Splenic Diffuse Red Pulp Lymphoma Research Articles

Hairy cell leukemia 2024: Update on diagnosis, risk-stratification, and treatment-Annual updates in hematological malignancies.

Hairy cell leukemia (HCL) and HCL-like disorders, including HCL variant (HCL-V) and splenic diffuse red pulp lymphoma (SDRPL), are a very heterogenous group of mature lymphoid B-cell disorders characterized by the identification of hairy cells, a specific genetic profile, a different clinical course and the need for appropriate treatment. Diagnosis of HCL is based on morphological evidence of hairy cells, an HCL immunologic score of 3 or 4 based on the CD11c, CD103, CD123, and CD25 expression, the trephine biopsy which makes it possible to specify the degree of tumoral bone marrow infiltration and the presence of BRAFV600E somatic mutation. Progression of patients with HCL is based on a large splenomegaly, leukocytosis, a high number of hairy cells in the peripheral blood, and the immunoglobulin heavy chain variable region gene mutational status. VH4-34 positive HCL cases are associated with a poor prognosis, as well as HCL with TP53 mutations and HCL-V. Patients should be treated only if HCL is symptomatic. Chemotherapy with risk-adapted therapy purine analogs (PNAs) are indicated in first-line HCL patients. The use of chemo-immunotherapy combining cladribine (CDA) and rituximab (R) represents an increasingly used therapeutic approach. Management of relapsed/refractory disease is based on the use of BRAF inhibitors (BRAFi) plus R, MEK inhibitors (MEKi), recombinant immunoconjugates targeting CD22, Bruton tyrosine kinase inhibitors (BTKi), and Bcl-2 inhibitors (Bcl-2i). However, the optimal sequence of the different treatments remains to be determined.

Untangling hairy cell leukaemia (HCL) variant and other HCL-like disorders: Diagnosis and treatment.

The variant form of hairy cell leukaemia (HCL-V) is a rare disease very different from hairy cell leukaemia (HCL), which is a very well-defined entity. The 5th WHO edition (Leukemia, 36, 2022 and 1720) classification (WHO-HAEM5) introduced splenic lymphomas/leukaemias including four different entities: (1) HCL, (2) splenic marginal zone lymphoma (SMZL) with circulating villous cells in the peripheral blood, (3) splenic lymphoma with prominent nucleolus (SLPN), which replaced HCL-V and CD5 negative B-prolymphocytic leukaemia (B-PLL), and (4) splenic diffuse red pulp lymphoma (SDRPL). All these entities have to be distinguished because of a different clinical course and the need for a different treatment. The diagnosis can be challenging because of complex cases and overlap and/or grey zones between all the entities and needs integrating clinical, histologic, immunophenotypic, cytogenetic and molecular data. We review the diagnostic criteria including clinical, immunophenotypic and molecular characteristics of patients with HCL-V and other HCL-like disorders including HCL, SDRPL, SMZL, B-PLL and the Japanese form of HCL. We also discuss the different criteria allowing us to separate these different entities and we will update the recent therapeutic options that have emerged, in particular the advances with chemoimmunotherapy and/or targeted therapies.

DNA Methylation-Based Classification of Hairy Cell Leukemia and Splenic B Cell Lymphoma

Improved classification of rare lymphoid neoplasms would be aided by a deeper understanding of their underlying molecular features and is important for diagnosis, prognosis and therapy. Tumor entities classified within the WHO category of splenic B cell lymphomas and leukemias often exhibit heterogenous, transecting features, and include hairy cell leukemia (HCL), splenic diffuse red pulp lymphoma (SDRPL), splenic marginal zone lymphoma (SMZL), and the newly described WHO entity, splenic B cell lymphoma/leukemia with prominent nucleoli (SBLPN); the latter including patients formerly classified as HCL-variant (HCL-V). Genome-wide epigenetic information provides a tumor cell fingerprint combining cell-of-origin and tumor-specific events. Here we used DNA methylation to perform an unbiased molecular subclassification and to explore novel biological aspects of these patients. Samples from patients with a pathological diagnosis of HCL, HCL-V, SDRPL and SMZL (made prior to the 5 th WHO revision and ICC classifications) were obtained from 19 institutions across 9 countries, totaling 367 patients. Cells were FACS-purified where necessary and DNA was analyzed by 450/850K Illumina DNA methylation arrays. Genetic mutations were assessed by whole-exome or targeted sequencing, IGHV-D-J sequences by Sanger sequencing, and copy number alterations (CNAs) by Illumina arrays. The 1000 most variable CpG methylation sites were used for k-means clustering. Recursive feature elimination/random forest algorithms were used to develop a classifier for DNA methylation-based subgroups with 98% accuracy. Unsupervised clustering of 197 patients diagnosed with HCL, HCL-V or SDRPL revealed 5 distinct DNA methylation (M) subgroups ( Figure 1). Subgroup assignment was stable throughout longitudinal sampling (including pre/post-treatment) and consistent between splenic, bone marrow and PBMC derived cells. A subgroup with universally clonal BRAF-V600E mutations and majority diagnosed as HCL was termed the M-HCL subgroup ( Table 1). Four other groups termed M-SBLPN1-4 contained all HCL-V and SDRPL diagnosed samples and were devoid of BRAF-V600E mutations. M-SBLPN1 comprised MAP2K1 mutations (91%) and was enriched for CREBBP, ARIDIA and TERT-promoter mutations. These patients displayed an HCL-like immunophenotype (64.3% CD25+) with 1/3 diagnosed as HCL. M-SBLPN2 exhibited the highest prevalence of TP53 mutations and concomitant genomic instability. Patients in M-SBLPN1,2 were enriched in unmutated IGHV4-34 rearrangements. M-SBLPN3,4 subgroups displayed an immunophenotype more dissimilar to HCL, mutated IGHV genes, and enrichment of IGLL5, SYK and BIRC3 mutations. M-SBLPN4 contained the most SDRPL samples, suggesting it may represent the SDRPL entity retained by the WHO. We next uncovered that 29/170 SMZL patients displayed DNA methylation patterns mapping to M-SBLPN2-4. These patients were phenotypically and molecularly similar to SBLPN (70% displaying villous morphology and depleted in IGHV1-2*04, NOTCH2, KLF2 mutations), likely representing SMZL patients suggested for reassignment to SBLPN in the updated WHO classification. To elucidate molecular pathways governing the biology of M-SBLPN subgroups, transcription factor motif enrichment analysis in hypomethylated genomic regions revealed selective activation of AP-1 in M-HCL along with ETS in M-SBLPN1,2. Both transcription factors are downstream of MAPK signaling, consistent with activating BRAF and MAP2K1 mutations in these subgroups. However, we observed strong ETS enrichment in the absence of MAP2K1 in M-SBLPN along with mutual exclusivity of MAP2K1 and TP53 mutations, suggesting TP53 mutations are driving ETS activation. Although lymphoid neoplasms rarely exhibit TERT promoter mutations, 83% of M-SBLPN1 patients showed the c.-124C>T mutation commonly observed in other cancers producing an ETS binding site and ectopic TERT activation. ETS activation and gain of an ETS site by mutation implies oncogenesis involves aberrant TERT activation in this subgroup. In summary, we have developed a DNA methylation-based classifier that resolves 4 SBLPN subgroups with distinct molecular features, and reclassifies a subset of SMZL and HCL patients, adding further information to the updated WHO/ICC entities. We reveal distinct biological pathways operating in M-SBLPN subgroups that may aid targeted therapy approaches.

Monoclonal B-cell lymphocytosis with a non-CLL immunophenotype - Review of 34 cases.

The monoclonal B-cell lymphocytosis (MBL) introduced as new entities in the 2008 WHO classification, are defined by circulating B-cell clone <5.109/L without organomegaly and previous and/or simultaneous lymphoproliferative disorders. The MBL were subclassified in MBL CLL type (the most frequent), MBL atypical CLL type and MBL non-CLL type (rarely reported in literature). Here the clinic, cytologic, immunologic and genetic features of MBL non-CLL type were described from a series of 34 cases. As previously reported, present cases presented immunologic and genetic similarities to MZL and could be associated to the new proposed entity CBL-MZ (clonal B-cell lymphocytosis of marginal zone origin). In addition, few cases presented similarities to splenic diffuse red pulp lymphoma (SDRPL). In conclusion, according to the literature, MBL with non-CLL type (assimilated to CBL-MZ) may be a premalignant state of MZL and/or SDRPL.

Novel targeted treatments in hairy cell leukemia and other hairy cell-like disorders.

In the category of mature B-cell neoplasms, splenic B-cell lymphoma and leukemia were clearly identified and include four distinct entities: hairy cell leukemia (HCL), splenic marginal zone lymphoma (SMZL), splenic diffuse red pulp lymphoma (SDRPL) and the new entity named splenic B-cell lymphoma/leukemia with prominent nucleoli (SBLPN). The BRAFV600E mutation is detected in nearly all HCL cases and offers a possibility of targeted therapy. BRAF inhibitors (BRAFi) represent effective and promising therapeutic approaches in patients with relapsed/refractory HCL. Vemurafenib and dabrafenib were assessed in clinical trials. The BRAFV600E mutation is missing in SDRPL and SBLPN: mitogen-activated protein kinase 1 (MAP2K1) mutations were found in 40% of SBLPN and VH4-34+ HCL patients, making possible to use MEK inhibitors (MEKi) such as trametinib, cobimetinib or binimetinib in monotherapy or associated with BRAFi. Other mutations may be associated and other signaling pathways involved, including the B-cell receptor signaling (BCR), cell cycle, epigenetic regulation and/or chromatin remodeling. In SDRPL, cyclin D3 (CCND3) mutations were found in 24% of patients, offering the possibility of using cell cycle inhibitors. Even if new emerging drugs, particularly those involved in the epigenetic regulation, have recently been added to the therapeutic armamentarium in HCL and HCL-like disorders, purine nucleoside analogs more and more associated with anti-CD20 monoclonal antibodies, are still used in the frontline setting. Thanks to the recent discoveries in genetics and signaling pathways in HCL and HCL-like disorders, new targeted therapies have been developed, have proven their efficacy and safety in several clinical trials and become essential in real life: BRAFi, MEKi, Bruton Tyrosine Kinase inhibitors (BTKi) and anti-CD22 immunotoxins. New other drugs emerged and have to be assessed in the future. In this article, we will discuss the main mutations identified in HCL and HCL-like disorders and the signaling pathways potentially involved in the pathogenesis of the different hairy cell disorders. We will discuss the results of the recent clinical trials, which will help us to propose an algorithm useful in clinical practice and we will highlight the different new drugs that may be used in the near future.

The Role of Splenectomy in Management of Splenic B-Cell Lymphomas

Introduction: Splenic B-cell lymphomas are rare and understudied entities. Over the past decade, outcomes of splenectomy for patients with splenic marginal zone lymphoma (SMZL), hairy cell leukemia variant (HCLv), and splenic diffuse red pulp lymphoma (SDRPL) have not been studied in the United States outside of the SEER database. Splenectomy is still required for a definitive pathological diagnosis in many patients with splenic lymphomas other than classical hairy cell leukemia (cHCL). In addition, splenectomy can be effective therapy with durable responses. Our study aimed to investigate the diagnostic and therapeutic role of splenectomy for indolent splenic B-cell lymphomas other than cHCL. Methods: All patients who underwent splenectomy between 1 August 2011 and 1 August 2021 (n=87) were identified using pathology records and the Wilmot Cancer Institute (WCI) lymphoma database at the University of Rochester Medical Center (URMC). All patients in the database with a clinical diagnosis of non-cHCL splenic B-cell lymphoma who did not undergo splenectomy (n=20) were identified to obtain a comparison cohort. Information abstracted from the medical records included the sociodemographic data, date of diagnosis, treatments utilized, and complications of splenectomy. Follow up continued until the last documentation of medical intervention available. Results: Forty-nine patients (median age 68 years; IQR: 64-75) who underwent splenectomy had a splenic B-cell lymphoma other than cHCL (SMZL n=33, HCLv n=9, SDRPL n=7). Median follow up was 3.9 years and median overall survival (OS) was 5.4 years (95% CI: 4.0, not estimated) (Figure 1A). Splenectomy was tolerable except for 1 patient who had fatal post-operative complications. Patient post-operative hospital discharge was within 4 days for 61.2% (95% CI: 46.0%, 73.4%) and within 10 days for 93.9%, (95% CI 80.8%, 98.2%) (Figure 1B). Splenectomy alone was first line therapy for 25 patients. Splenectomy resulted in a change in lymphoma diagnosis in 5 (26.3%) of the 19 patients who underwent splenectomy after initial medical therapy. To compare the outcomes of first line management with splenectomy versus medical therapy, we identified all patients with a presumed diagnosis of a splenic B-cell lymphoma other than cHCL who never had a splenectomy (n=20). Of these patients, 11 remained on observation and 9 required medical treatment. The five patients who had first line splenectomy followed by rituximab therapy as initial therapy were excluded from this comparison. Subsequent treatment for progressive lymphoma was required in 3 (33%) patients initially treated medically compared to 4 (16%) patients undergoing initial splenectomy. Of the 7 patients diagnosed with SDRPL by splenectomy, 5 remained in complete remission after surgery. Conclusion: Splenectomy is an important method for the diagnosis and treatment of splenic B-cell lymphomas with comparable risk/benefit profile to medical therapy and the potential for durable remission. Splenectomy resulted in a change in lymphoma diagnosis in 26% patients after failure of initial medical treatment. Our data suggests that patients with splenic lymphomas other than cHCL should be considered for diagnostic and therapeutic splenectomy at a high surgical volume center with experience in performing splenectomies. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Deciphering Genetic Alterations of Hairy Cell Leukemia and Hairy Cell Leukemia-like Disorders in 98 Patients.

Simple SummaryThe diagnosis of hairy cell leukemia (cHCL) and HCL-like disorders, including the variant form of HCL (vHCL) and splenic diffuse red pulp lymphoma (SDRPL) can be challenging, particularly in complex situations. The integration of all data, including molecular data, is essential for distinguishing the different entities. The BRAFV600E mutation is identified in most cHCL cases, whereas it is absent in vHCL and SDRPL. MAP2K1 mutations are observed in half of vHCL cases and in cHCL BRAFWT and they are associated with a worse prognosis. The interest in deep sequencing for the diagnosis and prognosis of hairy cell leukemia and HCL-like disorders is essential. Some KLF2 genetic alterations have been localized on the AID consensus motif, suggesting an AID-induced mutation mechanism. KLF2 is the second most altered gene in HCL, and mutations must be investigated to confirm whether AID could be responsible for the genetic alterations in this gene. Clonal evolution can be observed in half of the cases.Hairy cell leukemia (cHCL) patients have, in most cases, a specific clinical and biological presentation with splenomegaly, anemia, leukopenia, neutropenia, monocytopenia and/or thrombocytopenia, identification of hairy cells that express CD103, CD123, CD25, CD11c and identification of the V600E mutation in the B-Raf proto-oncogene (BRAF) in 90% of cases. Monocytopenia is absent in vHCL and SDRPL patients and the abnormal cells do not express CD25 or CD123 and do not present the BRAFV600E mutation. Ten percent of cHCL patients are BRAFWT and the distinction between cHCL and HCL-like disorders including the variant form of HCL (vHCL) and splenic diffuse red pulp lymphoma (SDRPL) can be challenging. We performed deep sequencing in a large cohort of 84 cHCL and 16 HCL-like disorders to improve insights into the pathogenesis of the diseases. BRAF mutations were detected in 76/82 patients of cHCL (93%) and additional mutations were identified in Krüppel-like Factor 2 (KLF2) in 19 patients (23%) or CDKN1B in 6 patients (7.5%). Some KLF2 genetic alterations were localized on the cytidine deaminase (AID) consensus motif, suggesting AID-induced mutations. When analyzing sequential samples, a clonal evolution was identified in half of the cHCL patients (6/12 pts). Among the 16 patients with HCL-like disorders, we observed an enrichment of MAP2K1 mutations in vHCL/SDRPL (3/5 pts) and genes involved in the epigenetic regulation (KDM6A, EZH2, CREBBP, ARID1A) (3/5 pts). Furthermore, MAP2K1 mutations were associated with a bad prognosis and a shorter time to next treatment (TTNT) and progression-free survival (PFS), independently of the HCL classification.

Immunophenotypic Analysis of Hairy Cell Leukemia (HCL) and Hairy Cell Leukemia-like (HCL-like) Disorders.

Simple SummaryHairy cell leukemia (HCL) is a rare B cell neoplasm that accounts for 2% of B-cell lymphomas. The diagnosis was based on the presence of abnormal lymphoid cells that expressed CD103, CD123, CD25 and CD11c. The aim of this retrospective study was to describe the immunophenotypic profile of HCL and HCL-like disorders using 13 markers and to assess the added value of immunophenotypic row data and unsupervised analysis. We confirmed that the immunological profile alone is not sufficient and that morphologic, phenotypic and molecular data need to be integrated.Hairy cell leukemia (HCL) is characterized by abnormal villous lymphoid cells that express CD103, CD123, CD25 and CD11c. HCL-like disorders, including hairy cell leukemia variant (vHCL) and splenic diffuse red pulp lymphoma (SDRPL), have similar morphologic criteria and a distinct phenotypic and genetic profile. We investigated the immunophenotypic features of a large cohort of 82 patients: 68 classical HCL, 5 vHCL/SDRPL and 9 HCL-like NOS. The HCL immunophenotype was heterogeneous: positive CD5 expression in 7/68 (10%), CD10 in 12/68 (18%), CD38 in 24/67 (36%), CD23 in 22/68 (32%) and CD43 in 19/65 (31%) patients. CD26 was expressed in 35/36 (97%) of HCL patients, none of vHCL/SDRPL and one of seven HCL-like NOS (14%). When adding CD26 to the immunologic HCL scoring system (one point for CD103, CD123, CD25, CD11c and CD26), the specificity was improved, increasing from 78.6% to 100%. We used unsupervised analysis of flow cytometry raw data (median fluorescence, percentage of expression) and the mutational profile of BRAF, MAP2K1 and KLF2. The analysis showed good separation between HCL and vHCL/SDRPL. The HCL score is not sufficient, and the use of unsupervised analysis could be promising to achieve a distinction between HCL and HCL-like disorders. However, these preliminary results have to be confirmed in a further study with a higher number of patients.

The Genomics of Hairy Cell Leukaemia and Splenic Diffuse Red Pulp Lymphoma.

Simple SummaryHairy cell leukaemia is a rare chronic lymphoid malignancy with distinctive clinical and laboratory features which include an enlarged spleen, low blood counts, and infiltration of the spleen and bone marrow, with lymphocytes that have a villous or hairy cytoplasmic border. Historically it has been responsive to a range of treatment modalities including splenectomy, alpha interferon, and more recently chemotherapy, but none are curative. This review describes the chromosome abnormalities, genomic mutations, DNA methylation patterns, and immunoglobulin gene usage in this disease. We then discuss how the discovery of a specific mutation in a single gene (BRAF), present in almost all cases but not in hairy cell variant or splenic lymphoma with villous lymphocytes, two other splenic lymphomas with similar features, has provided new insights into its biology, a new diagnostic test, and a new therapeutic target.Classical hairy cell leukaemia (HCLc), its variant form (HCLv), and splenic diffuse red pulp lymphoma (SDRPL) constitute a subset of relatively indolent B cell tumours, with low incidence rates of high-grade transformations, which primarily involve the spleen and bone marrow and are usually associated with circulating tumour cells characterised by villous or irregular cytoplasmic borders. The primary aim of this review is to summarise their cytogenetic, genomic, immunogenetic, and epigenetic features, with a particular focus on the clonal BRAFV600E mutation, present in most cases currently diagnosed with HCLc. We then reflect on their cell of origin and pathogenesis as well as present the clinical implications of improved biological understanding, extending from diagnosis to prognosis assessment and therapy response.

Updates in hairy cell leukemia (HCL) and variant-type HCL (HCL-V): rationale for targeted treatments with a focus on ibrutinib.

Hairy cell leukemia (HCL) and HCL-like disorders such as hairy cell leukemia variant (HCL-V) and splenic diffuse red pulp lymphoma (SDRPL) are rare indolent B-cell malignancies. Purine analogs (PNAs), alone or in association with rituximab (R), are the standard of care for HCL in the first-line setting. However, PNAs are toxic and patients may become resistant to these drugs. Therefore, new therapeutic strategies are needed. Several recent in vitro studies highlighted the importance of the interactions between HCL cells and their microenvironment, in particular with bone marrow stromal cells, endothelial cells, and the extracellular matrix. In these interactions, chemokine receptors and adhesion molecules play a major role. Moreover, the importance of signaling pathways, like BRAF, BCR, and CXCR4 has been underlined. Bruton’s tyrosine kinase (BTK) is a fundamental signal transmitter of BCR and CXCR4 in HCL. Preclinical and recent clinical data showed an efficacy of ibrutinib, a BTK inhibitor (BTKi), in HCL and HCL-V. These promising results joined those of other emerging drugs like BRAF or MEK inhibitors and anti-CD22 immunotoxins.Plain Language Summary Bruton’s tyrosine kinase (BTK) inhibitors (BTKi) in hairy cell leukemia (HCL) and variant-type HCL The treatment of hairy cell leukemia (HCL) has changed significantly in recent years. In the first-line settings, treatment with purine analogs (PNAs) with or without anti-CD20 monoclonal antibodies remains the gold standard in 2022. In relapsed/refractory HCL, other drugs are needed: BRAF inhibitors: vemurafenib monotherapy with or without rituximab or dabrafenib in combination with trametinib, an MEK inhibitor (MEKi), as well as the anti-CD22 antibody drug conjugate moxetumomab pasudotox.There are arguments for the use of Bruton’s tyrosine kinase inhibitors (BTKi). Ibrutinib was recently tested in a multisite phase 2 study in 37 patients with either HCL (28 patients: 76%) or HCL-V (nine patients: 24%) including two who were previously untreated. Patients received single-agent ibrutinib at 420 mg daily (24 patients) or 840 mg daily (13 patients) until disease progression or unacceptable toxicity. The overall response rate (ORR) at 32 weeks was 24%, increasing to 36% at 48 weeks and reaching 54% at any time since starting ibrutinib. Seven patients achieved a complete response (CR) as the best response at any time on study, while 13 patients had a partial response (PR) and 10 patients had stable disease (SD). Interestingly, the response rate was not statistically different between HCL and HCL-V patients, suggesting that ibrutinib could be an option in both entities. The estimated 36-month progression-free survival (PFS) was 73% and the estimated 36-month overall survival (OS) was 85%, with no differences between HCL and HCL-V. The frequency of cardiovascular grade 1–2 adverse events (AEs) was 16% for atrial fibrillation; 3% for atrial flutter; 32% for hypertension; and 0%, 3%, and 11%, respectively, for grade ⩾ 3 AEs. Unlike in chronic lymphocytic leukemia (CLL), where the mechanism of action of ibrutinib is well known, the mechanism of action of ibrutinib in HCL appears to be unclear. No mutations were identified in patients with progressive disease, suggesting that the mechanisms of resistance could be different between HCL and CLL. The BTKi that are not yet approved are challenged by the new other targeted treatments.

Hairy cell leukemia 2022: Update on diagnosis, risk-stratification, and treatment.

Hairy cell leukemia (HCL) and HCL-like disorders, including HCL variant (HCL-V) and splenic diffuse red pulp lymphoma (SDRPL), are a very heterogeneous group of mature lymphoid B-cell disorders characterized by the identification of hairy cells, a specific genetic profile, a different clinical course, and the need for appropriate treatment. Diagnosis of HCL is based on morphological evidence of hairy cells, an HCL immunologic score of 3 or 4 based on the CD11C, CD103, CD123, and CD25 expression, the trephine biopsy which makes it possible to specify the degree of tumoral medullary infiltration and the presence of BRAFV600E somatic mutation. Progression of patients with HCL is based on a large splenomegaly, leukocytosis, a high number of hairy cells in the peripheral blood, and the immunoglobulin heavy chain variable region gene mutational status. VH4-34-positive HCL cases are associated with a poor prognosis. Patients should be treated only if HCL is symptomatic. Chemotherapy with risk adapted therapy purine analogs (PNAs) are indicated in first-line HCL patients. The use of chemo-immunotherapy combining PNAs and rituximab (R) represents an increasingly used therapeutic approach. Management of relapsed/refractory disease is based on the use of BRAF inhibitors (BRAFi) plus rituximab or MEK inhibitors (MEKi), recombinant immunoconjugates targeting CD22 or Bruton Tyrosine Kinase inhibitors (BTKi). However, the optimal sequence of the different treatments remains to be determined. The Bcl2-inhibitors (Bcl-2i) can play a major role in the future.

Epidemiology of Hairy Cell Leukemia (HCL) and HCL-Like Disorders

Hairy cell leukemia (HCL) is a very rare and well-defined entity that is characterized by the presence of hairy cells expressing the characteristic markers CD11c, CD25, CD103 and CD123 and in most cases by the presence of the BRAFV600E mutation. The incidence rate, directly adjusted to the 2000 United States standard population is estimated at 0.62 per 100 000 person-years (PA) in white men, 0.21 in black men, 0.20 in Asian men and 0.06 American Indian or Alaska native men. Based on the estimated 2019 leukemia incidence, of 61,780 in the United States, approximately 1,240 new HCL cases are expected per year, with only 60–75 new patients having a variant form of HCL each year. In France, the median age of patients at diagnosis is 63 years in men and 59 years in women. There is a strong male predominance, with a sex ratio of 5:1. HCL is a malignant disorder with a good prognosis, with a standardized average survival at 1 year and 5 years of 95% (95% CI: 91-97 for both). The etiology of HCL remains unknown. The risk of secondary cancers is high, especially that of another malignant hematologic disorder. This high risk justifies the need for prolonged hematological monitoring. HCL must be distinguished from other HCL-like disorders, including the variant form of HCL (HCL-V) or splenic diffuse red pulp lymphoma (SDRPL), warranting the development of international epidemiologic studies.

Hairy cell leukemia: 2020 update on diagnosis, risk stratification, and treatment.

Hairy cell leukemia (HCL) and HCL-like disorders, including HCL variant (HCL-V) and splenic diffuse red pulp lymphoma (SDRPL), are a very heterogeneous group of mature lymphoid B-cell disorders. They are characterized by the identification of hairy cells, a specific genetic profile, a different clinical course and the need for appropriate treatment. Diagnosis of HCL is based on morphological evidence of hairy cells, an HCL immunologic score of three or four based on the CD11C, CD103, CD123, and CD25 expression. Also, the trephine biopsy which makes it possible to specify the degree of tumoral medullary infiltration and the presence of BRAF V600E somatic mutation. Progression of patients with HCL is based on a large splenomegaly, leukocytosis, a high number of hairy cells in the peripheral blood and the immunoglobulin heavy chain variable region gene mutational status. The VH4-34 positive HCL cases are associated with poor prognosis. Risk adapted therapy with purine nucleoside analogs (PNA) are indicated in symptomatic first line HCL patients. The use of PNA followed by rituximab represents an alternative option. Management of progressive or refractory disease is based on the use of BRAF inhibitors associated or not with MEK inhibitors, recombinant immunoconjugates targeting CD22 or BCR inhibitors.

New generation sequencing of targeted genes in the classical and the variant form of hairy cell leukemia highlights mutations in epigenetic regulation genes.

Classical hairy cell leukemia (HCL-c) is a rare lymphoid neoplasm. BRAFV600E mutation, detected in more than 80% of the cases, is described as a driver mutation, but additional genetic abnormalities appear to be necessary for the disease progression. For cases of HCL-c harboring a wild-type BRAF gene, the differential diagnosis of the variant form of HCL (HCL-v) or splenic diffuse red pulp lymphoma (SDRPL) is complex. We selected a panel of 21 relevant genes based on a literature review of whole exome sequencing studies (BRAF, MAP2K1, DUSP2, MAPK15, ARID1A, ARID1B, EZH2, KDM6A, CREBBP, TP53, CDKN1B, XPO1, KLF2, CXCR4, NOTH1, NOTCH2, MYD88, ANXA1, U2AF1, BCOR, and ABCA8). We analyzed 20 HCL-c and 4 HCL-v patients. The analysis of diagnostic samples mutations in BRAF (n = 18), KLF2 (n = 4), MAP2K1 (n = 3), KDM6A (n = 2), CDKN1B (n = 2), ARID1A (n = 2), CREBBP (n = 2) NOTCH1 (n = 1) and ARID1B (n = 1). BRAFV600E was found in 90% (18/20) of HCL-c patients. In HCL-c patients with BRAFV600E, other mutations were found in 33% (6/18) of cases. All 4 HCL-v patients had mutations in epigenetic regulatory genes: KDM6A (n = 2), CREBBP (n = 1) or ARID1A (n = 1). The analysis of sequential samples (at diagnosis and relapse) from 5 patients (2 HCL-c and 3 HCL-v), showed the presence of 2 new subclonal mutations (BCORE1430X and XPO1E571K) in one patient and variations of the mutated allele frequency in 2 other cases. In the HCL-v disease, we described new mutations targeting KDM6A that encode a lysine demethylase protein. This opens new perspectives for personalized medicine for this group of patients.

Toll-like receptor expression and function differ between splenic marginal zone B cell lymphoma and splenic diffuse red pulp B cell lymphoma.

In splenic marginal zone lymphoma (SMZL), specific and functional Toll-like Receptor (TLR) patterns have been recently described, suggesting their involvement in tumoral proliferation. Splenic diffuse red pulp lymphoma with villous lymphocytes (SDRPL) is close to but distinct from SMZL, justifying here the comparison of TLR patterns and functionality in both entities.Distinct TLR profiles were observed in both lymphoma subtypes. SDRPL B cells showed higher expression of TLR7 and to a lesser degree TLR9, in comparison to SMZL B cells. In both entities, TLR7 and TLR9 pathways appeared functional, as shown by IL-6 production upon TLR7 and TLR9 agonists stimulations. Interestingly, circulating SDRPL, but not SMZL B cells, constitutively expressed CD86. In addition, stimulation with both TLR7 and TLR9 agonists significantly increased CD80 expression in circulating SDRPL but not SMZL B cells. Finally, TLR7 and TLR9 stimulations had no impact on proliferation and apoptosis of SMZL or SDRPL B cells.In conclusion, SMZL and SDRPL may derive from different splenic memory B cells with specific immunological features that can be used as diagnosis markers in the peripheral blood.

Hairy cell leukemia 2018: Update on diagnosis, risk-stratification, and treatment.

Disease overviewHairy cell leukemia (HCL) and HCL‐like disorders, including HCL variant (HCL‐V) and splenic diffuse red pulp lymphoma (SDRPL), are a very heterogeneous group of mature lymphoid B‐cell disorders, characterized by the identification of hairy cells, a specific genetic profile, a different clinical course and the need for appropriate treatment.DiagnosisDiagnosis of HCL is based on morphological evidence of hairy cells, an HCL immunologic score of 3 or 4 based on the CD11C, CD103, CD123, and CD25 expression, the trephine biopsy which makes it possible to specify the degree of tumoral medullary infiltration and the presence of BRAF V600E somatic mutation.Risk stratificationProgression of patients with HCL is based on a large splenomegaly, leukocytosis, a high number of hairy cells in the peripheral blood and the immunoglobulin heavy chain variable region gene mutational status. VH4‐34 positive HCL cases are associated with poor prognosisRisk adapted therapyPurine analogs (PNA) are indicated in symptomatic first line HCL patients. The use of PNA followed by rituximab represents an alternative option.Management of progressive or refractory diseaseIt is based on the use of BRAF inhibitors associated or not with MEK inhibitors, recombinant immunoconjugates targeting CD22 or BCR inhibitors.

Exome sequencing identifies recurrent BCOR alterations and the absence of KLF2, TNFAIP3 and MYD88 mutations in splenic diffuse red pulp small B-cell lymphoma.

Splenic diffuse red pulp lymphoma is an indolent small B-cell lymphoma recognized as a provisional entity in the World Health Organization 2008 classification. Its precise relationship to other related splenic B-cell lymphomas with frequent leukemic involvement or other lymphoproliferative disorders remains undetermined. We performed whole-exome sequencing to explore the genetic landscape of ten cases of splenic diffuse red pulp lymphoma using paired tumor and normal samples. A selection of 109 somatic mutations was then evaluated in a cohort including 42 samples of splenic diffuse red pulp lymphoma and compared to those identified in 46 samples of splenic marginal zone lymphoma and eight samples of hairy-cell leukemia. Recurrent mutations or losses in BCOR (the gene encoding the BCL6 corepressor) – frameshift (n=3), nonsense (n=2), splicing site (n=1), and copy number loss (n=4) – were identified in 10/42 samples of splenic diffuse red pulp lymphoma (24%), whereas only one frameshift mutation was identified in 46 cases of splenic marginal zone lymphoma (2%). Inversely, KLF2, TNFAIP3 and MYD88, common mutations in splenic marginal zone lymphoma, were rare (one KLF2 mutant in 42 samples; 2%) or absent (TNFAIP3 and MYD88) in splenic diffuse red pulp lymphoma. These findings define an original genetic profile of splenic diffuse red pulp lymphoma and suggest that the mechanisms of pathogenesis of this lymphoma are distinct from those of splenic marginal zone lymphoma and hairy-cell leukemia.

Mutational Status of Splenic Diffuse Red Pulp Small B-Cell Lymphoma Revealed By Whole Exome Sequencing

Background: Splenic diffuse red pulp lymphoma (SDRPL) is a rare small B cell neoplasm provisionally included in a category of unclassifiable splenic B-cell lymphoma/leukemias in the 2008 WHO classification. SDRPL is characterized by a diffuse pattern of involvement of the splenic red pulp by small monomorphous B lymphocytes. Patients are normally diagnosed at stage IV when spleen, bone marrow and peripheral blood are involved. This indolent but incurable disease is more common in aged males and it shows with splenomegaly and moderate lymphocytosis. The differential diagnosis with other splenic lymphomas such as marginal zone lymphoma, hairy cell lymphoma and its variant is not always easy, due to the similar clinical presentation and the absence of specific molecular markers. Here we studied the mutational status of 15 SDRPL patients using Whole Exome Next Generation Sequencing.Methods: Genomic DNA was extracted from FFPE/FF splenic tumor or bone marrow samples. When available, DNA from oral mucosa was obtained as the corresponding non-tumor control. Whole exome sequencing was performed at CNAG (Barcelona, Spain) following standard protocols for high-throughput paired-end sequencing on the Illumina HiSeq2000 instruments (Illumina Inc., San Diego, CA). Validation of variants was performed by PCR based targeted resequencing using a MiSeq instrument (Illumina Inc., San Diego, CA).We performed paired-end-76pb whole exome sequencing on DNA from 15 SDRPL patients. The corresponding normal counterpart from 3 of the patients was sequenced. From one patient FFPE and bone marrow DNA was available for comparison. In total 9 FFPE tissue samples, 3 FF tissue samples, and 4 bone marrow samples were sequenced. Almost 95% of the selected variants were validated by PCR based resequencing in 9 of the patients, while from 6 of the patients no tissue was available for validation.Results: 290 substitutions and 26 indels were obtained after filtering. Whole exome sequencing permitted us to identify variations in several genes of relevant pathways in lymphomas, such as NFkB pathway (IkBKB, TRAF, TANK, SYK), Apoptosis (BAD, DCPS, BCLAF1), MAPK (CXCR4, TCF3, NF1, MAP3K5), Cell cycle (CCND3, POLD3, BUB1), Chromatin (CREBBP, ARID1A, ARID1B, ARID3A, MLL3), MYC regulators (AKAP10, CTCF, EP400) or WNT signaling (SALL1, WNT5B, GPC6). Moreover, CCND3 and MLL3 were recurrently mutated in 2 different patients. Genes specifically found mutated in other splenic malignancies, such as NOTCH2, BRAF, MAP2K1, and KLF2 were not found mutated in this series of SDRPL patients.Conclusions: SDRPL samples contain somatic mutations involving genes regulating relevant pathways for cell survival, such as NFkB, apoptosis, cell cycle, chromatin, or WNT. The mutational signature of the series studied here may indicate that SDRPL is a distinct entity with specific molecular features different to other lymphoid splenic malignancies. DisclosuresNo relevant conflicts of interest to declare.

Gene Expression Profiling Signatures Allow the Identification of Unclassifiable Leukemic B-Cell Lymphoid Neoplasms

Leukemic B-cell chronic lymphoproliferative disorders (B-CLPD) encompass a heterogeneous group of defined disease entities. However, around 10% of the cases cannot be reliably classified based on the current criteria and are considered B-CLPD not otherwise specified (B-CLPD NOS). Few recurrent mutations and genetic alterations have been reported in some entities, but none is specific.We performed gene expression profiling (GEP) to develop a robust GEP-molecular classifier for leukemic B-CLPD. We analyzed purified blood of 189 B-CLPD, including 54 chronic lymphocytic leukemia (CLL), 54 mantle cell lymphoma (MCL), 12 follicular lymphoma (FL), 23 splenic marginal zone lymphoma (SMZL), 4 splenic diffuse red pulp lymphoma (SDRPL), 4 hairy cell leukemia (HCL), 4 HCL-variant (HCL-v), 6 lymphoplasmacytic lymphoma (LPL) and 28 B-CLPD NOS. We used a multiple step approach to build a GEP-array classifier and then analyzed an additional series as a validation cohort by quantitative PCR (qPCR). Mutational analysis of BRAF, MAP2K1, MYD88, NOTCH1, NOTCH2, SF3B1 and TP53 and copy number alterations were studied.In the training set, a supervised analysis clustering revealed that each B-CLPD entity has a specific expression profile. By a multi-step GEP classifier using 43 genes (Table 1) we could classify CLL, SOX11-positive MCL (MCLc), HCL, FL, SOX11-negative MCL (MCLi) and HCL-v cases in six successive stages. However, we were not able to clearly identify distinct signatures for LPL, SMZL and SDRPL. Furthermore, we could classify 36% of B-CLPD NOS cases. Interestingly, the 43-gene signature identified in leukemic samples could also classify the 28 tumor splenic biopsies. Finally, we built a simple 8-gene predictive model using qPCR data (including: FMOD, KSR2, SOX11, MYOF, MME, CCND1, CXCR4, and CAMSAP2) that was used in an independent validation cohort and classified 14% B-CLPD NOS cases. The classification yield increased to 61% and 50%, for GEP-array and qPCR, respectively, when additional morphological, molecular and genetic features were considered.Our findings support the use in a routine base of a simple test as a diagnostic tool that can be applied to help multiparameter interpretation in the classification of leukemic B-CLPD and specially B-CLPD NOS.Table 1Gene signatures (43 genes) and steps used for the GEP-array model.Step modelB-CLPDSpecific signatures1CLLFMOD, KSR2, ADTRP, CLNK, LEF1, FILIP1L, CTLA4, IGSF3, EBF12MCLcSOX11, PLEKHG4B, HDGFRP3, CNN3, PON2, SH3BP4, FCGBP, STMN1, FARP1, DBN1, NREP, NINL, MARCKSL1, MEX3D, CRIM1, KAZN3HCLHPGDS, IL1R2, TJP1, PLOD2, EMP1, NOVA14FLMME, SLC2A5, SMAD1, PRDM155MCLiCCND16HCL-vTUSC1, LRP1B, KCNJ3, NRCAM, MS4A14, FAM129C,CXCR47MiscellaneousLPL-SDRPL-SMZLNo specific genes CLLchronic lymphocytic leukemia; FL: follicular lymphoma, HCL: hairy cell leukemia;HCL-v: hairy cell leukemia variant; LPL, lymphoplasmacytic lymphoma; MCLc: conventionalSOX11-positive mantle cell lymphoma; MCLi: indolent SOX11-negative mantle cell lymphoma;SDRPL, splenic diffuse red pulp lymphoma; SMZL, splenic marginal zone lymphoma.Bold letters indicate some of the genes included in the simple qPCR model. DisclosuresLopez-Guillermo:Roche, Celgene, Mundipharma, Gilead, Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding.

The experience of diagnostic and treating splenic diffuse red pulp lymphoma

The experience of diagnostic and treating splenic diffuse red pulp lymphoma