respectively. Among the 23 patients selected for the WW strategy, six had spontaneous complete regression, and 14 had stable disease, and three had progressive disease, including one with histologic transformation. The WW strategy for patients with duodenal‐type FL could be an appropriate and safe treatment option. However, in several cases, disease progression was documented, and regular follow‐up is important.

Duodenal Follicular Lymphoma: Track or Treat?

Duodenal follicular lymphoma (DFL) is a rare variety of non-Hodgkin's lymphoma of the gastrointestinal tract that usually carries a favorable course, recognized as a new entity in 2016. It is usually diagnosed at an early stage located predominantly in the second portion of the duodenum. We report the case of a 74-year-old male patient with epigastric pain in whom gastroscopy revealed white mucosal nodules that were pathologically diagnosed as grade 1-2 DFL. Staging investigations revealed secondary lesions in the spleen and at the base of the tongue together with latero-cervical adenopathy. The tumor was stage IV according to the Lugano staging system. We reviewed the recent (last five years) literature defining the importance of combination therapy in the advanced stage. The patient achieved complete remission of the disease through chemoimmunotherapy following the Rituximab-Bendamustine scheme.

Primary Gastrointestinal Follicular Lymphomas: A Prospective Study of 31 Patients with Long-term Follow-up Registered in the French Gastrointestinal Lymphoma Study Group (GELD) of the French Federation of Digestive Oncology (FFCD)

Background/Aims

Methods

Results

Conclusions

Primary Gastrointestinal Follicular Lymphoma Presenting With Bowel Stenosis

Primary follicular lymphomas of the small bowel generally present with small whitish nodules and masses or polyp-like lesions; cases with other morphologies are extremely rare. We experienced a case of primary follicular lymphoma that presented with small bowel stenosis. The lesion needed to be differentiated from other causes, such as bowel tuberculosis, non-steroidal anti-inflammatory drug-related ulcers, Crohn’s disease, small bowel ischemia, trauma, and idiopathic bowel stenosis, but endoscopic biopsies did not result in a definite diagnosis. Therefore, the lesion was surgically resected and, consequently, a diagnosis of follicular lymphoma of the small bowel was finally made. We report the characteristics and macroscopic findings of follicular lymphoma of the small bowel along with a review of relevant literature.

A case of duodenal-type follicular lymphoma

An 83 years-old female with history of silicosis was referred for upper endoscopy for duodenal wall thickness detected in thoracic computer tomography (CT). Upper endoscopy revealed multiple small (1 to 5mm) whitish polypoid lesions, involving a discrete portion of the descending part of the duodenum with 3cm of extension.

Ibritumomab Tiuxetan Radioimmunotherapy for Primary Gastrointestinal Follicular Lymphoma

Primary gastrointestinal follicular lymphoma (PGIFL) is characterized by localized involvement of the gastrointestinal (GI) tract. PGIFL usually runs an indolent course. External beam radiation therapy is curative in a substantial proportion of localized follicular lymphomas, but GI toxicities may discourage its use in PGIFL. Ibritumomab tiuxetan radioimmunotherapy (RIT) is a radioimmunoconjugate of anti-CD20 monoclonal antibody linked to chelator tiuxetan and radioisotope. RIT delivers confined high-intensity radiation with short path length specifically targeting lymphoma cells and sparing normal tissue. In this case series report, we included six cases of PGIFL treated with RIT. All patients had low-risk, localized, and nonbulky disease. All patients responded completely and were relapse-free for the duration of follow-up. Hematologic toxicities were seen, but none were serious. RIT is a potentially curative treatment option in PGIFL with a tolerable toxicity profile.

Molecular Pathogenesis of Primary Gastrointestinal Tract Lymphomas

Primary gastrointestinal lymphomas are rare though the incidence is significantly increased among adult patients in recent years. The majority of the patients present with symptoms overlapping with other gastrointestinal disorders and imaging findings are not specific. Therefore, histologic examination is necessary to establish the diagnosis. Insight into etiologies, molecular pathogenesis and critical signaling pathways in lymphomas including gastrointestinal lymphomas has significantly expanded within the last 3 decades. Given the increasing demand for incorporation of genetic data, the appropriate handling and processing of small endoscopic gastrointestinal biopsy samples of suspected lymphoma is becoming extremely crucial and at times challenging. The use of next generation sequencing with analysis of genes relevant to diagnosis, prognosis, and therapeutic targets continues to have a significant promising impact on management of patients in lymphoid malignancies. In particular, the identification of constitutively activated pathways and the emergence of novel targeted medications predict that more effective therapies will be identified for these disorders in the coming years.

Gastrointestinal Tract Lymphomas: A Review of the Most Commonly Encountered Lymphomas

CONTEXT.—

The gastrointestinal (GI) tract is the most common site of extranodal non-Hodgkin lymphoma, accounting for 20% to 40% of all extranodal lymphomas. The majority of these are systemic processes secondarily involving the GI tract. Primary GI lymphomas are less common, accounting for approximately 10% to 15% of all non-Hodgkin lymphoma. Most non-Hodgkin lymphoma involving the GI tract are of B-cell lineage, of which diffuse large B-cell lymphoma is the most common subtype, irrespective of location.

OBJECTIVE.—

To review the lymphoproliferative neoplasms of B-cell and T-cell lineage involving the luminal GI tract according to the most prevalent subtypes at each anatomic site.

DATA SOURCE.—

Systematic search of the PubMed database for updated literature on GI lymphomas epidemiology, subtypes, clinical, endoscopic, and genetic findings. Histologic images are derived from our collection of clinical cases.

CONCLUSIONS.—

The GI tract is the most common site of extranodal lymphoproliferative neoplasms. Recognition of the most frequently encountered GI lymphomas is imperative for patient management and treatment.

Update on B-cell lymphoproliferative disorders of the gastrointestinal tract

The gastrointestinal (GI) tract is home to a significant portion of the immune system, which interacts daily with the antigenic milieu of its contents. Therefore, the presence of white blood cells within the walls of the GI tract upon histologic examination is a familiar sight on GI biopsies-both in health and disease. The GI tract is the most common site of extranodal lymphomas, most of which are B-cell neoplasms. Here, we review common and uncommon B-cell neoplasms of the GI tract - extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma), mantle cell lymphoma, duodenal-type follicular lymphoma, diffuse large B-cell lymphoma, plasmablastic lymphoma, EBV-positive mucocutaneous ulcer, and post-transplant lymphoproliferative disorders - with special focus on literature published during the past five years. Along with the other articles in this edition of Seminars in Diagnostic Pathology, it is the authors' hope that this review proves to be a useful resource in the workup of the array of hematopoietic processes that can involve the GI tract.

How we treat mature B-cell neoplasms (indolent B-cell lymphomas)

Mature B cell neoplasms, previously indolent non-Hodgkin lymphomas (iNHLs), are a heterogeneous group of malignancies sharing similar disease courses and treatment paradigms. Most patients with iNHL have an excellent prognosis, and in many, treatment can be deferred for years. However, some patients will have an accelerated course and may experience transformation into aggressive lymphomas. In this review, we focus on management concepts shared across iNHLs, as well as histology-specific strategies. We address open questions in the field, including the influence of genomics and molecular pathway alterations on treatment decisions. In addition, we review the management of uncommon clinical entities including nodular lymphocyte-predominant Hodgkin lymphoma, hairy cell leukemia, splenic lymphoma and primary lymphoma of extranodal sites. Finally, we include a perspective on novel targeted therapies, antibodies, antibody-drug conjugates, bispecific T cell engagers and chimeric antigen receptor T cell therapy.

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.

Scientific Advances and the Evolution of Diagnosis, Subclassification and Treatment of Lymphoma

The diagnosis of lymphoma has evolved tremendously over time. Initially, diagnosis of lymphoma was largely based on morphology alone. Over time, immunophenotyping using flow cytometry and immunohistochemistry, and then in situ hybridization, have contributed dramatically to the pathologist's ability to recognize, diagnose and subclassify lymphomas more precisely. In recent years, cytogenetic and molecular genetic techniques have developed that allow evaluation of abnormalities in lymphomas, leading to an understanding of their pathogenesis and opening the door to targeted therapies that will lead to better outcomes for lymphoma patients.

Primary Colorectal Follicular Lymphoma Observed by Magnifying Endoscopy, with a Five-year Follow-up

Colorectal involvement is very rare in cases of follicular lymphoma. Colonoscopy of a 69-year-old man revealed an aggregation of multiple whitish nodules in the sigmoid colon. Magnifying endoscopy with narrow-band imaging demonstrated a coiled and elongated microvascular pattern on the surface and crystal violet staining showed a type I pit pattern. A biopsy showed follicular lymphoma (Grade 1), and no other involvement of lymphoma was detected. Following a diagnosis of primary colorectal follicular lymphoma stage I (Lugano classification), the patient was monitored by watch-and-wait therapy. We documented the endoscopic images of colorectal follicular lymphoma in the present case.

Tumour-immune microenvironment in duodenal-type follicular lymphoma

Despite duodenal-type follicular lymphoma (DTFL) being morphologically, immunophenotypically and genetically indistinguishable from nodal FL (nFL), this entity typically shows a significantly better prognosis. Here, we analysed the tumour immune microenvironments of diagnostic specimens from patients with DTFL (n = 30), limited-stage FL (LSFL; n = 19) and advanced-stage FL (ASFL; n = 31). The mean number of CD8⁺ tumour-infiltrating lymphocytes (TILs) in the neoplastic follicles was higher in DTFL (1,827/mm² ) than in LSFL (1,150/mm² ) and ASFL (1,188/mm² ) (P = 0·002, P = 0·002, respectively). In addition, CD8⁺ PD1^-  T cells with non-exhausting phenotype were more abundant in the peripheral blood (PB) of DTFL than in LSFL and ASFL, indicating that DTFL may exhibit a better and longer-lasting T cell-mediated immune response. Moreover, whereas FOXP3⁺ CTLA-4⁺ effector regulatory T cells (eTregs) were rarely observed in the neoplastic follicles of DTFL (mean: 12/mm² ), they were more abundant in LSFL (78/mm² ) and ASFL (109/mm² ) (P = 2·80 × 10^-5 , P = 4·74 × 10^-8 , respectively), and the numbers of eTregs correlated inversely with those of CD8⁺ TILs (r = -0267; P = 0·018). Furthermore, DTFL showed significantly fewer circulating FOXP3^hi CD45RA^- CD25^hi eTregs (0·146%) than ASFL (0·497%) and healthy controls (0·639%) (P = 0·0003, P = 6·79 × 10^-7 , respectively). These results suggest that the augmented anti-tumour immune reactions may contribute to a better prognosis on DTFL.

Follicular lymphoma: 2020 update on diagnosis and management

DISEASE OVERVIEW

Follicular lymphoma (FL) is generally an indolent B cell lymphoproliferative disorder of transformed follicular center B cells. Follicular lymphoma is characterized by diffuse lymphadenopathy, bone marrow involvement, and splenomegaly. Extranodal involvement is less common. Cytopenias are relatively common but constitutional symptoms of fever, night sweats, and weight loss are uncommon in the absence of transformation to diffuse large B cell lymphoma.

DIAGNOSIS

The diagnosis is based on histology from a biopsy of a lymph node or other affected tissue. Incisional biopsy is preferred over needle biopsies in order to give adequate tissue to assign grade and assess for transformation. Immunohistochemical staining is positive in virtually all cases for cell surface CD19, CD20, CD10 and monoclonal immunoglobulin, as well as cytoplasmic expression of bcl-2 protein. The overwhelming majority of cases have the characteristic t(14;18) translocation involving the IgH/bcl-2 genes.

RISK STRATIFICATION

The Follicular Lymphoma International Prognostic Index (FLIPI) uses five independent predictors of inferior survival: age > 60 years, hemoglobin <12 g/dL, serum LDH > normal, Ann Arbor stage III/IV, number of involved nodal areas >4. The presence of 0-1, 2, and ≥ 3 adverse factors defines low, intermediate, and high-risk disease. There are other clinical prognostic models but the FLIPI remains the most common. Other factors such as time to relapse of less than 2 years from chemoimmunotherapy and specific gene mutations may also be useful for prognosis. Regardless of the prognostic model used, modern therapies have demonstrably improved prognosis.

RISK-ADAPTED THERAPY

Observation continues to be appropriate for asymptomatic patients with low bulk disease and no cytopenias. There is no overall survival advantage for early treatment with either chemotherapy or single agent rituximab. For patients needing therapy, most patients are treated with chemoimmunotherapy, which has improved response rates, duration of response and overall survival (OS). Randomized studies have shown additional benefit for maintenance rituximab. Lenalidomide was non-inferior to chemoimmunotherapy in a randomized front-line study and, when combined with rituximab, was superior to rituximab alone in relapsed FL. Kinase inhibitors, other immunotherapies, and stem cell transplantation (SCT) are also considered for recurrent disease.

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.

Pathology and diagnosis of follicular lymphoma and related entities

Follicular lymphoma (FL) is an indolent, mature B-cell neoplasm classically characterised by the t(14;18)(q32;q21) with constitutive overexpression of the anti-apoptotic protein, BCL2. Most cases present in older adults with slowly progressive lymphadenopathy and follow an indolent clinical course. Typical morphology shows an expansile follicular proliferation with tumour expression of germinal centre markers, and bone marrow involvement at diagnosis is frequent. However, in the recent past, efforts to understand the biological and clinical heterogeneity of FL has effected significant change to the diagnostic approach. While morphological grade, assessed by enumerating large 'centroblasts' in the neoplastic follicles, generally correlates with outcome in systemic nodal FL, variants with high-grade morphology but indolent clinical behaviour have been identified. Given the clinical implications of these FL variants, knowledge of their clinical and histopathological defining features is of paramount importance to the pathologist. Furthermore, as with many areas of diagnostic oncology, precursors to FL have been identified and described with measurable rates of progression to bona fide lymphoma. Accurate diagnosis of these early lesions can often prevent unnecessary therapy and guide appropriate monitoring for disease progression. This review aims to summarise these key pathological and diagnostic features of FL. We further highlight the biological underpinnings of FL that will likely affect the classification, diagnosis, and treatment of patients with lymphoma.

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.

[Revised WHO classification of tumors of hematopoietic and lymphoid tissues, 2017 (4th edition):lymphoid tumors]

The paper is devoted to changes in the 4^th edition of the WHO classification of lymphoid tumors in the 2017 revision, to the principles of the structure and features of the classification. It discusses changes in the identification of new clinical and morphological categories and in the abolition of some previously existing ones. New information about lymphoid tumors, their immunophenotypic and molecular characteristics of classification importance are briefly outlined. The absolute need for molecular genetic studies for the diagnosis of certain lymphoproliferative diseases is underlined. The characteristics of lymphoid pretumor states are given.

Early Events in Lymphoid Neoplasms and Indolent Follicular Lymphomas

Technical advances in diagnostic modalities have led to the characterization of indolent lymphoid disorders similar to the in situ lesions described in epithelial malignancies. These early and indolent lymphoid lesions share clinicopathologic characteristics with well-characterized lymphoid malignancies such as chronic lymphocytic leukemia and follicular lymphoma. The in situ lesions have an indolent clinical course with only a minor subset shown to progress to frank malignancies. In addition to the in situ lesions, new indolent lymphoproliferative disorders have been recently characterized. Diagnosis and characterization of these indolent lesions is necessary to prevent overtreatment with aggressive therapeutic regimens.

[Revised version of the 4th edition of the WHO classification of malignant lymphomas : What is new?]

After 8 years, the WHO has now published the updated version of the 4th edition of the classification of hematopoietic and lymphoid tumors. This update provides a conceptual rewrite of existing entities as well as some new provisional entities and categories, particularly among the aggressive B‑cell lymphomas. Important new diagnostic categories include the high-grade B‑cell lymphomas, the large B‑cell lymphoma with IRF4 rearrangement, and the Burkitt-like lymphoma with 11q aberrations. Of particular importance, new concepts concerning the taxonomy and classification of early lymphoid lesions or precursor lesions are included, such as the in situ follicular neoplasia or the in situ mantle cell neoplasia. In addition, the concept of indolent lymphoproliferations, such as breast-implant-associated anaplastic large cell lymphoma and the indolent T‑cell lymphoproliferative disorder of the gastrointestinal tract, has been strengthened. Finally, diagnostic criteria for existing lymphoma entities have been refined.