Publisher9s Note: There is an Inside Blood Commentary on this article in this issue.

Mast cell disorders range from benign proliferations to systemic diseases that cause anaphylaxis and other diverse symptoms to mast cell neoplasms with varied clinical outcomes. Mastocytosis is the pathologic process of the accumulation of abnormal mast cells in different organs, mostly driven by KIT mutations, and can present as cutaneous mastocytosis, systemic mastocytosis (SM), and mast cell sarcoma. The WHO 5th edition classification divides systemic mastocytosis into bone marrow mastocytosis, indolent systemic mastocytosis, smoldering systemic mastocytosis, aggressive systemic mastocytosis, systemic mastocytosis with an associated hematologic neoplasm, and mast cell leukemia. The new ICC classifies SM slightly differently. The diagnosis of SM requires the integration of bone marrow morphologic, immunophenotypic, and molecular findings, as well as clinical signs and symptoms. Moreover, understanding the wide range of clinical presentations for patients with mast cell disorders is necessary for accurate and timely diagnosis. This review provides an updated overview of mast cell disorders, with a special emphasis on SM, including the latest approaches to diagnosis, prognostic stratification, and management of this rare disease.

Myeloproliferative neoplasms (MPNs) are a group of rare blood cancers characterized by the excessive production of blood cells in the bone marrow. These disorders arise from acquired genetic driver mutations, with or without underlying genetic predispositions, resulting in the uncontrolled production of red blood cells, white blood cells, or platelets. The excessive cell production and abnormal signaling from driver mutations cause chronic inflammation and a higher risk of blood clots and vascular complications. The primary goals of MPN treatment are to induce remission, improve quality of life and survival, as well as to reduce the risk of complications such as thrombosis, vascular events, and leukemic transformation. This review provides a comprehensive update on the diagnosis and therapeutic advancements in major MPN subtypes, including chronic myeloid leukemia, polycythemia vera, essential thrombocythemia, and primary myelofibrosis. It examines these complex diseases from a molecular and evolutionary perspective, highlighting key clinical trials’ long-term follow-up and therapies targeting driver mutations that have transformed treatment strategies. Additionally, several important advancements in addressing challenges such as anemia in myelofibrosis, along with promising emerging therapies, are also discussed.

Cancer stem cells (CSC) are hypothesized to promote tumor progression through innate chemoresistance and self-renewal. CSCs reside in the CD34+/CD38− immunophenotypic subpopulation of acute myeloid leukemia (AML). Isolation of CSCs from B-lymphoblastic leukemia (B-ALL) has proven difficult, and the cells of interest apparently are not isolated to the CD34+/CD38− compartment. This may be explained, in part, by temporal variations of CD34 and CD38 expression which result in stochastic cell state transitions (e.g., from CD34+/CD38+ to CD34+/CD38−). We present a mathematical model of these transitions and correlate salient findings with BCR::ABL1 status, minimal residual disease (MRD), and relapse in adult B-ALL. As the CSC hypothesis is well supported in AML, we focus on transitions to and from the hematopoietic stem cell compartment (CD34+/CD38−). Our analysis suggests the presence of dedifferentiating transitions to a CD34+/CD38− stem cell–like immunophenotype, especially in B-ALL with BCR::ABL1. In contrast, BCR::ABL1-negative patient samples have low CD34+/CD38− self-renewal rates and either high CD34+/CD38+ or CD34−/CD38+ incoming rates. High CD34+/CD38− self-renewal is also associated with positive MRD following induction chemotherapy. We find a lack of observable changes in cell state transitions between diagnosis and relapse specimens. Furthermore, simulated therapies targeting the stem cell–like compartment indicate that blocking transitions to the CD34+/CD38− state (i.e., blocking dedifferentiation) is more effective than promoting transitions from the CD34+/CD38− state toward other states (i.e., promoting differentiation) to reduce the proportion of CD34+/CD38− cells. The modeling framework used here is a novel, useful tool to infer prognosis and genotype from routine flow cytometry. Significance: Flow cytometry characterization of B-ALL samples (diagnosis, remission, and relapse) is used to parameterize a mathematical model of cell state transition rates and stratify patients for post-induction chemotherapy MRD.

Primary myelofibrosis (PMF) is a Philadelphia chromosome (Ph)-negative myeloproliferative neoplasm (MPN) that features clonal proliferation of atypical megakaryocytes and myeloid cells, fibrosis of the bone marrow, extramedullary hematopoiesis, and increased risk of leukemic transformation to acute myeloid leukemia (AML). With the widespread application of molecular studies, especially next generation sequencing (NGS), significant advances have reshaped our understanding of the molecular pathogenesis of PMF and the prognostic relevance of specific gene mutations. In this review, we summarize its clinicopathologic features, genetic and molecular findings, updated diagnostic criteria, and differential diagnosis. These updates have been incorporated into the 5th edition of the World Health Organization classification of Hematolymphoid Tumors (WHO-5th) and the 2022 International Consensus Classification (ICC), thereby improving diagnostic accuracy and risk stratification, both of which are essential for tailoring treatment strategies and enhancing patient outcomes.