Prognostic relevance of circulating lymphoma cells at diagnosis in newly diagnosed follicular lymphoma patients.

Follicular lymphoma (FL) is the most common indolent B-cell non-Hodgkin lymphoma. Circulating lymphoma (CL) cells can be seen at diagnosis in some FL patients, however, previous studies evaluating this have shown mixed results. Therefore, we sought to evaluate the impact of CL at diagnosis on outcomes in patients with newly diagnosed FL using data from a single center. Patients were divided into CL+ and CL- based on immunophenotyping via peripheral blood (PB) flow cytometry. CL was defined as detectable clonally restricted B-cells that matched the actual or expected B-cell immunophenotype of FL. The primary endpoint was progression-free survival (PFS) after first-line treatment and secondary endpoints included overall response rate (ORR), overall survival (OS), diagnosis to treatment interval (DTI), progression of disease within 2 years of diagnosis (POD24), and cumulative incidence of transformation between the two groups. Among the 541 patients with FL, 204 had PB flow cytometry performed at diagnosis, and after excluding patients not meeting the eligibility criteria, 147 cases remained with 24 (16%) CL+ at diagnosis. Patients in the CL+ group were younger (53 vs. 58 years, p = 0.02), had more extranodal involvement (83% vs. 44%, p < 0.01), follicular lymphoma international prognostic index 3-5 (55% vs. 31%, p = 0.01), and a higher proportion received first-line immunochemotherapy (75% vs. 43%, p = 0.01) compared to the CL-group. The median PFS was not significantly different between CL+ (6.27 years, 95% CI = 3.61-NR) and CL- (6.61 years, 95% CI = 5.10-9.82) cohorts regardless of the first-line treatment or level of absolute PB CL cells. There was no significant difference in ORR, median OS, DTI, POD24, and cumulative incidence of transformation between the two groups. In our study, we found that the presence of CL cells at diagnosis in FL in the contemporary era did not impact outcomes and survival.

Patient-derived follicular lymphoma spheroids recapitulate lymph node signaling and immune profile uncovering galectin-9 as a novel immunotherapeutic target.

Follicular lymphoma (FL), the most common indolent non-Hodgkin lymphoma, constitutes a paradigm of immune tumor microenvironment (TME) contribution to disease onset, progression, and heterogenous clinical outcome. Here we present the first FL-Patient Derived Lymphoma Spheroid (FL-PDLS), including fundamental immune actors and features of TME in FL lymph nodes (LNs). FL-PDLS is organized in disc-shaped 3D structures composed of proliferating B and T cells, together with macrophages with an intermediate M1/M2 phenotype. FL-PDLS recapitulates the most relevant B-cell transcriptional pathways present in FL-LN (proliferation, epigenetic regulation, mTOR, adaptive immune system, among others). The T cell compartment in the FL-PDLS preserves CD4 subsets (follicular helper, regulatory, and follicular regulatory), also encompassing the spectrum of activation/exhaustion phenotypes in CD4 and CD8 populations. Moreover, this system is suitable for chemo and immunotherapy testing, recapitulating results obtained in the clinic. FL-PDLS allowed uncovering that soluble galectin-9 limits rituximab, rituximab, plus nivolumab/TIM-3 antitumoral activities. Blocking galectin-9 improves rituximab efficacy, highlighting galectin-9 as a novel immunotherapeutic target in FL. In conclusion, FL-PDLS maintains the crosstalk between malignant B cells and the immune LN-TME and constitutes a robust and multiplexed pre-clinical tool to perform drug screening in a patient-derived system, advancing toward personalized therapeutic approaches.

Follicular lymphoma regulatory T-cell origin and function.

Introduction: Follicular Lymphoma (FL) results from the malignant transformation of germinal center (GC) B cells. FL B cells display recurrent and diverse genetic alterations, some of them favoring their direct interaction with their cell microenvironment, including follicular helper T cells (Tfh). Although FL-Tfh key role is well-documented, the impact of their regulatory counterpart, the follicular regulatory T cell (Tfr) compartment, is still sparse. Methods: The aim of this study was to characterize FL-Tfr phenotype by cytometry, gene expression profile, FL-Tfr origin by transcriptomic analysis, and functionality by in vitro assays. Results: CD4+CXCR5+CD25hiICOS+ FL-Tfr displayed a regulatory program that is close to classical regulatory T cell (Treg) program, at the transcriptomic and methylome levels. Accordingly, Tfr imprinting stigmata were found on FL-Tfh and FL-B cells, compared to their physiological counterparts. In addition, FL-Tfr co-culture with autologous FL-Tfh or cytotoxic FL-CD8+ T cells inhibited their proliferation in vitro. Finally, although FL-Tfr shared many characteristics with Treg, TCR sequencing analyses demonstrated that part of them derived from precursors shared with FL-Tfh. Discussion: Altogether, these findings uncover the role and origin of a Tfr subset in FL niche and may be useful for lymphomagenesis knowledge and therapeutic management.

Observation of lymphadenopathy, systemic symptoms, and treatment in suspected indolent cutaneous B-cell lymphomas.

BACKGROUND: Following the initial diagnosis of a marginal zone or follicle center lymphoma on skin biopsy, patients undergo staging to determine the extent of disease. OBJECTIVE: We sought to characterize the frequency that these patients were found to have a systemic nodal disease upon work-up as well as the impact of imaging on disease management. METHODS: We conducted a retrospective chart review of patients presenting with a working diagnosis of PCMZL or PCFCL treated at The Ohio State University from 1990 to 2022. Data collected included: patient history, progress notes, virtual encounters, laboratory results, presentation features, imaging, and pathology. Biomarkers included ANA, SSA/SSB, BCL6 and H. Pylori labs, bone marrow biopsies, positive imaging, and need of systemic medication and mortality. RESULTS: 71 patients with suspected PCMZL and PCFCL were identified. 66 of 71 patients underwent imaging. Of this group, 12 patients (9 with suspected PCFCL and 3 with suspected PCMZL) demonstrated lymphadenopathy on imaging. Of these 12 patients, 5 underwent biopsy of suspected lymph nodes, and 3 had biopsy-proven nodal involvement and received systemic therapy. Of the remaining 7 patients with evidence of lymphadenopathy on imaging, 4 were thought to have reactive lymph nodes, and 3 were treated empirically with systemic chemotherapy due to the extent or progression of their disease. Of patients with imaging negative for lymphadenopathy, 3 of 52 (5.8%) patients with received systemic treatment, while 49 of 52 patients (94.2%) received localized treatment. LIMITATIONS: Most of the relationships between this data were correlational and patients selected for this study were limited to a single institution. CONCLUSION: Prospective study of the role of imaging without subsequent lymph biopsy to direct treatment decisions is warranted.

Thyroid papillary carcinoma combined with primary follicular lymphoma: a case report.

BACKGROUND: Papillary thyroid carcinoma (PTC) stands out as the most prevalent epithelial malignant thyroid tumor. Thyroid primary follicular lymphoma (PFL) represents a rare malignant tumor originating from mesenchymal tissues. The concurrent occurrence of PTC and PFL is exceptionally rare, particularly in the context of Hashimoto's thyroiditis, presenting significant challenges in clinical diagnosis and treatment. CASE DEMONSTRATION: A 44-year-old female patient presented with a neck mass persisting for over 1 month. The patient underwent surgery, and the incised tissues were subjected to pathology examinations, along with immunohistochemistry and next-generation sequencing tests suggestive of an EZH2 gene mutation in the tumor cells. The final pathological diagnosis confirmed the presence of PTC combined with PFL. Following a 27-month follow-up, the patient displayed no signs of recurrence or metastasis. CONCLUSIONS: The concurrent occurrence of PTC and PFL poses notable challenges in clinical practice, requiring careful consideration in diagnosis and treatment. Herein, we present a rare case of PTC combined with PFL featuring an EZH2 gene mutation, which can be easily overlooked in the context of Hashimoto's thyroiditis. The patient's favorable response to surgical and radiotherapeutic interventions underscores the importance of accurate diagnosis and tailored treatment strategies in similar cases.

MNDA expression and its value in differential diagnosis of B-cell non-Hodgkin lymphomas: a comprehensive analysis of a large series of 1293 cases.

AIMS: MNDA (myeloid nuclear differentiation antigen) has been considered as a potential diagnostic marker for marginal zone lymphoma (MZL), but its utility in distinguishing MZL from other B-cell non-Hodgkin lymphomas (B-NHLs) and its clinicopathologic relevance in diffuse large B-cell lymphoma (DLBCL) are ambiguous. We comprehensively investigated MNDA expression in a large series of B-NHLs and evaluated its diagnostic value. METHODS: MNDA expression in a cohort of 1293 cases of B-NHLs and 338  cases of reactive lymphoid hyperplasia (RLH) was determined using immunohistochemistry and compared among different types of B-NHL. The clinicopathologic relevance of MNDA in DLBCL was investigated. RESULTS: MNDA was highly expressed in MZLs (437/663, 65.9%), compared with the confined staining in marginal zone B-cells in RLH; whereas neoplastic cells with plasmacytic differentiation lost MNDA expression. MNDA expression was significantly higher in mantle cell lymphoma (MCL, 79.6%, p = 0.006), whereas lower in chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL, 44.8%, p = 0.001) and lymphoplasmacytic lymphoma (LPL, 25%, p = 0.016), and dramatically lower in follicular lymphoma (FL, 5.2%, p < 0.001), compared with MZL. 29.6% (63/213) of DLBCLs were positive for MNDA. The cases in non-GCB group exhibited a higher rate of MNDA positivity (39.8%) compared to those in GCB group (16.3%) (p < 0.001), and MNDA staining was more frequently observed in DLBCLs with BCL2/MYC double-expression (50%) than those without BCL2/MYC double-expression (24.8%) (p = 0.001). Furthermore, there was a significant correlation between MNDA and CD5 expression in DLBCL (p = 0.036). CONCLUSIONS: MNDA was highly expressed in MZL with a potential utility in differential diagnosis between MZL and RLH as well as FL, whereas its value in distinguishing MZL from MCL, CLL/SLL is limited. In addition, MNDA expression in DLBCL was more frequently seen in the non-GCB group and the BCL2/MYC double-expression group, and demonstrated a correlation with CD5, which deserves further investigation. The clinical relevance of MNDA and its correlation with the prognosis of these lymphomas also warrant to be fully elucidated.

Anthropometric indicators may explain the high incidence of follicular lymphoma in Europeans: Results from a bidirectional two-sample two-step Mendelian randomisation.

BACKGROUND: Non-Hodgkin's lymphoma incidence rates vary between European and Asian populations. The reasons remain unclear. This two-sample two-step Mendelian randomisation (MR) study aimed to investigate the causal relationship between anthropometric indicators (AIs) and diffuse large B-cell lymphoma (DLBCL) and follicular lymphoma (FL) and the possible mediating role of basal metabolic rate (BMR) in Europe. METHODS: We used the following AIs as exposures: body mass index (BMI), whole-body fat mass (WBFM), whole-body fat-free mass (WBFFM), waist circumference(WC), hip circumference(HC), standing height (SH), and weight(Wt). DLBCL and FL represented the outcomes, and BMR was a mediator. A two-sample MR analysis was performed to examine the association between AIs and DLBCL and FL onset. We performed reverse-MR analysis to determine whether DLBCL and FL interfered with the AIs. A two-step MR analysis was performed to determine whether BMR mediated the causality. FINDINGS: WBFFM and SH had causal relationships with FL. A causal association between AIs and DLBCL was not observed. Reverse-MR analysis indicated the causal relationships were not bidirectional. Two-step MR suggested BMR may mediate the causal effect of WBFFM and SH on FL. CONCLUSIONS: We observed a causal relationship between WBFFM and SH and the onset of FL in Europeans, Which may explain the high incidence of follicular lymphoma in Europeans.

Disseminated Enterovirus Infection in a Patient Affected by Follicular Lymphoma Treated with Obinutuzumab: A Case Report and a Narrative Review of the Literature.

Background and Objectives: the principal purpose of this literature review is to cluster adults with hematological malignancies after treatment or on maintenance with obinutuzumab who experienced disseminated EV infection to understand clinical characteristics and outcome of this rare condition in these patients. We report the first clinical case of a male affected by follicular lymphoma treated with immune-chemotherapy including obinutuzumab who was affected by disseminated EV infection with cardiovascular involvement. Materials and Methods: this narrative review summarizes all the research about disseminated EV infection in immunosuppressed adult patients treated with obinutuzumab from January 2000 to January 2024 using the Scale for the Assessment of Narrative Review Articles (SANRA) flow-chart. We performed a descriptive statistic using the standard statistical measures for quantitative data. Results: we included six studies, five case reports, and one case report with literature analysis. We collected a total of seven patients, all female, with disseminated EV infection. The most common signs and clinical presentations of EV infection were fever and encephalitis symptoms (N = 6, 85.7%), followed by hepatitis/acute liver failure (N = 5, 71.4%). Conclusions: onco-hematological patients who receive immune-chemotherapy with a combination of treatments which depress adaptative immunity, which includes the antiCD20 obinutuzumab, could be at higher risk of disseminated EV infection, including CNS and cardiac involvement.

Follicular lymphoma B cells exhibit heterogeneous transcriptional states with associated somatic alterations and tumor microenvironments.

Follicular lymphoma (FL) is an indolent non-Hodgkin lymphoma of germinal center origin, which presents with significant biologic and clinical heterogeneity. Using RNA-seq on B cells sorted from 87 FL biopsies, combined with machine-learning approaches, we identify 3 transcriptional states that divide the biological ontology of FL B cells into inflamed, proliferative, and chromatin-modifying states, with relationship to prior GC B cell phenotypes. When integrated with whole-exome sequencing and immune profiling, we find that each state was associated with a combination of mutations in chromatin modifiers, copy-number alterations to TNFAIP3, and T follicular helper cells (Tfh) cell interactions, or primarily by a microenvironment rich in activated T cells. Altogether, these data define FL B cell transcriptional states across a large cohort of patients, contribute to our understanding of FL heterogeneity at the tumor cell level, and provide a foundation for guiding therapeutic intervention.

Mutational, immune microenvironment, and clinicopathological profiles of diffuse large B-cell lymphoma and follicular lymphoma with BCL6 rearrangement.

BCL6-rearrangement (BCL6-R) is associated with a favorable prognosis of follicular lymphoma (FL), but the mechanism is unknown. We analyzed the clinicopathological, immune microenvironment (immune checkpoint, immuno-oncology markers), and mutational profiles of 10 BCL6-R-positive FL, and 19 BCL6-R-positive diffuse large B-cell lymphoma (DLBCL) cases (both BCL2-R and MYC-R negative). A custom-made panel included 168 genes related to aggressive B-cell lymphomas and FL. FL cases were nodal, histological grade 3A in 70%, low Ki67; and had a favorable overall and progression-free survival. DLBCL cases were extranodal in 60%, IPI high in 63%, non-GCB in 60%, EBER-negative; and had a progression-free survival comparable to that of DLBCL NOS. The microenvironment had variable infiltration of M2-like tumor-associated macrophages (TAMs) that were CD163, CSF1R, LAIR1, PD-L1, and CD85A (LILRB3) positive; but had low IL10 and PTX3 expression. In comparison to FL, DLBCL had higher TAMs, IL10, and PTX3 expression. Both lymphoma subtypes shared a common mutational profile with mutations in relevant pathogenic genes such as KMT2D, OSBPL10, CREBBP, and HLA-B (related to chromatin remodeling, metabolism, epigenetic modification, and antigen presentation). FL cases were characterized by a higher frequency of mutations of ARID1B, ATM, CD36, RHOA, PLOD2, and PRPRD (p < 0.05). DLBCL cases were characterized by mutations of BTG2, and PIM1; and mutations of HIST1H1E and MFHAS1 to disease progression (p < 0.05). Interestingly, mutations of genes usually associated with poor prognosis, such as NOTCH1/2 and CDKN2A, were infrequent in both lymphoma subtypes. Some high-confidence variant calls were likely oncogenic, loss-of-function. MYD88 L265P gain-of-function was found in 32% of DLBCL. In conclusion, both BCL6-R-positive FL and BCL6-R-positive DLBCL had a common mutational profile; but also, differences. DLBCL cases had a higher density of microenvironment markers.

Profiling of Copy Number Alterations Using Low-Coverage Whole-Genome Sequencing Informs Differential Diagnosis and Prognosis in Primary Cutaneous Follicle Center Lymphoma.

Primary cutaneous follicle center lymphoma (PCFCL) has an excellent prognosis using local treatment, whereas nodal follicular lymphoma (nFL), occasionally presenting with cutaneous spread, often requires systemic therapy. Distinction of the 2 diseases based on histopathology alone might be challenging. Copy number alterations (CNAs) have scarcely been explored on a genome-wide scale in PCFCL; however, they might serve as potential biomarkers during differential diagnosis and risk stratification. Low-coverage whole-genome sequencing is a robust, high-throughput method for genome-wide copy number profiling. In this study, we analyzed 28 PCFCL samples from 20 patients and compared the copy number profiles with a cohort of diagnostic samples of 64 nFL patients. Although the copy number profile of PCFCL was similar to that of nFL, PCFCL lacked amplifications of 18q, with the frequency peaking at 18q21.33 in nFL cases involving the BCL2 locus (PCFCL: 5.0% vs nFL: 31.3%, P = .018, Fisher exact test). Development of distant cutaneous spread was significantly associated with higher genomic instability including the proportion of genome altered (0.02 vs 0.13, P = .033) and number of CNAs (2 vs 9 P = .017), as well as the enrichment of 2p22.2-p15 amplification involving REL and XPO1 (6.3% vs 60.0%, P = .005), 3q23-q24 amplification (0.0% vs 50.0%, P = .004), 6q16.1-q23.3 deletion (6.3% vs 50.0%, P = .018), and 9p21.3 deletion covering CDKN2A and CDKN2B loci (0.0% vs 40.0%, P = .014, all Fisher exact test) in PCFCL. Analysis of sequential tumor samples in 2 cases harboring an unfavorable clinical course pointed to the acquisition of 2p amplification in the earliest common progenitor underlining its pivotal role in malignant transformation. By performing genome-wide copy number profiling on the largest patient cohort to date, we identified distinctive CNA alterations conceivably facilitating the differential diagnosis of PCFCL and secondary cutaneous involvement of nFL and potentially aiding the risk stratification of patients with PCFCL in the future.

A case of concurrent follicular lymphoma and lung cancer requiring differentiation from lymph node metastasis.

Lung cancer complicated by follicular lymphoma has rarely been reported in the literature. A 69-year-old male with an abnormal shadow on a chest radiograph was referred to our hospital. A mass in the right lung was seen on chest computed tomography (CT). Positron emission tomography-CT showed fluorodeoxyglucose accumulation in the esophagus and multiple intra-abdominal lymph nodes, in addition to the right lung lesion. The lung lesion was diagnosed as a pulmonary adenocarcinoma after biopsy. Upper and lower gastrointestinal endoscopies did not reveal the presence of a tumor. Open lymph node biopsy was performed to determine the course of treatment, leading to a diagnosis of follicular lymphoma. The patient finally underwent radical resection for lung cancer; the follicular lymphoma was judged to be low-grade and was followed up. When complications involving other organs are detected during systemic examination of a patient with lung cancer, it is necessary to distinguish between metastasis to other organs and complications of other malignant diseases, as this will greatly influence the treatment strategy.

Potential genetic mechanisms driving B/myeloid conversion in patients with follicular lymphoma and Langerhans cell neoplasms.

Transformation of follicular lymphoma (FL) to a Langerhans cell (LC) neoplasm is extremely uncommon. The shared IGH::BCL2 rearrangement is a robust finding in most transformed tumors underscoring that the cell of origin is perhaps a pre-B cell harboring IGH::BCL2 with the propensity to undergo further genetic alterations in the germinal centers of lymph nodes: does IGH::BCL2 in pre-B cells set off a plasticity cell state? Do FL and LC neoplasms develop separately through a common progenitor or via a multistep process of transdifferentiation or dedifferentiation/redifferentiation? Here, we review the literature and relevant cases presented in the Society for Hematopathology/European Association of Haematopathology 2021 Workshop to better understand this rare and complex phenomenon. We discuss clinical data, clonal relationship, and the mutational profile of these tumors and review proposed mechanisms of B/myeloid conversion based on in vitro and in vivo models.

Plasmablastic transformation of a double hit follicular lymphoma: An emerging entity.

ABSTRACT: Plasmablastic transformation of follicular lymphoma is very rare and has been reported in only 5 cases till date. We report a case of simultaneous identification of extranodal, soft tissue plasmablastic lymphoma in the ankle and bone marrow involvement by follicular lymphoma. This unusual case presentation is a challenge for the treating physician with the patient becoming resistant to chemotherapy and succumbing to the disease within a few months of diagnosis. These cases are known to have an aggressive clinical course with very poor prognosis and survival rate of less than 6 months. This report broadens the spectrum of morphological transformation of follicular lymphoma and it may represent a new category of high-grade transformation of follicular lymphoma.

Follicular Lymphoma Presenting With Symptomatic Bone Involvement: A Clinicopathologic and Molecular Analysis of 16 Cases.

Primary bone lymphoma (PBL) is rare and mostly represented by diffuse large B-cell lymphomas (DLBCL). Follicular lymphoma (FL), albeit commonly disseminating to the bone marrow, rarely presents primarily as bone lesions. Here, we studied 16 patients (12 men:4 women, median age 60 years) who presented with bone pain and/or skeletal radiologic abnormalities revealing bone FL. Lesions were multifocal in 11 patients (spine ± appendicular skeleton), and unifocal in 5 patients (femoral, tibial, or vertebral). An infiltrate of centrocytes and centroblasts (CD20+ CD5- CD10+ BCL2+ BCL6+) with abundant reactive T cells and an increased reticulin fibrosis massively replaced the marrow spaces between preserved bone trabeculae. The pattern was diffuse ± nodular, often with paratrabecular reinforcement and/or peripheral paratrabecular extension. Ki-67 was usually <15%. Two cases had necrosis. BCL2 rearrangement was demonstrated in 14 of 14 evaluable cases (with concomitant BCL6 rearrangement in one). High-throughput sequencing revealed BCL2, KMT2D, and TNFRSF14 to be the most frequently mutated genes. After staging, 5 qualified for PBL (3 limited stage) and 11 had stage IV systemic FL. All patients received rituximab ± polychemotherapy as firstline treatment, and 7 received local therapy (6 radiotherapy and 2 surgery). Three patients experienced transformation to DLBCL. At the last follow-up (15/16, median 48 months), 11 patients achieved complete remission, including all cases with PBL and most patients with limited extraosseous disease (3-year progression-free survival 71%). One patient died of unrelated cause (3-year overall survival 91%). FL may manifest as a localized or polyostotic bone disease. A minority represent PBL, whereas most reveal systemic disease.

The follicular lymphoma tumor microenvironment at single-cell and spatial resolution.

ABSTRACT: Follicular lymphoma (FL) is a generally incurable malignancy that originates from developmentally blocked germinal center B cells residing, primarily, within lymph nodes (LNs). During the long natural history of FL, malignant B cells often disseminate to multiple LNs and can affect virtually any organ. Nonmalignant LNs are highly organized structures distributed throughout the body, in which they perform functions critical for host defense. In FL, the malignant B cells "re-educate" the lymphoid environment by altering the phenotype, distribution, and abundance of other cells such as T cells, macrophages, and subsets of stromal cells. Consequently, dramatic anatomical changes occur and include alterations in the number, shape, and size of neoplastic follicles with an accompanying attenuation of the T-cell zone. Ongoing and dynamic interactions between FL B cells and the tumor microenvironment (TME) result in significant clinical heterogeneity observed both within and across patients. Over time, FL evolves into pathological variants associated with distinct outcomes, ranging from an indolent disease to more aggressive clinical courses with early death. Given the importance of both cell-intrinsic and -extrinsic factors in shaping disease progression and patient survival, comprehensive examination of FL tumors is critical. Here, we describe the cellular composition and architecture of normal and malignant human LNs and provide a broad overview of emerging technologies for deconstructing the FL TME at single-cell and spatial resolution. We additionally discuss the importance of capturing samples at landmark time points as well as longitudinally for clinical decision-making.

[Follicular lymphoma with a predominantly diffuse growth pattern with 1p36 deletion: a clinicopathologic analysis of eight cases].

Objective: To investigate the clinical and pathologic features and diagnosis of follicular lymphoma (FL) with a predominantly diffuse growth pattern (DFL) with 1p36 deletion. Methods: Eight cases of DFL with 1p36 deletion diagnosed at Department of Pathology, Beijing Friendship Hospital, Capital Medical University (n=5) and the Affiliated Cancer Hospital of Zhengzhou University, Henan Cancer Hospital (n=3) from January 2017 to January 2023 were included. Their clinicopathologic features and follow-up data were analyzed. Immunohistochemistry and fluorescence in situ hybridization (FISH) were performed. Results: There were five males and three females, with a median age of 67 years, and inguinal lymphadenopathy was found as the main symptom. Histologically, similar morphologic features were sheared among all cases, with effaced nodal structure and characterized by proliferation of centrocytes in a diffuse pattern, with or without follicular components. The germinal center-related markers such as CD10 and/or bcl-6 were expressed in the tumor cells, and 1p36 deletion but not bcl-2 translocation was appreciable in these cases. Conclusions: DFL with 1p36 deletion is a rare subtype of FL, with some overlaps with other types of FL or indolent B-cell lymphomas in their pathologic features. An accurate diagnosis requires comprehensive considerations based on their clinical, pathologic, immunohistochemical, and molecular features.

Diagnosis of chronic B-cell lymphoproliferative disease in peripheral blood = how machine learning may help to the interpretation of flow cytometry data.

Flow cytometry (FCM) has become a method of choice for immunologic characterization of chronic lymphoproliferative disease (CLPD). To reduce the potential subjectivities of FCM data interpretation, we developed a machine learning random forest algorithm (RF) allowing unsupervised analysis. This assay relies on 16 parameters obtained from our FCM screening panel, routinely used in the exploration of peripheral blood (PB) samples (mean fluorescence intensity values (MFI) of CD19, CD45, CD5, CD20, CD200, CD23, HLA-DR, CD10 in CD19-gated B cells, ratio of kappa/Lambda, and different ratios of MFI B-cells/T-cells [CD20, CD200, CD23]). The RF algorithm was trained and validated on a large cohort of more than 300 annotated different CLPD cases (chronic B-cell leukemia, mantle cell lymphoma, marginal zone lymphoma, follicular lymphoma, splenic red pulp lymphoma, hairy cell leukemia) and non-tumoral selected from PB samples. The RF algorithm was able to differentiate tumoral from non-tumoral B-cells in all cases and to propose a correct CLPD classification in more than 90% of cases. In conclusion the RF algorithm could be proposed as an interesting help to FCM data interpretation allowing a first B-cells CLPD diagnostic hypothesis and/or to guide the management of complementary analysis (additional immunologic markers and genetic).