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Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is an aggressive myeloid malignancy of the dendritic cell lineage that affects patients of all ages, though the incidence appears to be highest in patients over the age of 60 years. Diagnosis is based on the presence of plasmacytoid dendritic cell precursors expressing CD123, the interleukin-3 (IL-3) receptor alpha, and a distinct histologic appearance. Timely diagnosis remains a challenge, due to lack of disease awareness and overlapping biologic and clinical features with other hematologic malignancies. Prognosis is poor with a median overall survival of 8 to 14 months, irrespective of disease presentation pattern. Historically, the principal treatment was remission induction therapy followed by a stem cell transplant (SCT) in eligible patients. However, bridging to SCT is often not achieved with induction chemotherapy regimens. The discovery that CD123 is universally expressed in BPDCN and is considered to have a pathogenetic role in its development paved the way for the successful introduction of tagraxofusp, a recombinant human IL-3 fused to a truncated diphtheria toxin payload, as an initial treatment for BPDCN. Tagraxofusp was approved in 2018 by the United States Food and Drug Administration for the treatment of patients aged 2 years and older with newly diagnosed and relapsed/refractory BPDCN, and by the European Medicines Agency in 2021 for first-line treatment of adults. The advent of tagraxofusp has opened a new era of precision oncology in the treatment of BPDCN. Herein, we present an overview of BPDCN biology, its diagnosis, and treatment options, illustrated by clinical cases., Competing Interests: Disclosures Naveen Pemmaraju: Pacylex Pharmaceuticals, Astellas Pharma US, ImmunoGen, Inc, Bristol-Myers Squibb Co., Cimeio Therapeutics AG, EUSA Pharma, Menarini Group, Blueprint Medicines, CTI BioPharma, ClearView Healthcare Partners, Novartis Pharmaceutical, Neopharm, Celgene Corporation, AbbVie Pharmaceuticals, Pharma Essentia, Curio Science, DAVA Oncology, Imedex, Intellisphere, CancerNet, Harborside Press, Aptitude Health, Medscape, Magdalen Medical Publishing, OncLive, CareDx, Patient Power, Physician Education Resource (PER): Consultancy/Scientific Advisory Board/Speaking; United States Department of Defense, National Institute of Health/National Cancer Institute (NIH/NCI): Research (Grant); Affymetrix: Research Funding; Dan's House of Hope: Membership on an entity's Board of Directors/Management; ASH Committee on Communications, ASCO Cancer.Net Editorial Board: Leadership; Karger Publishers: Licences; HemOnc Times/Oncology Times: Uncompensated. Eric Deconinck: Stemline Therapeutics: Consultancy, honoraria; ImmunoGen: Consultancy, honoraria; Chugai: Research funding; Novartis: Research funding. Priyanka Mehta: Pfizer, AbbVie, Celgene, Daiichi Sankyo, Jazz Pharmaceuticals, Stemline Therapeutics: Advisory board/honoraria. Irwin Walker: Sanofi: Research funding. Marco Herling: AbbVie, BeiGene, Jazz, Janssen, Stemline Therapeutics, Takeda: Consultancy; Mundipharma EDO, Janpix, Novartis, Roche: Funding of preclinical research. Francine Garnache-Ottou: Stemline Therapeutics, LFB: Consultancy. Nadia Gabarin: Declarations of interest: none. Clinton Campbell: Declarations of interest: none. Johannes Duell: Stemline: Lecturing Yakir Moshe: AbbVie: Advisory board, research funding, speaker; Astellas, Medison: Advisory board, speaker; Gilead, Novartis, Stemline: Advisory board Tariq Mughal: Informa Publishing, Oxford University Press: Royalties. Consultant: Stemline Therapeutics Inc, New York, NY, USA. Mohamad Mohty: Jazz Pharmaceuticals: Research funding, honoraria. Emanuele Angelucci: Menarini/Stemline, Novartis: Honoraria; bluebird bio, Glaxo, Gilead, Roche: Board of Directors or advisory committees; Vifor Pharma, BMS, Vertex Inc.: Participation DMC., (Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.)

The Philadelphia-negative myeloproliferative neoplasms (MPNs) are clonal disorders involving hematopoietic stem and progenitor cells and are associated with myeloproliferation, splenomegaly and constitutional symptoms. Similar signs and symptoms can also be found in patients with chronic inflammatory diseases, and inflammatory processes have been found to play an important role in the pathogenesis and progression of MPNs. Signal transduction pathways involving JAK1, JAK2, STAT3 and STAT5 are causally involved in driving both the malignant cells and the inflammatory process. Moreover, anti-inflammatory and immune-modulating drugs have been used successfully in the treatment of MPNs. However, to date, many unresoved issues remain. These include the role of somatic mutations that are present in addition to JAK2V617F, CALR and MPL W515 mutations, the interdependency of malignant and nonmalignant cells and the means to eradicate MPN-initiating and -maintaining cells. It is imperative for successful therapeutic approaches to define whether the malignant clone or the inflammatory cells or both should be targeted. The present review will cover three aspects of the role of inflammation in MPNs: inflammatory states as important differential diagnoses in cases of suspected MPN (that is, in the absence of a clonal marker), the role of inflammation in MPN pathogenesis and progression and the use of anti-inflammatory drugs for MPNs. The findings emphasize the need to separate the inflammatory processes from the malignancy in order to improve our understanding of the pathogenesis, diagnosis and treatment of patients with Philadelphia-negative MPNs.

Myeloproliferative neoplasms (MPN) are debilitating stem cell-derived clonal myeloid malignancies. Conventional treatments for the BCR-ABL1-negative MPN including polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF) have, so far, been unsatisfactory. Following the discovery of dysregulated JAK-STAT signaling in patients with MPN, many efforts have been directed toward the development of molecularly targeted therapies, including inhibitors of JAK1 and JAK2. Ruxolitinib (previously known as INCB018424; Incyte Corporation, Wilmington, Delaware, USA) is a rationally designed potent oral JAK1 and JAK2 inhibitor that has undergone clinical trials in patients with PV, ET, and PMF. Ruxolitinib was approved on November 16, 2011 by the United States Food and Drug Administration for the treatment of intermediate or high-risk myelofibrosis (MF), including patients with PMF, post-PV MF, and post-ET MF. In randomized phase III studies, ruxolitinib treatment resulted in significant and durable reductions in splenomegaly and improvements in disease-related symptoms in patients with MF compared with placebo or best available therapy. The most common adverse events were anemia and thrombocytopenia, which were manageable and rarely led to discontinuation. This review addresses the cellular and molecular biology, and the clinical management of MPN.

This review focuses on topical issues in the biology and treatment of the myeloproliferative neoplasms (MPNs). Studies in transgenic mice suggest that BCR-ABL1 reduces the fraction of self-renewing 'leukemic' stem cells in the bone marrow but that some of these cells survive treatment with imatinib. This also seems to operate in humans. Data from models also strongly support the notion that JAK2(V617F) can initiate and sustain MPNs in mice; relevance to disease in humans is less clear. These data also support the hypothesis that level of JAK2(V617F) expression influences the MPN phenotype: higher levels favor erythrocytosis whereas lower levels favor thrombocytosis. Although TET2-mutations were thought to precede JAK2(V617F) in some persons with MPNs, it now appears that TET2 mutations may occur after JAK2(V617F). Further understanding of signal-transduction pathways activated in chronic myeloid leukemia suggests various possible targets for new therapies including the WNT/beta catenin, notch and hedgehog pathways. Finally, the clinical role of the new JAK2- and BCR-ABL1-inhibitors is considered. Much further progress is likely in several of these areas soon.

Ph-positive chronic myeloid leukemia (CML) and Ph-negative chronic myeloproliferative diseases (MPDs), characterized in many cases by the presence of the JAK2(V617F) mutation, have many features in common and yet also show fundamental differences. In this review, we pose five discrete and related questions relevant to both categories of hematological malignancy, namely: What are the mechanisms that underlie disease progression from a relatively benign or chronic phase? By what therapeutic methods might one target residual leukemia stem cells in CML? Is JAK2(V617F) the original molecular event in MPD? What epigenetic events must have a role in dictating disease phenotype in MPDs? And finally, Will the benefits conferred by current or future JAK2(V617F) inhibitors equal or even surpass the clinical success that has resulted from the use of tyrosine kinase inhibitors in CML? These and others questions must be addressed and in some cases should be answered in the foreseeable future.