Clinical and molecular characteristics of lymphoplasmacytic lymphoma not associated with an IgM monoclonal protein: A multicentric study of the Rete Ematologica Lombarda (REL) network

Fifth Edition of the World Health Classification of Tumors of the Hematopoietic and Lymphoid Tissues: B-cell Neoplasms

We review B-cell neoplasms in the 5th edition of the World Health Organization classification of hematolymphoid tumors (WHO-HEM5). The revised classification is based on a multidisciplinary approach including input from pathologists, clinicians, and other experts. The WHO-HEM5 follows a hierarchical structure allowing the use of family (class)-level definitions when defining diagnostic criteria are partially met or a complete investigational workup is not possible. Disease types and subtypes have expanded compared with the WHO revised 4th edition (WHO-HEM4R), mainly because of the expansion in genomic knowledge of these diseases. In this review, we focus on highlighting changes and updates in the classification of B-cell lymphomas, providing a comparison with WHO-HEM4R, and offering guidance on how the new classification can be applied to the diagnosis of B-cell lymphomas in routine practice.

Lymphoplasmacytic lymphoma relapse presenting as isolated multifocal subcutaneous adipose tissue infiltrates on 18F-FDG PET/CT

Lymphoplasmacytic lymphoma (LPL)/Waldenström macroglobulinemia (WM) is an uncommon mature B cell lymphoma usually involving the bone marrow and, less commonly, the spleen and/or lymph nodes. This case presents a pathology-confirmed isolated extramedullary relapse of LPL, located in subcutaneous adipose tissue, 5 years after successful treatment of WM.

[Classification of indolent B-cell lymphomas : Novelties and open questions]

The 5th edition of the WHO classification (WHO-HAEM5) and the International Consensus Classification (ICC) have considerable overlap but also some distinct differences in categorizing indolent B‑cell lymphomas. Most differences with the expected impact on the daily diagnostic routine relate to follicular lymphoma (FL). Grading of FL remains mandatory only in the ICC; a diffuse growth pattern in an FL with > 15 blasts per high-power field (FL grade 3A) is not automatically classified as DLBCL according to WHO-HAEM5, and an FL subtype with unusual morphology (blastoid or large centrocyte) and biology is recognized as an entity only in the WHO-HAEM5. With the exception of B‑prolymphocytic leukemia, which is no longer acknowledged in WHO-HAEM5, there are only minor differences between both classifications and include updated names of entities, improved diagnostic criteria, and upgrades from provisional to definite entities.

Diagnostic, Prognostic, and Predictive Role of Next-Generation Sequencing in Mature Lymphoid Neoplasms

Lymphoma is a clinically and biologically heterogeneous disease. Next-generation sequencing (NGS) has expanded our understanding of this heterogeneity at the genetic level, refining disease classification, defining new entities, and providing additional information that can be used in diagnosis and management. This review highlights some of the NGS findings in lymphoma and how they can be used as genetic biomarkers to aid diagnosis and prognosis and guide therapy.

Report of Consensus Panel 3 from the 11th International workshop on Waldenström's Macroglobulinemia: Recommendations for molecular diagnosis in Waldenström's Macroglobulinemia

Apart from the MYD88L265P mutation, extensive information exists on the molecular mechanisms in Waldenström's Macroglobulinemia and its potential utility in the diagnosis and treatment tailoring. However, no consensus recommendations are yet available. Consensus Panel 3 (CP3) of the 11th International Workshop on Waldenström's Macroglobulinemia (IWWM-11) was tasked with reviewing the current molecular necessities and best way to access the minimum data required for a correct diagnosis and monitoring. Key recommendations from IWWM-11 CP3 included: (1) molecular studies are warranted for patients in whom therapy is going to be started; such studies should also be done in those whose bone marrow (BM) material is sampled based on clinical issues; (2) molecular studies considered essential for these situations are those that clarify the status of 6q and 17p chromosomes, and MYD88, CXCR4, and TP53 genes. These tests in other situations, and/or other tests, are considered optional; (3) independently of the use of more sensitive and/or specific techniques, the minimum requirements are allele specific polymerase chain reaction for MYD88L265P and CXCR4S338X using whole BM, and fluorescence in situ hybridization for 6q and 17p and sequencing for CXCR4 and TP53 using CD19+ enriched BM; (4) these requirements refer to all patients; therefore, sample should be sent to specialized centers.

Lymphoplasmacytic lymphoma with IgG or IgA paraprotein: a study of 29 cases including cases that can mimic plasma cell neoplasms

Lymphoplasmacytic lymphoma (LPL) with IgG or IgA paraprotein is rare and a subset of cases can mimic a plasma cell neoplasm (PCN). We studied 29 such cases to explore their clinicopathological features and the best diagnostic approaches with a focus on bone marrow findings. The cohort included 18 men and 11 women with a median age of 68 years. The median M protein was 3.1 g/dL, IgG in 19 patients (66%), IgA in 9 (31%), and dual IgG/IgA in 1 (3%). All patients had bone marrow involvement with CD138+ plasma cells (PCs) ranging from 1 to 35% (median, 10%). Two patients also had amyloidosis. Immunoglobulin light chain concordant monotypic PCs and monotypic B cells were identified in 96% of cases assessed by flow cytometry. Notably, the neoplastic PCs were consistently positive for CD45 (dim, 100%), CD19 (96%), CD81 (89%), CD27 (83%), rarely and only weakly or partially express CD56 (16%), whereas CD117 was consistently negative. Eleven cases analyzed by fluorescence in situ hybridization were negative for CCND1::IGH and myeloma-related aberrations. MYD88 mutation was detected in 17 of 24 cases (71%), and CXCR4 mutation was identified in 6 of 19 cases (32%), of which 4 had concurrent MYD88 mutation. In conclusion, the results highlight a potential diagnostic pitfall of LPL associated with marked plasmacytic differentiation and an IgG or IgA paraprotein that can resemble a PCN. Useful features in favor of LPL against PCN include the characteristic immunophenotypic profile of the PCs in LPL, absence of CCND1::IGH, and the presence of MYD88 and/or CXCR4 mutations.

The 5th edition of the World Health Organization Classification of Haematolymphoid Tumours: Lymphoid Neoplasms

We herein present an overview of the upcoming 5^th edition of the World Health Organization Classification of Haematolymphoid Tumours focussing on lymphoid neoplasms. Myeloid and histiocytic neoplasms will be presented in a separate accompanying article. Besides listing the entities of the classification, we highlight and explain changes from the revised 4^th edition. These include reorganization of entities by a hierarchical system as is adopted throughout the 5^th edition of the WHO classification of tumours of all organ systems, modification of nomenclature for some entities, revision of diagnostic criteria or subtypes, deletion of certain entities, and introduction of new entities, as well as inclusion of tumour-like lesions, mesenchymal lesions specific to lymph node and spleen, and germline predisposition syndromes associated with the lymphoid neoplasms.

[Clinical and biological characteristics of non-IgM lymphoplasmacytic lymphoma]

Objective: The study aims to explore the clinical and biological characteristics of patients with non-IgM lymphoplasmacytic lymphoma (LPL) . Methods: The clinical data of 340 patients with LPL admitted to the Institute of Hematology & Blood Diseases Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College were collected retrospectively, including 23 cases of the non-IgM LPL and 317 cases of the Waldenström's macroglobulinemia (WM) , from July 1993 to August 2020. The clinical and biological characteristics of the two groups were compared. Results: Among 23 patients with the non-IgM type LPL, two patients secreted monoclonal IgA, 14 patients secreted monoclonal IgG, and seven patients did not secrete monoclonal immunoglobulin. The median age of the non-IgM LPL and WM were both 62 (35-81) years old. Compared with the WM group, the proportion of women (56.5% vs 27.3%, P=0.007) , the proportion of splenomegaly (60.1% vs 43.8%, P=0.100) , and the proportion of extranodal invasion (21.7% vs 12.3%, P=0.672) in non-IgM LPL group were higher. Eighteen patients were tested for MYD88 gene mutation, and the overall mutation rate of MYD88 was 55.6%. In the non-IgM LPL group, a total of 17 patients received treatment, which had a comparable proportion (94.4% vs 92.7%, P=0.488) to the WM group. Sixteen patients were evaluated for efficacy, and the overall remission rate of the first-line treatment was 87.5%. The median follow-up time was 33.9 (3.5-125.1) months, and the median PFS and OS were both not reached. The 3-year PFS and OS rates were 71.4% and 68.9%, respectively. In the WM group, the median PFS was 66.2 months and the median OS was 78.1 months. Compared with the WM group, in the non-IgM group no significant differences in PFS (P=0.340) and OS (P=0.544) were seen. Conclusion: The clinical and biological characteristics of the non-IgM LPL and WM patients were similar. However, the proportion of women and extranodal involvement were higher in the non-IgM LPL group. The survival and prognosis of the non-IgM LPL patients were similar to those of the WM patients.

External-Beam Radiotherapy Alone Management of Primary CNS Lymphoplasmacytic Lymphoma: A Vietnamese Case Report and Literature Review

Background

Primary central nervous system (CNS) lymphoma is an uncommon non-Hodgkin disease limited to the CNS, and most cases are diffuse large B-cell lymphomas. Other pathologies, including lymphoplasmacytic lymphoma (LPL), are exceedingly rare and poorly understood. The clinical presentation of primary CNS LPL is diverse. It depends on the original site and the tumor’s extension. There is currently no consensus on a treatment strategy for this uncommon manifestation. To our knowledge, no previously published case was successfully treated with radiation therapy alone.

Case Presentation

We present here a case of primary CNS LPL. A 46-year-old, previously healthy woman was presented with a worsening headache and lower extremity numbness. Multifocal enhanced masses were detected in an MRI with biopsy results consistent with LPL. A complete staging workup was performed with no evidence of systemic disease. The patient received external-beam radiotherapy alone and had a complete remission. After 2 years of follow-up, she remains disease-free.

Conclusion

Radiation alone is a promising treatment option for primary CNS lymphoplasmacytic lymphoma.

Waldenström's Macroglobulinemia: An Exploration into the Pathology and Diagnosis of a Complex B-Cell Malignancy

After 77 years since the initial description, Waldenström macroglobulinemia (WM) remains as a bone marrow neoplastic disorder with lymphoplasmacytic differentiation oversecreting a monoclonal immunoglobulin M (IgM). However, many biological and genetic aspects of this entity have been unraveled and it is now easy to correctly diagnose patients with this illness. The diagnosis requires the presence of a monoclonal IgM component and bone marrow lymphoid infiltration must be demonstrated. In addition, other small B-cell lymphoid neoplasms with plasma cell differentiation must be discarded. Although the clinical picture is highly heterogeneous, the diagnosis is much easier today compared to the past, since now we can demonstrate the presence of somatic mutations, especially the L265P mutation in the MYD88 gene, highly characteristic of WM (>90% of the patients), followed by the WHIM-like mutations in the CXCR4 gene (~35%). The identification of these mutations is very important, because they can modulate the response to new treatments with Bruton's tyrosine kinase (BTK) inhibitors. Thus, the conventional prognostic factors that predict the outcome of these patients (anemia, thrombopenia, high M component, high B2M, and advanced age), must be complemented with the genetic evaluation of the patient, that can help us in the prediction of the risk of transformation from asymptomatic to symptomatic forms (Del6q) and/or from indolent forms of the disease to aggressive lymphomas (CD79b mutations).

How to Sequence Therapies in Waldenström Macroglobulinemia

OPINION STATEMENT

There are multiple treatment options in patients with Waldenström macroglobulinemia, including chemotherapy, monoclonal antibodies, proteasome inhibitors, and covalent Bruton tyrosine kinase (BTK) inhibitors. The choice of therapy should take into account the patient's clinical presentation, comorbidities, and preferences. A thorough discussion should take place to outline the administration, safety, and efficacy of the regimens under consideration. The patient's genomic profile can provide insightful information for the treatment selection. In the frontline and relapsed settings, we favor ibrutinib monotherapy over chemoimmunotherapy or proteasome inhibitor-based regimens in patients with MYD88 and without CXCR4 mutations. For patients with MYD88 and CXCR4 mutations or without MYD88 or CXCR4 mutations, chemoimmunotherapy or proteasome inhibitor-based regimens are favored, but efficacy data with ibrutinib in combination with rituximab and with novel covalent BTK inhibitors are emerging. Autologous stem cell transplant should be considered in special cases in the relapsed setting. Participation in clinical trials is positively encouraged in WM patients in frontline and relapsed settings. Agents of interest include the BCL2 antagonist venetoclax, the CXCR4 inhibitor mavorixafor, and the non-covalent BTK inhibitors pirtobrutinib and ARQ-531.

A matched case-control study comparing features, treatment and outcomes between patients with non-IgM lymphoplasmacytic lymphoma and Waldenström macroglobulinemia

Cases of non-IgM lymphoplasmacytic lymphoma (LPL) are rare. We performed a case-control study comparing features and outcomes of 31 non-IgM LPL cases and 93 Waldenström macroglobulinemia (WM) controls matched by age, sex, and year of diagnosis. Odds of MYD88 mutations were lower (odds ratio (OR) 0.22, p = .05), and median time to treatment was shorter in cases than in controls (4 vs. 32 months; p < .001). Odds of extramedullary disease were higher (OR 4.20, p = .01), while odds of neuropathy (OR 0.22, p = .25), and hyperviscosity (OR 0.26, p = .26) were lower in cases than in controls. Odds of using chemoimmunotherapy were higher (OR 2.62, p = .11) while odds of using proteasome inhibitors (OR 0.35, p = .15) and BTK inhibitors (OR 0.17, p = .21) were lower in cases than in controls. There were no differences in response and overall survival (OS) between cases and controls. Despite clinicopathological differences, response, and survival outcomes are similar between non-IgM LPL cases and WM controls.

MYD88 in the driver's seat of B-cell lymphomagenesis: from molecular mechanisms to clinical implications

More than 50 subtypes of B-cell non-Hodgkin lymphoma (B-NHL) are recognized in the most recent World Health Organization classification of 2016. The current treatment paradigm, however, is largely based on 'one-size-fits-all' immune-chemotherapy. Unfortunately, this therapeutic strategy is inadequate for a significant number of patients. As such, there is an indisputable need for novel, preferably targeted, therapies based on a biologically driven classification and risk stratification. Sequencing studies identified mutations in the MYD88 gene as an important oncogenic driver in B-cell lymphomas. MYD88 mutations constitutively activate NF-κB and its associated signaling pathways, thereby promoting B-cell proliferation and survival. High frequencies of the hotspot MYD88(L265P) mutation are observed in extranodal diffuse large B-cell lymphoma and Waldenström macroglobulinemia, thereby demonstrating this mutation's potential as a disease marker. In addition, the presence of mutant MYD88 predicts survival outcome in B-NHL subtypes and it provides a therapeutic target. Early clinical trials targeting MYD88 have shown encouraging results in relapsed/refractory B-NHL. Patients with these disorders can benefit from analysis for the MYD88 hotspot mutation in liquid biopsies, as a minimally invasive method to demonstrate treatment response or resistance. Given these clear clinical implications and the crucial role of MYD88 in lymphomagenesis, we expect that analysis of this gene will increasingly be used in routine clinical practice, not only as a diagnostic classifier, but also as a prognostic and therapeutic biomarker directing precision medicine. This review focuses on the pivotal mechanistic role of mutated MYD88 and its clinical implications in B-NHL.