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.

Venetoclax in combination with hypomethylating agent for the treatment of advanced myeloproliferative neoplasms and acute myeloid leukemia with extramedullary disease

The combination of venetoclax and hypomethylating agent (HMA/venetoclax) has emerged as a treatment option for patients with de novo acute myeloid leukemia (AML) who are unfit to receive intensive chemotherapy. In this single-center retrospective study, we evaluated clinical outcomes following treatment with HMA/venetoclax in 35 patients with advanced myeloproliferative neoplasms, myelodysplastic syndrome/myeloproliferative neoplasm overlap syndromes or AML with extramedullary disease. The composite complete remission (CR) rate (including confirmed/presumed complete cytogenetic response, acute leukemia response-complete, CR and CR with incomplete hematologic recovery) was 42.9% with median overall survival (OS) of 9.7 months. Complex karyotype was associated with inferior median OS (3.7 versus 12.2 months; p = 0.0002) and composite CR rate (22% versus 50.0%; p = 0.2444). Although SRSF2 mutations were associated with higher composite CR rate (80.0% versus 28.0%; p = 0.0082), this was not associated with longer median OS (10.9 versus 8.0 months; p = 0.2269). Future studies should include these patient subgroups.

Molecular Progression of Myeloproliferative and Myelodysplastic/Myeloproliferative Neoplasms: A Study on Sequential Bone Marrow Biopsies

Myeloproliferative neoplasms (MPN) and myelodysplastic/myeloproliferative neoplasms (MDS/MPN) both harbor the potential to undergo myelodysplastic progression or acceleration and can transform into blast-phase MPN or MDS/MPN, a form of secondary acute myeloid leukemia (AML). Although the initiating transforming events are yet to be determined, current concepts suggest a stepwise acquisition of (additional) somatic mutations-apart from the initial driver mutations-that trigger disease evolution. In this study we molecularly analyzed paired bone marrow samples of MPN and MDS/MPN patients with known progression and compared them to a control cohort of patients with stable disease course. Cases with progression displayed from the very beginning a higher number of mutations compared to stable ones, of which mutations in five (ASXL1, DNMT3A, NRAS, SRSF2 and TP53) strongly correlated with progression and/or transformation, even if only one of these genes was mutated, and this particularly applied to MPN. TET2 mutations were found to have a higher allelic frequency than the putative driver mutation in three progressing cases ("TET2-first"), whereas two stable cases displayed a TET2-positive subclone ("TET2-second"), supporting the hypothesis that not only the sum of mutations but also their order of appearance matters in the course of disease. Our data emphasize the importance of genetic testing in MPN and MDS/MPN patients in terms of risk stratification and identification of imminent disease progression.

The utility of a myeloid mutation panel for the diagnosis of myelodysplastic syndrome and myelodysplastic/myeloproliferative neoplasm

INTRODUCTION

The diagnosis of myelodysplastic syndromes (MDS) and myelodysplastic/myeloproliferative neoplasms (MDS/MPN) is based on morphology and cytogenetics/FISH findings per 2017 WHO classification. With rare exceptions, somatic mutations have not been incorporated as the diagnostic criteria.

METHODS

We analyzed the utility of mutational analysis with a targeted 54-gene or 40-gene next-generation sequencing (NGS) panel in the diagnosis of MDS and MDS/MPN.

RESULTS

We retrospectively collected 92 patients who presented with unexplained cytopenia with or without cytosis, including 32 low-grade MDS (MDS-L), 18 high-grade MDS (MDS-H), 5 therapy-related MDS (MDS-TR), 19 MDS/MPN, and 18 negative cases. Of 92 patients, 197 somatic mutations involving 38 genes were detected and had variant allele frequency (VAF) ranging from 3% to 99%. The most common mutated genes were TET2, ASXL1, RUNX1, TP53, SRSF2, and SF3B1. MDS-L, MDS-H, MDS-TR, and MDS/MPN showed an average number of somatic mutations with a mean VAF of 1.9/33%, 2.6/30%, 2/36%, and 4/41%, respectively. SF3B1 mutations were exclusively observed in MDS-L and MDS/MPN. TP53 gene mutations were more frequently seen in MDS-H and MDS-TR. Among 34 patients with a diagnosis of MDS or MDS/MPN with normal cytogenetics, 31 patients (91%) had at least 1 mutation and 24 patients (71%) had ≥2 mutations with ≥10% VAF.

CONCLUSION

A myeloid mutational panel provides additional evidence of clonality besides cytogenetics/FISH studies in the diagnosis of cytopenia with or without cytosis. Two or more mutations with ≥10% VAF highly predicts MDS and MDS/MPN with a positive predictive value of 100%.

A focused review of hematopoietic neoplasms occurring in the therapy-related setting

Hematological neoplasms developed in patients with a history of cytotoxic therapies comprise a group of diseases with a poor clinical outcome, and collectively categorized as "therapy-related myeloid neoplasms" (t-MN) in the 2008 World Health Organization (WHO) Classification. In recent years, numerous publications have emerged, and these studies have greatly expanded the scope of our understanding in this field. We here focused our review on several selected areas including secondary malignancies occurring in patients with autoimmune diseases; radiation therapy alone as a causative agent; the similarity and differences between therapy-related myelodysplastic syndromes (t-MDS) and acute myeloid leukemia (t-AML); clinical behavior and treatment outcome of t-AML patients with favorable cytogenetics; the incidence and clinical features of myelodysplastic/myeloproliferative neoplasms, as well as acute lymphoblastic leukemia and myeloproliferative neoplasms in patients with prior cytotoxic exposure. These recent studies have shown that therapy-related hematopoietic neoplasms are heterogeneous, and may manifest in various forms, more complex than we have recognized previously. Cytogenetic abnormalities and underlying mutations are likely to be the major factors dictating prognosis.

Refractory anemia with ring sideroblasts

Refractory anemia with ring sideroblasts (RARS) is a subtype of myelodysplastic syndrome (MDS) characterized by 15% or more ring sideroblasts in the bone marrow according to the WHO classification. After Perls staining, ring sideroblasts are defined as erythroblasts in which there are 5 or more siderotic granules covering at least a third of the nuclear circumference. The iron deposited in perinuclear mitochondria of ring sideroblasts is present in the form of mitochondrial ferritin. The molecular basis of MDS with ring sideroblasts has remained unknown until recently. In 2011, whole exome sequencing studies revealed somatic mutations of SF3B1, a gene encoding a core component of RNA splicing machinery, in myelodysplasia with ring sideroblasts. The close relationship between SF3B1 mutation and ring sideroblasts is consistent with a causal relationship, and makes SF3B1 the first gene to be associated with a specific morphological feature in MDS. RARS is mainly characterized by isolated anemia due to ineffective erythropoiesis, and its clinical course is generally benign, although there is a tendency to worsening of anemia in most patients over time. By contrast, refractory cytopenia with multilineage dysplasia and ring sideroblasts (RCMD-RS) is characterized by pancytopenia and dysplasia in two or more myeloid cell lineages. More importantly, patients with RCMD-RS have a higher risk of developing bone marrow failure or progressing to acute myeloid leukemia (AML). Refractory anemia with ring sideroblasts (RARS-T) associated with marked thrombocytosis is a myelodysplastic/myeloproliferative neoplasm associated with both SF3B1 and JAK2 or MPL mutations. RARS-T may develop from an SF3B1 mutated RARS through the acquisition of a JAK2 or MPL mutations in a subclone of hematopoietic cells.

Molecular basis of myelodysplastic syndromes

Myelodysplastic syndromes (MDS) are myeloid neoplasms characterized by dysplasia in one or more cell lines, ineffective hematopoiesis and variable risk of progression to acute myeloid leukemia. In the past few years, important steps have been taken in characterizing the molecular basis of MDS. More recently, somatic mutations in genes encoding core components of the RNA splicing machinery have been detected in high proportions of MDS patients, and are shown to be founding mutations in many instances. These mutations have different clinical significance, and their incorporation into current stratification systems might improve risk assessment in MDS.