B-lymphoblastic leukemia arising in a patient with chronic neutrophilic leukemia

Chronic Neutrophilic Leukemia: Advances in Diagnosis, Genetic Insights, and Management Strategies

CNL is a rare subtype of MPNs characterized by persistent neutrophilia, bone marrow hypercellularity, and specific genetic mutations, particularly in the CSF3R gene. Advances in molecular diagnostics have greatly enhanced our understanding of CNL, distinguishing it from other myeloproliferative disorders and refining diagnostic criteria. This review provides an updated overview of CNL, focusing on breakthroughs in genetic profiling, including novel mutations with potential prognostic value and implications for targeted therapy. We discuss current management strategies, emphasizing the role of JAK inhibitors, allogeneic stem cell transplantation, and evolving investigational treatments. Challenges in early diagnosis, therapeutic resistance, and future directions in research are also addressed, underscoring the need for a personalized medicine approach to improve outcomes for patients with CNL.

Rare case of simultaneous occurrence of chronic neutrophil leukemia and T lymphoblastic lymphoma: case report and literature review

Chronic neutrophil leukemia (CNL) is a rare and life-threatening disease. Cases of CNL combined with lymphoma are rare. Here, we report a case of CNL with T-acute lymphoblastic leukemia/lymphoma (T-ALL/LBL) in a 28-year-old male. After a regimen of ruxolitinib, VICLP (Vincristine, Idarubicin, Cyclophosphamide, Prednisone, Peg-asparaginase) regimen, high-dose cytarabine, and methotrexate regimens, the patient's bone marrow condition partially resolved. However, when the disease relapsed four months later, despite attempts with selinexor, venetoclax, and CAG(aclarubicin hydrochloride, Algocytidine, Granulocyte Stimulating Factor) chemotherapy, the leukocytes and peripheral blood primitive cells reduced, but the bone marrow did not achieve remission. This pathogenesis may be related to microenvironmental immune escape under prolonged inflammatory stimulation and gene disruption affecting protein function due to colony-stimulating factor 3 receptor gene (CSF3R) mutations. For this type of disease, early intervention may delay disease progression.

Research progress of additional pathogenic mutations in chronic neutrophilic leukemia

Chronic neutrophilic leukemia (CNL) is a rare type of myeloproliferative neoplasm (MPN). Due to its nonspecific clinical symptoms and lack of specific molecular markers, it was previously difficult to distinguish it from other diseases with increased neutrophils. However, the discovery of the CSF3R mutation in CNL 10 years ago and the update of the diagnostic criteria by the World Health Organization (WHO) in 2016 brought CNL into a new era of molecular diagnosis. Next-generation sequencing (NGS) technology has led to the identification of numerous mutant genes in CNL. While CSF3R is commonly recognized as the driver mutation of CNL, other mutations have also been detected in CNL using NGS, including mutations in other signaling pathway genes (CBL, JAK2, NARS, PTPN11) and chromatin modification genes (ASXL1, SETBP1, EZH2), DNA methylation genes (DNMT3A, TET2), myeloid-related transcription factor genes (RUNX1, GATA2), and splicing and RNA metabolism genes (SRSF2, U2AF1). The coexistence of these mutated genes and CSF3R mutations, as well as the different evolutionary sequences of clones, deepens the complexity of CNL molecular biology. The purpose of this review is to summarize the genetic research findings of CNL in the last decade, focusing on the common mutated genes in CNL and their clinical significance, as well as the clonal evolution pattern and sequence of mutation acquisition in CNL, to provide a basis for the appropriate management of CNL patients.

Chronic neutrophilic leukemia and atypical chronic myeloid leukemia: 2024 update on diagnosis, genetics, risk stratification, and management

Chronic neutrophilic leukemia (CNL) is a rare BCR::ABL1-negative myeloproliferative neoplasm (MPN) defined by persistent mature neutrophilic leukocytosis and bone marrow granulocyte hyperplasia. Atypical chronic myeloid leukemia (aCML) (myelodysplastic "[MDS]/MPN with neutrophilia" per World Health Organization [WHO]) is a MDS/MPN overlap disorder featuring dysplastic neutrophilia and circulating myeloid precursors. Both manifest with frequent hepatosplenomegaly and less commonly, bleeding, with high rates of leukemic transformation and death. The 2022 revised WHO classification conserved CNL diagnostic criteria of leukocytosis ≥25 × 109/L, neutrophils ≥80% with <10% circulating precursors, absence of dysplasia, and presence of an activating CSF3R mutation. ICC criteria are harmonized with those of other myeloid entities, with a key distinction being lower leukocytosis threshold (≥13 × 109/L) for cases CSF3R-mutated. Criteria for aCML include leukocytosis ≥13 × 109/L, dysgranulopoiesis, circulating myeloid precursors ≥10%, and at least one cytopenia for MDS-thresholds (ICC). In both classifications ASXL1 and SETBP1 (ICC), or SETBP1 ± ETNK1 (WHO) mutations can be used to support the diagnosis. Both diseases show hypercellular bone marrow due to a granulocytic proliferation, aCML distinguished by dysplasia in granulocytes ± other lineages. Absence of monocytosis, rare/no basophilia, or eosinophilia, <20% blasts, and exclusion of other MPN, MDS/MPN, and tyrosine kinase fusions, are mandated. Cytogenetic abnormalities are identified in ~1/3 of CNL and ~15-40% of aCML patients. The molecular signature of CNL is a driver mutation in colony-stimulating factor 3 receptor-classically T618I, documented in >80% of cases. Atypical CML harbors a complex genomic backdrop with high rates of recurrent somatic mutations in ASXL1, SETBP1, TET2, SRSF2, EZH2, and less frequently in ETNK1. Leukemic transformation rates are ~10-25% and 30-40% for CNL and aCML, respectively. Overall survival is poor: 15-31 months in CNL and 12-20 months in aCML. The Mayo Clinic CNL risk model for survival stratifies patients according to platelets <160 × 109/L (2 points), leukocytes >60 × 109/L (1 point), and ASXL1 mutation (1 point); distinguishing low- (0-1 points) versus high-risk (2-4 points) categories. The Mayo Clinic aCML risk model attributes 1 point each for: age >67 years, hemoglobin <10 g/dL, and TET2 mutation, delineating low- (0-1 risk factor) and high-risk (≥2 risk factors) subgroups. Management is risk-driven and symptom-directed, with no current standard of care. Most commonly used agents include hydroxyurea, interferon, Janus kinase inhibitors, and hypomethylating agents, though none are disease-modifying. Hematopoietic stem cell transplant is the only potentially curative modality and should be considered in eligible patients. Recent genetic profiling has disclosed CBL, CEBPA, EZH2, NRAS, TET2, and U2AF1 to represent high-risk mutations in both entities. Actionable mutations (NRAS/KRAS, ETNK1) have also been identified, supporting novel agents targeting involved pathways. Preclinical and clinical studies evaluating new drugs (e.g., fedratinib, phase 2) and combinations are detailed.

Chronic neutrophilic leukemia: 2022 update on diagnosis, genomic landscape, prognosis, and management

DISEASE OVERVIEW

Chronic neutrophilic leukemia (CNL) is a rare, often aggressive myeloproliferative neoplasm (MPN) defined by persistent mature neutrophilic leukocytosis, bone marrow granulocyte hyperplasia, and frequent hepatosplenomegaly. The 2013 seminal discovery of oncogenic driver mutations in colony-stimulating factor 3 receptor (CSF3R) in the majority of patients with CNL not only established its molecular pathogenesis but provided a diagnostic biomarker and rationale for pharmacological targeting.

DIAGNOSIS

In 2016, the World Health Organization (WHO) recognized activating CSF3R mutations as a central diagnostic feature of CNL. Other criteria include leukocytosis of ≥25 × 10⁹ /L comprising >80% neutrophils with <10% circulating precursors and rare blasts, and absence of dysplasia or monocytosis, while not fulfilling criteria for other MPN.

MANAGEMENT

There is currently no standard of care for management of CNL, due in large part to the rarity of disease and dearth of formal clinical trials. Most commonly used therapeutic agents include conventional oral chemotherapy (e.g., hydroxyurea), interferon, and Janus kinase (JAK) inhibitors, while hematopoietic stem cell transplant remains the only potentially curative modality.

DISEASE UPDATES

Increasingly comprehensive genetic profiling in CNL, including new data on clonal evolution, has disclosed a complex genomic landscape with additional mutations and combinations thereof driving disease progression and drug resistance. Although accurate prognostic stratification and therapeutic decision-making remain challenging in CNL, emerging data on molecular biomarkers and the addition of newer agents, such as JAK inhibitors, to the therapeutic arsenal, are paving the way toward greater standardization and improvement of patient care.

Co-Occurring CSF3R W791* Germline and Somatic T618I Driver Mutations Induce Early CNL and Clonal Progression to Mixed Phenotype Acute Leukemia

Chronic neutrophilic leukemia (CNL) relates to mutational CSF3R activation with membrane proximal CSF3R mutations such as T618I as driver mutations, but the significance of truncating mutations is not clarified. In CNL, concomitant mutations promote disease progression, but insight into longitudinal acquisition is incomplete. In this study, we investigated the role of co-occurring germline and somatic CSF3R mutations in CNL, and assessed the impact of clonal evolution on transformation to acute leukemia. We employed sequential next generation sequencing and SNP array karyotyping to assess clonal evolution in CNL of early manifestation age based on a 33-year-old patient. Germline vs. somatic mutations were differentiated using a sample from the hair follicle. To investigate a potential predisposition for CNL development and progression by germline CSF3R-W791*, allelic localizations were evaluated. We detected a somatic CSF3R-T618I mutation at 46% variant allele frequency (VAF) at the time of CNL diagnosis, which co-occurred with a CSF3R-W791* truncation at 50% VAF in the germline. Evaluation of allelic localization revealed CSF3R-T618I and W791* on the same allele. A concomitant ASXL1 mutation at 39% VAF increased to 48% VAF upon transformation to mixed phenotype acute leukemia (MPAL), which has both myeloid and lymphoid features. Clonal evolution further involved expansion of the CSF3R double-mutant clone to 90% VAF via copy neutral loss of heterozygosity on chromosome 1p and the emergence of a RUNX1 mutant subclone. Allogeneic transplantation induced complete remission. This study highlights that CNL not only transforms to AML but also to MPAL. The molecular evolution is especially interesting with a CSF3R-W791* mutation in the germline and acquisition of CSF3R-T618I on the same allele compatible with increased susceptibility for mutation acquisition facilitating RUNX1-related clonal transformation.

Chronic Neutrophilic Leukemia: A Literature Review of the Rare Myeloproliferative Pathology

Hematological malignancies often develop due to a vast spectrum of environmental and genetic etiologies. Chronic neutrophilic leukemia (CNL) can be described as a BCR-ABL1 (Philadelphia chromosome)-negative myeloproliferative neoplastic disease with various genetic mutations that may directly or indirectly play a role in its pathogenesis. A well-established mutation in CNL is the CSF3R (a cytokine receptor) which has been incorporated into the diagnostic criteria for the disease. However, evidence of other mutations such as SETBP1, ASXL1, and TET2 has also shed more light on the pathogenesis of this condition. Due to the unknown incidence and heterogeneous presentation of the disease, the diagnosis and management are often difficult and lack satisfactory data. The purpose of this review is to yield further insight into a disease that lacks awareness in the medical community. Using PubMed as a database, relevant studies and case reports were reviewed. The data compiled were used to acknowledge the disease in terms of etiology, clinical manifestation, molecular pathogenesis, and available treatment modalities. Though existing treatment modalities have been shown to induce clinical improvement, the outcomes are not reliable, and further research is required to reach a comprehensive "standard of care" for the disease.