Atypical chronic myeloid leukemia: a rare entity with management challenges

Differential diagnoses and the mutational landscape of myelodysplastic/myeloproliferative neoplasm with neutrophilia: A case report

Myelodysplastic/myeloproliferative neoplasm with neutrophilia (MDS/MPN-N; previously referred to as atypical chronic myeloid leukemia) is a type of myelodysplastic syndrome/myeloproliferative neoplasm. A molecular genetic precondition for diagnosis is BCR::ABL negativity; further diagnostic criteria include clinicopathological assessments, such as peripheral blood leukocyte counts, the number of neutrophils and their precursors, and the presence of dysgranulopoiesis. The present case report highlights the importance of differential diagnoses with a stringent diagnostic workup according to the 5th Edition of the World Health Organization Classification of Hematolymphoid Tumors. A systematic review of the literature from 2013 to 2022 covering the mutational landscape of MDS/MPN-N was also performed to highlight recent improvements in the molecular genetic diagnostics of this disease.

Myelodysplastic Syndromes/Myeloproliferative Overlap Neoplasms and Differential Diagnosis in the WHO and ICC 2022 Era: A Focused Review

The myelodysplastic syndromes/myeloproliferative neoplasms (MDS/MPN) category comprises a varied group of myeloid neoplastic diseases characterized by clinical and pathologic overlapping features of both myelodysplastic and myeloproliferative neoplasms. For these reasons, these tumors are challenging in terms of diagnosis. The recent World Health Organization (WHO) 2022 classification and the International Consensus Classification (ICC) made changes in the classification of MDS/MPN compared to the previous 2016 WHO classification and improved the diagnostic criteria of these entities. The aim of this review is to describe the main entities reported in the more recent classifications, focusing on chronic myelomonocytic leukemia (CMML), MDS/MPN with neutrophilia (or atypical CML [aCML]), and MDS/MPN with SF3B1 mutation and thrombocytosis/MDS/MPN with ring sideroblasts and thrombocytosis. A particular emphasis is given to the differential diagnosis and analysis of subtle divergences and semantic differences between the WHO classification and the ICC for these entities.

Advances in myelodysplastic/myeloproliferative neoplasms

The myelodysplastic syndrome/myeloproliferative neoplasms (MDS/MPN) category includes a heterogeneous group of diseases characterized by the co-occurrence of clinical and pathologic features of both myelodysplastic and myeloproliferative neoplasms. The recently published International Consensus Classification of myeloid neoplasms revised the entities included in the MDS/MPN category as well as criteria for their diagnosis. In addition to the presence of one or more increased peripheral blood cell counts as evidence of myeloproliferative features, concomitant cytopenia as evidence of ineffective hematopoiesis is now an explicit requirement to diagnose the diseases included in this category. The increasing availability of modern gene sequencing has allowed better understanding of the biologic characteristics of these myeloid neoplasms. The presence of specific mutations in the appropriate clinicopathologic context is now included in the diagnostic criteria for some of MDS/MPN entities. In this review, we highlight what has changed in the diagnostic criteria of MDS/MPN from the WHO 2016 classification while providing practical guidance in diagnosing these diseases.

Trametinib: Could It Be a Promising Drug to Treat Atypical Chronic Myeloid Leukemia?

Atypical chronic myeloid leukemia (aCML) is a rare disease that is currently classified under the myelodysplastic (MDS)/myeloproliferative neoplasm (MPN) disease spectrum. MDS/MPN diseases are characterized by the absence of the Philadelphia (Ph) chromosome and the overlap between bone marrow fibrosis and dysplastic features. The Ph chromosome, resulting from BCR-ABL1 translocation, helps to distinguish aCML from chronic myeloid leukemia (CML). The currently reported incidence of aCML is imprecise because aCML is diagnosed primarily based on morphological features and other unspecified laboratory findings, and there is an especially high chance of under-diagnosis of aCML and other MDS/MPN diseases. Recent advances in next-generation sequencing (NGS) have allowed a greater understanding of the nature of aCML, providing better opportunities to achieve higher diagnostic accuracy and for the use of more targeted treatment to achieve better outcomes. Herein, we present a case of a 68-year-old woman who came to our hospital complaining of shortness of breath, fatigue, and weakness, who was found to have significantly increased leukocytosis, hepatosplenomegaly, and was negative for the Ph chromosome. Further investigations with NGS revealed mutations in ASXL1, GATA2, NRAS, and SRSF2 but not CSF3R. In addition to this, peripheral smear and bone marrow aspiration findings were suggestive of aCML based on specific morphological findings. Since the patient was ineligible for a stem cell transplant (SCT), symptomatic treatment was started with cell transfusion; however, the patient continued to have symptomatic anemia that required multiple transfusions. A trial with trametinib, a mitogen-activated protein kinase kinase (MEK) inhibitor, was later started as a targeted therapy based on one of her genetic mutations. Interestingly, the patient’s blood counts stabilized, she reported feeling better, and she did not need any blood transfusions for four consecutive months during treatment with trametinib. Unfortunately, our patient later died from sepsis resulting from secondary infections. In light of the significant advancements in NGS, clinicians should always consider utilizing it as a helpful tool to not only establish a rare diagnosis of aCML but also to offer the best available targeted therapy when applicable. This might alleviate the burden associated with the poor prognosis of aCML.

Molecular Pathogenesis of BCR-ABL-Negative Atypical Chronic Myeloid Leukemia

Atypical chronic myeloid leukemia is a rare disease whose pathogenesis has long been debated. It currently belongs to the group of myelodysplastic/myeloproliferative disorders. In this review, an overview on the current knowledge about diagnosis, prognosis, and genetics is presented, with a major focus on the recent molecular findings. We describe here the molecular pathogenesis of the disease, focusing on the mechanisms of action of the main mutations as well as on gene expression profiling. We also present the treatment options focusing on emerging targeted therapies.

Atypical Chronic Myeloid Leukemia: New Developments from Molecular Diagnosis to Treatment

Atypical Chronic Myeloid Leukemia, BCR-ABL1 negative (aCML) is a rare hematological entity, included in the group of myelodysplastic (MDS)/myeloproliferative (MPN) overlap syndromes. It is characterized by an aggressive course, a high rate of acute myeloid leukemia (AML) transformation, and a dismal outcome. The clinical presentation includes splenomegaly and leukocytosis with neutrophilia and left-shifted granulocytosis accompanied by granulocytic dysplasia and sometimes multilineage dysplasia. In past years, the disease incidence was likely underestimated, as diagnosis was only based on morphological features. Recently, the improving knowledge in the molecular biology of MDS/MPN neoplasms has made it possible to distinguish aCML from other overlapping syndromes, basing on next generation sequencing. Among the most commonly mutated genes, several involve the Jak-STAT, MAPK, and ROCK signaling pathways, which could be actionable with targeted therapies that are already used in clinical practice, opening the way to tailored treatment in aCML. However, currently, there are few data available for small samples, and allogeneic transplant remains the only curative option for eligible patients.

Voriconazole as a secondary prophylaxis for cryptococcal meningitis during hematopoietic stem cell transplantation

Antifungal prophylaxis is crucial for successful hematopoietic stem cell transplantation (HSCT). Maintenance therapy with fluconazole (FLCZ) is generally prescribed as secondary prophylaxis in patients with human immunodeficiency virus infection and non-immunocompromised hosts. However, previous reports have revealed that FLCZ is insufficient as a secondary prophylaxis for cryptococcal infection in HSCT cases. There is no well-established evidence of effective secondary prophylaxis against cryptococcal infection in conditions of severe immunosuppression, such as in HSCT. Herein, we report a case of atypical chronic myeloid leukemia (aCML) presenting with cryptococcal meningitis. A 58-year-old man with progressive leukocytosis and headache was referred to our hospital. Bone marrow biopsy revealed aCML. Because the estimated overall survival was limited, HSCT was indicated. Furthermore, enhanced magnetic resonance imaging and lumbar puncture aided in diagnosing cryptococcal meningitis, which was treated with a combination therapy comprising liposomal amphotericin B and 5-fluorocystine for 28 days. Given the high recurrence rate of cryptococcal meningitis, voriconazole (VRCZ) dose was calculated using the trough concentration of VRCZ in the cerebrospinal fluid. Eventually, HSCT was successfully performed at an appropriate therapeutic range of VRCZ. To the best of our knowledge, there is no case report on HSCT with secondary prophylaxis against cryptococcal meningitis. Our report thus emphasizes the efficacy of VRCZ maintenance therapy as secondary prophylaxis for cryptococcal infection.

Atypical Chronic Myeloid Leukemia: Where Are We Now?

Atypical chronic myeloid leukemia, BCR-ABL1 negative (aCML) is a rare myelodysplastic syndrome (MDS)/myeloproliferative neoplasm (MPN) with a high rate of transformation to acute myeloid leukemia, and poor survival. Until now, the diagnosis has been based on morphological grounds only, possibly making the real frequency of the disease underestimated. Only recently, new insights in the molecular biology of MDS/MPN syndromes have deepened our knowledge of aCML, enabling us to have a better molecular profile of the disease. The knowledge gleaned from next generation sequencing has complemented morphologic and laboratory WHO criteria for myeloid neoplasms and can provide greater specificity in distinguishing aCML from alternative MDS/MPN or MPNs. The most commonly mutated genes (>20%) in aCML are SETBP1, ASXL1, N/K-RAS, SRSF2, and TET2, and less frequently (< 10%) CBL, CSFR3, JAK2, EZH2, and ETNK1. Several of these mutations affect the JAK-STAT, MAPK, and ROCK signaling pathways, which are targetable by inhibitors that are already in clinical use and may lead to a personalized treatment of aCML patients unfit for allogeneic transplant, which is currently the only curative option for fit patients. In this review, we present two emblematic clinical cases and address the new molecular findings in aCML and the available treatment options.

Circ_0009910 promotes imatinib resistance through ULK1-induced autophagy by sponging miR-34a-5p in chronic myeloid leukemia

BACKGROUND

The occurrence in drug resistance of chronic myeloid leukemia (CML) was accompanied by autophagy activation. Abnormal circular RNAs (circRNAs) participated in this progression. This study attempted to investigate the potential role of circ_0009910 in imatinib resistance of CML cells.

METHODS

The expression of circ_0009910 and miR-34a-5p was measured by quantitative real-time polymerase chain reaction (qRT-PCR). The characterization of circ_0009910 was investigated using oligo (dT)18 primers, Actinomycin D and RNase R. Cell viability (IC₅₀ value) and apoptosis were assessed by Cell Counting Kit-8 (CCK8) assay and flow cytometry assay, respectively. The relative protein expression was quantified by western blot. The relationship among miR-34a-5p, circ_0009910 and ULK1 was predicted by online bioinformatics tool, and verified by dual-luciferase reporter assay and RNA immunoprecipitation (RIP).

RESULTS

The expression of circ_0009910 was up-regulated in the serum of imatinib-resistance CML patients and K562/R cells, and associated with unfavorable clinicopathologic features. Circ_0009910 in K562 and K562/R cells was mainly localized in the cytoplasm. Circ_0009910 knockdown inhibited cell proliferation and autophagy, but induced apoptosis in K562/R cells. Circ_0009910 targeted miR-34a-5p to regulate ULK1. MiR-34a-5p depression rescued the effects of circ_0009910 knockdown on apoptosis and autophagy in K562/R cells.

CONCLUSION

Circ_0009910 accelerated imatinib-resistance in CML cells by modulating ULK1-induced autophagy via targeting miR-34a-5p, providing a potential target in imatinib resistance of CML.

Atypical CML- the role of morphology and precision genomics

Atypical chronic myeloid leukemia is an esoteric myeloid malignancy with features of both myeloproliferative and myelodysplastic syndromes. This disease is characterized primarily by morphologic-based criteria, and has clinical and molecular features overlapping with other myeloid malignancies. No one molecular abnormality is specific, and multiple mutations are often present in various combinations, due to the malignant multi-step clonal evolution of myeloid malignancies. In this review, we will address what we know about atypical chronic myeloid leukemia; evaluate how the molecular landscape in myeloid malignancies overlaps, and discuss what we can learn by incorporating individualized precision genomic strategies.

Next-generation sequencing reveals unique combination of mutations in cis of CSF3R in atypical chronic myeloid leukemia

Background

Atypical chronic myeloid leukemia (aCML) is a hematologic disorder characterized by leukocytosis with increased dysplastic neutrophils and their precursors. In CSF3R gene, the activation mutation including T618I is frequently reported in aCML but is rarely accompanied by truncation mutations. Herein, we report a unique aCML patient with two CSF3R mutations (T618I and Y779*) in the same DNA strand.

Methods

High‐coverage next‐generation sequencing for 40 genes related with myeloid leukemia was performed. Sanger sequencing was performed to confirm CSF3R mutations. To confirm whether two CSF3R mutations are in cis or not, TA cloning was used. Clinical information and bone marrow pathology were reviewed by two hematopathologists.

Results

In the patient diagnosed with aCML in bone marrow study, two CSF3R mutations, (T618I and Y779*) a SETBP1 mutation (G870S) and an U2AF1 mutation (Q157P), were identified by high‐coverage next‐generation sequencing. The two CSF3R mutations were confirmed to be located in the same DNA strand by TA cloning, indicating that the two mutations are harbored in one malignant clone. The SETBP1 mutation is known to be related with poor prognosis in aCML. Likewise, the patient was refractory to hydroxyurea and showed disease progression. Additionally, we discussed the potential therapeutic targets by reviewing the molecular profile of the patient.

Conclusion

We believe that the accurate diagnosis and maximum therapeutic chance could be achieved by profiling the mutations and their characteristics.