Chronic neutrophilic leukemia with JAK2 gene mutation

Chronic neutrophilic leukemia: new science and new diagnostic criteria

Chronic neutrophilic leukemia (CNL) is a distinct myeloproliferative neoplasm defined by persistent, predominantly mature neutrophil proliferation, marrow granulocyte hyperplasia, and frequent splenomegaly. The seminal discovery of oncogenic driver mutations in CSF3R in the majority of patients with CNL in 2013 generated a new scientific framework for this disease as it deepened our understanding of its molecular pathogenesis, provided a biomarker for diagnosis, and rationalized management using novel targeted therapies. Consequently, in 2016, the World Health Organization (WHO) revised the diagnostic criteria for CNL to reflect such changes in its genomic landscape, now including the presence of disease-defining activating CSF3R mutations as a key diagnostic component of CNL. In this communication, we provide a background on the history of CNL, its clinical and hemopathologic features, and its molecular anatomy, including relevant additional genetic lesions and their significance. We also outline the recently updated WHO diagnostic criteria for CNL. Further, the natural history of the disease is reviewed as well as potential prognostic variables. Finally, we summarize and discuss current treatment options as well as prospective novel therapeutic targets in hopes that they will yield meaningful improvements in patient management and outcomes.

Chronic neutrophilic leukaemia and plasma cell-related neutrophilic leukaemoid reactions

Many cases reported as 'chronic neutrophilic leukaemia' have had an associated plasma cell neoplasm. Recent evidence suggests that the great majority of such cases represent a neutrophilic leukaemoid reaction to the underlying multiple myeloma or monoclonal gammopathy of undetermined significance. We have analysed all accessible reported cases to clarify the likely diagnosis and to ascertain whether toxic granulation, Döhle bodies and an increased neutrophil alkaline phosphatase score were useful in making a distinction between chronic neutrophilic leukaemia and a neutrophilic leukaemoid reaction. We established that all these changes occur in both conditions. Toxic granulation and Döhle bodies are more consistently present in leukaemoid reactions but also occur quite frequently in chronic neutrophilic leukaemia. The neutrophil alkaline phosphatase score is increased in both conditions and is of no value in making a distinction.

Diagnosis, complications and management of chronic neutrophilic leukaemia: A case report

Chronic neutrophilic leukemia (CNL) is a rare myeloproliferative neoplasm characterized by sustained neutrophilia and the absence of the Philadelphia chromosome or the BCR-ABL1 fusion gene. The present study reports the case of a 59-year-old Caucasian female that was referred to The Francisco Gentil Portuguese Institute of Oncology (Porto, Portugal) with constitutional symptoms (mainly asthenia), marked leukocytosis (51.33×10⁹/l with 90% neutrophils), macrocytic anemia and splenomegaly. Bone marrow aspiration and biopsy revealed hypercellular marrow with clear predominance of segmented neutrophils. The karyotype was normal and the BCR-ABL1 fusion gene was not detected. After excluding a leukemoid reaction, a diagnosis of CNL was established. The clinical follow-up was complicated by hemorrhagic brain lesions and relapsing episodes of erythematous, well-demarcated and painful subcutaneous nodular lesions, consistent with Sweet's syndrome (SS). Multiple treatment strategies were administered, including use of hydroxyurea, imatinib and intensive chemotherapy. Nevertheless, progression was documented and the patient succumbed at 28 months post-diagnosis. The clinical course of CNL varies, and can be complicated by cerebral hemorrhage, blastic transformation or infection. Dermatological manifestations such as SS have seldom been reported in association. No evidence-based treatment currently exists and the majority of our knowledge is based on results from case reports and small series.

Molecular genetics of chronic neutrophilic leukemia, chronic myelomonocytic leukemia and atypical chronic myeloid leukemia

According to the 2008 World Health Organization classification, chronic neutrophilic leukemia, chronic myelomonocytic leukemia and atypical chronic myeloid leukemia are rare diseases. The remarkable progress in our understanding of the molecular genetics of myeloproliferative neoplasms and myelodysplastic/myeloproliferative neoplasms has made it clear that there are some specific genetic abnormalities in these 3 rare diseases. At the same time, there is considerable overlap among these disorders at the molecular level. The various combinations of genetic abnormalities indicate a multi-step pathogenesis, which likely contributes to the marked clinical heterogeneity of these disorders. This review focuses on the current knowledge and challenges related to the molecular pathogenesis of chronic neutrophilic leukemia, chronic myelomonocytic leukemia and atypical chronic myeloid leukemia and relationships between molecular findings, clinical features and prognosis.

The molecular genetics of chronic neutrophilic leukaemia: defining a new era in diagnosis and therapy

PURPOSE OF REVIEW

In the current WHO classification of myeloid disorders, chronic neutrophilic leukaemia (CNL) is recognized as a myeloproliferative neoplasm characterized by sustained neutrophilic leukocytosis, hepatosplenomegaly and bone marrow granulocytic hyperplasia without evidence of dysplasia, BCR-ABL1 or rearrangements of PDGFRA, PDGFRB or FGFR1. This diagnosis is contingent upon exclusion of underlying causes of reactive neutrophilia particularly if evidence of myeloid clonality is lacking. The lack of a specific molecular marker has left the diagnosis to be largely one of exclusion. Recently, the molecular landscape shifted with the discovery of specific oncogenic mutations in the colony-stimulating factor 3 receptor gene (CSF3R) in CNL patients. We review the implications for diagnosis, pathogenesis and potential for new therapeutic options.

RECENT FINDINGS

In 2013, oncogenic mutations in CSF3R were identified in a majority of patients with CNL and demonstrated that their downstream signalling was sensitive to known kinase inhibitors. This discovery was then validated with the demonstration of 100% CSF3R mutational frequency (predominately CSF3RT618I) in strictly WHO-defined CNL. Simultaneously, novel somatic mutations in SETBP1 were found to be enriched in CNL with possible prognostic significance.

SUMMARY

CNL appears to be driven by specific somatic activating CSF3R mutations. These bestow susceptibility to known kinase inhibitors, opening the door to novel specific therapeutic options for CNL. The diagnosis of CNL will no longer be one only of exclusion, and revision of the current WHO diagnostic criteria is expected to include the molecular criterion of CSF3R mutation positivity.

Chronic neutrophilic leukemia 2014: Update on diagnosis, molecular genetics, and management

DISEASE OVERVIEW

Chronic neutrophilic leukemia (CNL) is a myeloproliferative neoplasm characterized by sustained, mature neutrophilic leukocytosis, splenomegaly, and bone marrow granulocytic hyperplasia.

DIAGNOSIS

Key diagnostic criteria include leukocytosis of >25 × 10(9) /l (of which >80% are neutrophils) with <10% and <1% circulating immature granulocytes and myeloblasts, respectively. There should be no dysplasia, monocytosis, molecular evidence of BCR-ABL1, PDGFRA, PDGFRB, or FGRF1 rearrangements and no identifiable cause for physiologic neutrophilia or, if present, demonstration of myeloid clonality. DEVELOPMENTS IN MOLECULAR GENETICS: Recently, CNL has been shown to be specifically driven by somatic activating mutations of CSF3R, most commonly CSF3R T618I. As such, the diagnosis of CNL will no longer be one of exclusion only, and revision of the current WHO classification is anticipated to include the molecular criterion of mutated CSF3R.