Duodenal-Type Follicular Lymphoma: A Clinicopathologic Review

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.

Lymphomas and Amyloid in the Gastrointestinal Tract

Lymphoproliferative disorders are a heterogeneous group of neoplasms with varying clinical, morphologic, immunophenotypic, and genetic characteristics. A subset of lymphomas have a proclivity for the gastrointestinal tract, although this region may also be involved by systemic lymphomas. In addition, a number of indolent lymphoproliferative disorders of the gastrointestinal tract have been defined over the past decade, and it is important to accurately differentiate these neoplasms to ensure that patients receive the proper management. Here, the authors review lymphoid neoplasms that show frequent gastrointestinal involvement and provide updates from the recent hematolymphoid neoplasm classification systems.

Diffuse large B-cell lymphoma from duodenal with hematemesis, melena, and obstruction jaundice symptoms: A rare case

INTRODUCTION

Non-Hodgkin lymphoma of the duodenum with manifestation of hematemesis, melena, and obstructive jaundice is a rare occurrence.

CASE PRESENTATION

A 47-year-old Indonesian man presented with symptoms of hematemesis of 3×/day, melena, abdominal pain, decreased appetite, and a weight loss (2 kg). The patient had symptoms of weakness, jaundice, pale conjunctiva, and experienced palpable discomfort in the epigastric region (VAS of 6). An abdominal ultrasonography revealed a heterogeneous cystic tumor mass measuring 45 × 29 mm located in the pancreas head. The gastrointestinal endoscopy revealed erosive gastritis and a tumor in the duodenum. The patient received a biliodigestive surgery and biopsy for double bypass. The pathological anatomy findings indicated the presence of non-Hodgkin lymphoma. The immunohistochemical results showed that the tumor cells were positive for CD45, CD20, and Ki67 95 % but negative for CK and CD3. The patient had a series of chemotherapy treatments include RCHOP, ICE, and EPOCH for a duration of 1½ years. Subsequently, the patient was assessed and pronounced to be cured.

DISCUSSION

The identification of diffuse large B-cell lymphoma (DLBCL) from duodenum in this case was challenging due to the presence of unspecific symptoms such as hematemesis, melena, and obstructive jaundice. Management of DLBCL involved surgical interventions and sequential chemotherapy, which have shown the most significant enhancement in prognosis.

CONCLUSION

The diagnostic accuracy of DLBCL from duodenal site enhances the effectiveness of the therapy employed, leading to a favorable prognosis.

Duodenal-Type Follicular Lymphoma

This case report presents the clinical findings, diagnostic evaluation, and treatment options for a 71-year-old female patient with a medical history of hypertension, dyslipidemia, and recurrent urinary tract infections. The patient presented with chronic abdominal pain as the sole symptom. Despite normal laboratory investigations, esophagogastroduodenoscopy and ileocolonoscopy were performed. Biopsies were obtained from the duodenum and histopathological analysis confirmed a diagnosis of duodenal-type follicular lymphoma. This rare condition typically presents with minimal clinical symptoms and has a favorable prognosis. Treatment options for duodenal-type follicular lymphoma include a watch-and-wait strategy, rituximab monotherapy, and radiotherapy.

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.

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.

Synchronous colon cancer after treatment for rectal follicular lymphoma: A case report

Colorectal follicular lymphoma (FL) is rare. In addition, it is even rarer that colon cancer develops synchronously with colorectal lymphoma. The present study reports a case of sigmoid colon cancer that developed 6 months after endoscopic resection of rectal FL. A 71-year-old man with a history of developing mucosa-associated lymphoid tissue lymphoma in his stomach at age 48, right neck region at age 59 (the latter later modified as FL) and lung adenocarcinoma at age 60 now suffers from rectal FL. Endoscopic submucosal dissection (ESD) was performed at our hospital (Aiiku Hospital), and 6 months after the treatment, sigmoid colon cancer was confirmed by colonoscopy for the follow-up study. The patient was successfully curatively resected by ESD plus local resection and has survived without a recurrence for >3 years with no treatment. It was speculated that in the present case, cancer-related genes were changed as a carcinogenic mechanism due to decreased immune function associated with the onset of lymphoma.

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

Prognostic Impact of a Body Mass Index Decrease during First Chemotherapy in Patients with Advanced Follicular Lymphoma

Objective Follicular lymphoma (FL) is an indolent B-cell malignancy, usually treated by immunochemotherapy in advanced-stage and high-tumor-burden cases. Although some reports have shown no significant relationship between the pre-treatment body mass index (BMI) and the overall survival (OS) in FL, little is known regarding BMI changes during chemotherapy. We analyzed the impact of a BMI decrease during chemotherapy on the OS in FL patients. Methods We retrospectively analyzed 56 patients with untreated advanced FL who underwent chemotherapy at our institute between July 2009 and December 2020. The BMI change was defined based on the BMI before and at three months after the first chemotherapy session. The cut-off for a BMI decrease was set at 1.42 kg/m² according to the receiver operating characteristics curve for the OS. We compared the survival outcome between two BMI groups based on this cut-off. Results A BMI decrease was significantly associated with a worse OS (5-year OS: 86.7% vs. 60.5%, p=0.019), although the pre-treatment BMI showed no significant relationship with the survival. The adverse impact of a BMI decrease remained in a multivariate analysis for the OS (hazard ratio, 3.972; p=0.045). The decreased-BMI group tended to show a higher cumulative incidence of early-onset histological transformation (HT) than the non-decreased-BMI group (20% vs. 0.0%). A BMI decrease during chemotherapy in previously untreated FL patients might reflect the hyperactivation of tumor-induced metabolism related to HT. Conclusion A BMI decrease during chemotherapy might be an independent adverse prognostic factor in FL patients. BMI changes in addition to the condition of FL patients should be monitored during chemotherapy.

Follicular lymphoma: updates for pathologists

Follicular lymphoma (FL) is the most common indolent B-cell lymphoma and originates from germinal center B-cells (centrocytes and centroblasts) of the lymphoid follicle. Tumorigenesis is believed to initiate early in precursor B-cells in the bone marrow (BM) that acquire the t(14;18)(q32;q21). These cells later migrate to lymph nodes to continue their maturation through the germinal center reaction, at which time they acquire additional genetic and epigeneticabnormalities that promote lymphomagenesis. FLs are heterogeneous in terms of their clinicopathologic features. Most FLs are indolent and clinically characterized by peripheral lymphadenopathy with involvement of the spleen, BM, and peripheral blood in a substantial subset of patients, sometimes accompanied by constitutional symptoms and laboratory abnormalities. Diagnosis is established by the histopathologic identification of a B-cell proliferation usually distributed in an at least partially follicular pattern, typically, but not always, in a lymph node biopsy. The B-cell proliferation is biologically of germinal center cell origin, thus shows an expression of germinal center-associated antigens as detected by immunophenotyping. Although many cases of FLs are typical and histopathologic features are straightforward, the biologic and histopathologic variability of FL is wide, and an accurate diagnosis of FL over this disease spectrum requires knowledge of morphologic variants that can mimic other lymphomas, and rarely non-hematologic malignancies, clinically unique variants, and pitfalls in the interpretation of ancillary studies. The overall survival for most patients is prolonged, but relapses are frequent. The treatment landscape in FL now includes the application of immunotherapy and targeted therapy in addition to chemotherapy.

Duodenal-type follicular lymphoma -a silent tumor

A 79-year-old male, with a past medical history of hypertension, dyslipidemia and type 2 diabetes, underwent routine esophagogastroduodenoscopy and colonoscopy. The patient was asymptomatic, with unremarkable blood tests. Upper gastrointestinal endoscopy showed multiple whitish nodular lesions in the first part of the duodenum.

A rare case of duodenal-type follicular lymphoma in rectum appearing as hyperplastic polyp with metachronous appearance in duodenum and stomach

Hyperplastic polyps consist a very frequent finding in colonoscopy having a very low potential to malignancy. According to the international guidelines, it is recommended that all polyps should be resected except for diminutive (≤ 5 mm) rectal and rectosigmoid polyps which are predicted with confidence to be hyperplastic. Therefore, in departments where optical diagnosis can be ensured, a "resect and discard" strategy may be implemented for diminutive polyps. In our case, a duodenal-type follicular lymphoma was detected in a 5 mm rectum polyp with hyperplastic appearance. After 4 months, the lymphoma was detected also in stomach and duodenum. Under therapy with Rituximab, she is in remission. To our knowledge, there has never been reported such a case in the literature. Furthermore, it alerts us that we should be very cautious with the optical diagnosis and the "resect and discard strategy".

Gastrointestinal lymphoproliferative lesions: a practical diagnostic approach

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

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

Follicular Lymphoma Presenting as Intussusception in an Adult

A 61-year-old male with no past medical history presented with intense abdominal pain for three days, associated with hematochezia, nausea, and non-bloody vomiting. CT scan of the abdomen showed distended small bowel, diffuse lymphadenopathy, and intussusception of the distal ileum into the cecum with obstruction. Ileocolic resection and histopathological staining confirmed the diagnosis of follicular lymphoma and appropriate treatment was initiated. Intussusception is a condition that involves the invagination of the proximal segment of a bowel tract into its contiguous distal segment as a result of enthusiastic or impaired peristalsis. Only 5% of the total intussusception cases are found in adults. Most cases in adults are caused by pathological lead points which can be benign or malignant. Lymphomas rarely present with intussusception and follicular lymphomas are even less common. To the best of our knowledge, there have only been a few such cases of follicular lymphomas with the initial presentation of intussusception. In this article, we present a rare case of follicular lymphoma presenting as intussusception. Considering lymphomas as a cause of intussusception in adults can decrease diagnostic delays and guide treatment.

Recent Advances in Digestive Tract Tumors: Updates From the 5th Edition of the World Health Organization "Blue Book"

CONTEXT.—

The World Health Organization Classification of Tumours: Digestive System Tumors, 5th edition, was published in 2019 and shows several impactful changes as compared with the 4th edition published in 2010. Changes include a revised nomenclature of serrated lesions and revamping the classification of neuroendocrine neoplasms. Appendiceal goblet cell adenocarcinoma is heavily revised, and intrahepatic cholangiocarcinoma is split into 2 subtypes. New subtypes of colorectal carcinoma and hepatocellular carcinoma are described. Precursor lesions are emphasized with their own entries, and both dysplastic and invasive lesions are generally recommended to be graded using a 2-tier system. Hematolymphoid tumors, mesenchymal tumors, and genetic tumor syndromes each have their own sections in the 5th edition. New hematolymphoid lesions include monomorphic epitheliotropic intestinal T-cell lymphoma; duodenal-type follicular lymphoma; intestinal T-cell lymphoma, not otherwise specified; and indolent T-cell lymphoproliferative disorder of the gastrointestinal tract. This paper will provide an in-depth look at the changes in the 5th edition as compared with the 4th edition.

OBJECTIVE.—

To provide a comprehensive, in-depth update on the World Health Organization classification of digestive tumors, including changes to nomenclature, updated diagnostic criteria, and newly described entities.

DATA SOURCES.—

The 5th edition of the World Health Organization Classification of Tumours: Digestive System Tumours, as well as the 4th edition.

CONCLUSIONS.—

The World Health Organization has made many key changes in its newest update on tumors of the digestive system. Pathologists should be aware of these changes and incorporate them into their practice as able or necessary.

B Cell Lymphomas of the GI Tract

PURPOSE OF THE REVIEW

Primary GI lymphomas of B cell origin are a diverse group of lymphomas. In this article, we provide an overview of the diagnosis, pathologic and molecular features, and management of these varied lymphomas.

RECENT FINDINGS

The most common primary GI lymphomas are diffuse large B cell lymphoma (DLBCL) and marginal zone lymphomas (MZL), but follicular lymphomas (FL), mantle cell lymphomas (MCL), post-transplant lymphoproliferative disorders (PTLD), and Burkitt lymphoma of the GI tract also occur. Many features of these lymphomas are similar to their nodal counterparts, but certain clinical and biological aspects are unique. Diagnostic and treatment strategies for these lymphomas continue to evolve over time. There are ongoing discoveries about the unique pathophysiology, molecular characteristics, and complications of primary B cell GI lymphomas that are already leading to improvements in management of this histologically diverse set of lymphomas.

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.

Overview of Gastrointestinal Lymphoproliferative disorders✰

Lymphoproliferative processes which occur in the gastrointestinal tract range from benign reactive processes such as follicular hyperplasia (rectal tonsil) to high grade malignant lymphomas and histiocytic sarcoma. The WHO Classification of Tumors: Digestive System Tumors, 5th Edition was published in 2019 and shows several impactful changes as compared to the 4th Edition published in 2010. WHO Classification of Tumors of Hematopoietic and Lymphoid Tissues 2017 also included detailed changes in hematopoietic neoplasms within the gastrointestinal tract. New entities or renamed hematolymphoid lesions include monomorphic epitheliotropic intestinal T-cell lymphoma, duodenal-type follicular lymphoma, intestinal T-cell lymphoma, NOS and indolent T-cell lymphoproliferative disorder of the gastrointestinal tract. A brief overview of WHO classification of digestive tumors and WHO classification of tumors of hematopoietic and lymphoid tissue is discussed focusing on the changes in the most recent WHO texts. In depth discussions will be presented in other papers in this series.

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.

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.

Follicular lymphoma

Follicular lymphoma (FL) is a systemic neoplasm of the lymphoid tissue displaying germinal centre (GC) B cell differentiation. FL represents ~5% of all haematological neoplasms and ~20-25% of all new non-Hodgkin lymphoma diagnoses in western countries. Tumorigenesis starts in precursor B cells and becomes full-blown tumour when the cells reach the GC maturation step. FL is preceded by an asymptomatic preclinical phase in which premalignant B cells carrying a t(14;18) chromosomal translocation accumulate additional genetic alterations, although not all of these cells progress to the tumour phase. FL is an indolent lymphoma with largely favourable outcomes, although a fraction of patients is at risk of disease progression and adverse outcomes. Outcomes for FL in the rituximab era are encouraging, with ~80% of patients having an overall survival of >10 years. Patients with relapsed FL have a wide range of treatment options, including several chemoimmunotherapy regimens, phosphoinositide 3-kinase inhibitors, and lenalidomide plus rituximab. Promising new treatment approaches include epigenetic therapeutics and immune approaches such as chimeric antigen receptor T cell therapy. The identification of patients at high risk who require alternative therapies to the current standard of care is a growing need that will help direct clinical trial research. This Primer discusses the epidemiology of FL, its molecular and cellular pathogenesis and its diagnosis, classification and treatment.

[Histopathological classification of chronic B-lymphoproliferative disorders]

Chronic lymphoproliferative disorders should be classified according to the revised 2016 WHO classification. Biopsies are not mandatory for all chronic lymphoproliferative disorders as blood or bone marrow cytologroachical approach can be sufficient for some lymphoma entities. Diagnostic is based on a multidiscplinary approach taking into account clinical presentation, histopathological, cytological, immunophenotypical features (immunohistochemistry and Flow cytometry) and molecular pattern (translocation by FISH, Mutations landscape by NGS, and genomic abnormalities by CGH array). An important heterogeneity of clinical presentation and prognosis arises within the same lymphoma subtype. Clinical evolution is characterized by relapses, cytological progression and transformation into diffuse large B cell lymphoma, aggressive lymphoma or high-grade lymphomas.

[Follicular lymphoma: An update]

Follicular lymphoma, the second most common lymphoma, is characterized by its slow growth and is often considered incurable in advanced stages. Progresses in biology have contributed to better understand the complex and successive mechanisms of development of this pathology, whose diagnosis is based on a lymph node biopsy. However, the prognosis of the patients is heterogeneous and several indexes have been proposed to identify groups of patients with a similar life expectancy, in order to guide the therapeutic choices. The treatment has been modified in the last 20 years by the emergence of anti-CD20 monoclonal antibodies which constitute, alone or in combination, of the cornerstone of therapeutic management. After staging using, in particular, 18-fluorodeoxyglucose positron emission tomography, the therapeutic strategy will be adapted for each patient, ranging from simple watchful waiting to a combination of chemotherapy and anti-CD20 antibodies. Relapses (which often require a new lymph node biopsy to eliminate a possible histological transformation into an aggressive lymphoma with poorer prognosis) remain common but are still accessible to effective therapeutic interventions. Thanks to these advances, the median life expectancy of patients with follicular lymphoma now exceeds 15 years.