Acute Myeloid Leukemia and Other Types of Disease Progression in Myeloproliferative Neoplasms

Progression in Myeloid Neoplasms: Beyond the Myeloblast

Disease progression in myelodysplastic syndromes (MDS), myelodysplastic-myeloproliferative neoplasms (MDS/MPN), and myeloproliferative neoplasms (MPN), altogether referred to as myeloid neoplasms (MN), is a major source of mortality. Apart from transformation to acute myeloid leukemia, the clinical progression of MN is mostly due to the overgrowth of pre-existing hematopoiesis by the MN without an additional transforming event. Still, MN may evolve along other recurrent yet less well-known scenarios: (1) acquisition of MPN features in MDS or (2) MDS features in MPN, (3) progressive myelofibrosis (MF), (4) acquisition of chronic myelomonocytic leukemia (CMML)-like characteristics in MPN or MDS, (5) development of myeloid sarcoma (MS), (6) lymphoblastic (LB) transformation, (7) histiocytic/dendritic outgrowths. These MN-transformation types exhibit a propensity for extramedullary sites (e.g., skin, lymph nodes, liver), highlighting the importance of lesional biopsies in diagnosis. Gain of distinct mutations/mutational patterns seems to be causative or at least accompanying several of the above-mentioned scenarios. MDS developing MPN features often acquire MPN driver mutations (usually JAK2), and MF. Conversely, MPN gaining MDS features develop, e.g., ASXL1, IDH1/2, SF3B1, and/or SRSF2 mutations. Mutations of RAS-genes are often detected in CMML-like MPN progression. MS ex MN is characterized by complex karyotypes, FLT3 and/or NPM1 mutations, and often monoblastic phenotype. MN with LB transformation is associated with secondary genetic events linked to lineage reprogramming leading to the deregulation of ETV6, IKZF1, PAX5, PU.1, and RUNX1. Finally, the acquisition of MAPK-pathway gene mutations may shape MN toward histiocytic differentiation. Awareness of all these less well-known MN-progression types is important to guide optimal individual patient management.

Abnormal B-lymphoblasts in myelodysplastic syndromes and myeloproliferative neoplasms other than chronic myeloid leukemia

BACKGROUND

Lineage infidelity is characteristic of mixed phenotype acute leukemia and is also seen in blast phase of chronic myeloid leukemia (CML), myeloid/lymphoid neoplasia with eosinophilia and gene rearrangements, and subtypes of acute myeloid leukemia. Driver genetic events often occur in multipotent progenitor cells in myeloid neoplasms, suggesting that multilineage output may be more common than appreciated. This phenomenon is not well studied in myelodysplastic syndrome (MDS) and non-CML myeloproliferative neoplasms (MPN).

METHODS

We systematically evaluated phenotypic lineage infidelity by reviewing bone marrow pathology and flow cytometry (FC) studies of 1262 consecutive patients with a diagnosis of MDS and/or non-CML MPN. We assessed B- and T-cells in these patients by FC. When abnormal B-lymphoblast (ABLB) populations were detected, we additionally evaluated immature B-cells using a high sensitivity FC assay for B-lymphoblastic leukemia/lymphoma (B-ALL).

RESULTS

We identified 9 patients (7 MDS, 7/713, 1%; 2 non-CML MPN, 2/312, 0.6%; 0 in MDS/MPN) with low-level ABLB populations (0.012%-3.6% of WBCs in marrow) with abnormal immunophenotypes. Genetic studies on flow sorted cell populations confirmed that some ABLB populations were clonally related to myeloid blasts (4/6, 67%). On follow-up, ABLB populations in 8/9 patients remained stable or disappeared. Only 1 case progressed to B-ALL.

CONCLUSIONS

These findings demonstrate that phenotypically detectable abnormal immature B lineage output occurs in MDS and non-CML MPN, albeit rarely. While presence of ABLB does not necessarily reflect blast crisis, the underlying disease biology of our findings may ultimately be relevant to patient management and warrants further investigation.

Progression in Ph-Chromosome-Negative Myeloproliferative Neoplasms: An Overview on Pathologic Issues and Molecular Determinants

Progression in Ph-chromosome-negative myeloproliferative neoplasms (MPN) develops with variable incidence and time sequence in essential thrombocythemia, polycythemia vera, and primary myelofibrosis. These diseases show different clinic-pathologic features and outcomes despite sharing deregulated JAK/STAT signaling due to mutations in either the Janus kinase 2 or myeloproliferative leukemia or CALReticulin genes, which are the primary drivers of the diseases, as well as defined diagnostic criteria and biomarkers in most cases. Progression is defined by the development or worsening of marrow fibrosis or the progressive increase in the marrow blast percentage. Progression is often related to additional genetic aberrations, although some can already be detected during the chronic phase. Detailed scoring systems for clinical usage that are mostly applied in patients with primary myelofibrosis have been defined, and the most recent ones include cytogenetic and molecular parameters with prognostic significance. Additional different clinic-pathologic changes have been reported that may occur during the course of the disease and that are, at present, classified as WHO-defined types of progression, although they likely represent such an event. The present review is meant to provide an updated overview on progression in Ph-chromosome-negative MPN, with a major focus on the pathologic side.

Progression in Ph-Chromosome-Negative Myeloproliferative Neoplasms: An Overview on Pathologic Issues and Molecular Determinants

Progression in Ph-chromosome-negative myeloproliferative neoplasms (MPN) develops with variable incidence and time sequence in essential thrombocythemia, polycythemia vera, and primary myelofibrosis. These diseases show different clinic-pathologic features and outcomes despite sharing deregulated JAK/STAT signaling due to mutations in either the Janus kinase 2 or myeloproliferative leukemia or CALReticulin genes, which are the primary drivers of the diseases, as well as defined diagnostic criteria and biomarkers in most cases. Progression is defined by the development or worsening of marrow fibrosis or the progressive increase in the marrow blast percentage. Progression is often related to additional genetic aberrations, although some can already be detected during the chronic phase. Detailed scoring systems for clinical usage that are mostly applied in patients with primary myelofibrosis have been defined, and the most recent ones include cytogenetic and molecular parameters with prognostic significance. Additional different clinic-pathologic changes have been reported that may occur during the course of the disease and that are, at present, classified as WHO-defined types of progression, although they likely represent such an event. The present review is meant to provide an updated overview on progression in Ph-chromosome-negative MPN, with a major focus on the pathologic side.

Combination of myeloproliferative neoplasm driver gene activation with mutations of splice factor or epigenetic modifier genes increases risk of rapid blastic progression

OBJECTIVES

Myeloproliferative neoplasms (MPN) comprising polycythemia vera (PV), essential thrombocythemia (ET) and primary myelofibrosis (PMF) follow a bi-phasic course of disease with fibrotic and/or blastic progression. At presentation in the chronic phase, currently there are only insufficient tools to predict the risk of progression in individual cases.

METHODS

In this study, chronic phase MPN (16 PMF, 11 PV, and 11 MPN unclassified) with blastic transformation during course of disease (n = 38, median follow-up 5.3 years) were analyzed by high-throughput sequencing. MPN cases with a comparable follow-up period and without evidence of blast increase served as control (n = 63, median follow-up 5.8 years).

RESULTS

Frequent ARCH/CHIP-associated mutations (TET2, ASXL1, DNMT3A) found at presentation were not significantly associated with blastic transformation. By contrast, mutations of SRSF2, U2AF1, and IDH1/2 at first presentation were frequently observed in the progression cohort (13/38, 34.2%) and were completely missing in the control group without blast transformation during follow-up (P = .0007 for SRSF2; P = .0063 for U2AF1 and IDH1/2).

CONCLUSION

Unlike frequent ARCH/CHIP alterations (TET2, ASXL1, DNMT3A), mutations in SRSF2, IDH1/2, and U2AF1 when manifest already at first presentation provide an independent risk factor for rapid blast transformation of MPN.

Progression, transformation, and unusual manifestations of myelodysplastic syndromes and myelodysplastic-myeloproliferative neoplasms: lessons learned from the XIV European Bone Marrow Working Group Course 2019

Disease progression in myelodysplastic syndromes (MDS) and myelodysplastic-myeloproliferative neoplasms (MDS/MPN) is a major source of mortality. The European Bone Marrow Working Group organized a dedicated workshop to address MDS and MDS/MPN progression, and myeloid neoplasms with histiocytic and lymphoblastic outgrowths in 2019 in Frankfurt, Germany. In this report, we summarize clinical, histopathological, and molecular features of 28 cases. Most cases illustrate that prognostic mutational profiles change during follow-up due to accumulation of high-risk mutations in the trunk clone, and that results from repeated molecular testing can often explain the clinical progression, suggesting that regular genetic testing may predict transformation by early detection of aggressive clones. Importantly, identical mutations can be linked to different clinical behaviors or risks of fibrotic progression and/or transformation in a context-dependent manner, i.e., MDS or MDS/MPN. Moreover, the order of mutational acquisition and the involved cell lineages matter. Several cases exemplify that histiocytic outgrowths in myeloid neoplasms are usually accompanied by a more aggressive clinical course and may be considered harbinger of disease progression. Exceptionally, lymphoblastic transformations can be seen. As best estimable, the histiocytic and lymphoblastic compounds in all occasions were clonally related to the myeloid compound and-where studied-displayed genomic alterations of, e.g., transcription factor genes or genes involved in MAPK signaling that might be mechanistically linked to the respective type of non-myeloid outgrowth.

Mutations associated with age-related clonal hematopoiesis in PMF patients with rapid progression to myelofibrosis

Besides histopathological findings there are no indicators of increased risk for fibrotic progression in myeloproliferative neoplasms (MPN). Age-related clonal hematopoiesis (ARCH/CHIP) is a frequent finding in the elderly and combinations with MPN driver mutations (JAK2, MPL, and CALR) have been described. To determine the impact of ARCH/CHIP-related mutations for development of fibrosis in primary myelofibrosis (PMF), the mutational status of cases with fibrotic progression from grade 0 to grade 2/3 (n = 77) as evidenced by follow-up bone marrow biopsies (median 6.2 years) was compared with prefibrotic PMF samples without development of fibrosis (n = 27; median follow-up 7.3 years). Frequent ARCH/CHIP-associated mutations (TET2, ASXL1, and DNMT3A) demonstrable at presentation were not connected with fibrotic progression. However, mutations which are rarely found in ARCH/CHIP (SRSF2, U2AF1, SF3B1, IDH1/2, and EZH2) were present in 24.7% of cases with later development of fibrosis and not detectable in cases staying free from fibrosis (P = 0.0028). Determination of the tumor mutational burden (TMB) in a subgroup of cases (n = 32) did not show significant differences (7.68 mutations/MB vs. 6.85 mutations/MB). We conclude that mutations rarely found in ARCH/CHIP provide an independent risk factor for rapid fibrotic progression (median 2.0 years) when manifest already at first presentation.

Genetic Testing in the Diagnosis and Biology of Acute Leukemia

OBJECTIVES

The 2017 Workshop of the Society for Hematopathology/European Association for Haematopathology examined the role of molecular genetics in the diagnosis and biology of acute leukemia.

METHODS

Acute leukemias were reviewed in two sessions: "Genetic Testing in Diagnosis of Acute Leukemias" (53 cases) and "Genetics Revealing the Biology of Acute Leukemias" (41 cases).

RESULTS

Cases included acute lymphoblastic leukemia, acute myeloid leukemia, and acute leukemia of ambiguous lineage. Many cases demonstrated genetic alterations of known diagnostic, prognostic, and/or therapeutic significance, while others exhibited alterations that illuminated disease biology. The workshop highlighted the complexity of acute leukemia diagnosis and follow-up, while illustrating advantages and pitfalls of molecular genetic testing.

CONCLUSIONS

Our understanding of the molecular genetics of acute leukemias continues to grow rapidly. Awareness of the potential complexity of genetic architecture and environment is critical and emphasizes the importance of integrating clinical information with morphologic, immunophenotypic, and molecular genetic evaluation.

How I treat the blast phase of Philadelphia chromosome–negative myeloproliferative neoplasms

The classic Philadelphia chromosome (Ph)–negative myeloproliferative neoplasms (MPNs) are a heterogeneous group of hematopoietic stem-cell diseases, characterized by activated JAK/STAT signaling and significant phenotypic mimicry, including a propensity for evolution to myeloid blast phase disease. Effective therapeutic options are limited for patients with Ph− MPNs in the blast phase (MPN-BP), and allogeneic stem-cell transplantation is the only known cure. Our increasing understanding of the molecular pathogenesis of this group of diseases, coupled with the increasing availability of targeted agents, has the potential to inform new subset-specific therapeutic approaches. Ultimately, progress in MPN-BP will hinge on prospective clinical and translational investigations with the goal of generating more effective treatment interventions. This case-based review highlights the molecular and clinical heterogeneities of MPN-BP and incorporates a treatment algorithm that underscores the importance of a personalized approach to this challenging group of diseases.

The Progress of Next Generation Sequencing in the Assessment of Myeloid Malignancies

The introduction and advances on next-generation sequencing have led to novel ways to integrate simultaneous assessment of multiple target genes in routine laboratory analysis. Assessment of myeloid neoplasms with targeted next-generation sequencing panels shows evidence to improve diagnosis, assist therapeutic decisions, provide better information about prognosis, and better detection of minimal residual disease. Herein, we provide information for application and utilization of next-generation sequencing studies with a focus on the most important mutations in acute myeloid leukemia, myelodysplastic syndrome, myeloproliferative neoplasms, and other myelodysplastic / myeloproliferative neoplasms in order to integrate them into the daily clinical practice.

How I treat myelofibrosis after failure of JAK inhibitors

The introduction of JAK inhibitors, leading to regulatory approval of ruxolitinib, represents a major therapeutic advance in myelofibrosis (MF). Most patients experience reduction in splenomegaly and improved quality of life from symptom improvement. It is a paradox, however, that, despite inhibition of signaling downstream of disease-related driver mutations, JAK inhibitor treatment is not associated with consistent molecular or pathologic responses in MF. Furthermore, there are important limitations to JAK inhibitor therapy including development of dose-limiting cytopenias and/or nonhematological toxicities such as neuropathy or opportunistic infections. Over half of the patients discontinue treatment within 3 years of starting treatment. Although data are sparse, clinical outcome after JAK inhibitor "failure" is likely poor; consequently, it is important to understand patterns of failure to select appropriate salvage treatment(s). An algorithmic approach, particularly one that incorporates cytogenetics/molecular data, is most helpful in selecting stem cell transplant candidates. Treatment of transplant-ineligible patients relies on a problem-based approach that includes use of investigational drugs, or consideration of splenectomy or radiotherapy. Data from early phase ruxolitinib combination studies, despite promising preclinical data, have not shown clear benefit over monotherapy thus far. Development of effective treatment strategies for MF patients failing JAK inhibitors remains a major unmet need.

Acute lymphoblastic leukemia secondary to myeloproliferative neoplasms or after lenalidomide exposure

Philadelphia‐negative (Ph⁻) myeloproliferative neoplasms (MPN) do rarely transform to acute lymphoblastic leukemia (ALL). While causality is difficult to establish, a few cases of ALL arising after exposure to lenalidomide for registered indications (multiple myeloma, myelodysplastic syndrome with 5q deletion) have been described in the literature.

Chronic Myelogenous Leukemia Presenting as a Secondary Malignancy After BCR-ABL1-negative B-lymphoblastic Leukemia/Lymphoma in a Pediatric Patient

Chronic myelogenous leukemia, BCR-ABL1 positive (CML) is a rare myeloproliferative neoplasm in children and presents even less often as a secondary malignancy in the pediatric population. Below, we report a patient with Philadelphia-negative B-lymphoblastic leukemia/lymphoma, who developed CML several years after achieving complete remission, and summarize the existing literature on the clinical and pathologic features of CML as a secondary pediatric malignancy.

Acute Lymphoblastic Leukemia Transformation in Polycythemia Vera: A Rare Phenomenon

Leukemic transformation in patients diagnosed with polycythemia vera (PV) is associated with poor prognosis and median survival not exceeding 3 months. To date only a few cases of post-PV acute lymphoblastic leukemia (ALL) have been reported. A 64-year-old female patient developed ALL 4 years after she had met PV criteria. At PV diagnosis a molecular study was positive for the JAK2V617F mutation. Due to high risk features (history of deep vein thrombosis) she was treated with hydroxyurea (HU) with moderate efficacy. She became anemic and thrombocytopenic with mild leukocytosis while still on HU. Blood and bone marrow smears revealed 40 and 100 % of blast cells, respectively. The immunophenotyping of blasts was consistent with a diagnosis of early precursor B cell ALL. She was found to be positive for the JAK2V617F mutation. Patient received an ALL induction regimen and achieved complete remission with negative minimal residual disease by flow cytometry. The post-chemotherapy study for the JAK2V617F mutation was positive. Patient has remained in remission for 4 months. A suitable donor searching was initiated. Post-PV ALL is an extremely rare phenomenon. Due to poor prognosis, an allogeneic stem cell transplantation should be considered in fit patients who achieved remission.

Acute Lymphoblastic Leukemia Arising in CALR Mutated Essential Thrombocythemia

The development of acute lymphoblastic leukemia in an existing myeloproliferative neoplasm is rare with historical cases unable to differentiate between concomitant malignancies or leukemic transformation. Molecular studies of coexisting JAK2 V617F-positive myeloproliferative neoplasms and mature B cell malignancies indicate distinct disease entities arising in myeloid and lymphoid committed hematopoietic progenitor cells, respectively. Mutations of CALR in essential thrombocythemia appear to be associated with a distinct phenotype and a lower risk of thrombosis yet their impact on disease progression is less well defined. The as yet undescribed scenario of pro-B cell acute lymphoblastic leukemia arising in CALR mutated essential thrombocythemia is presented. Intensive treatment for the leukemia allowed for expansion of the original CALR mutated clone. Whether CALR mutations in myeloproliferative neoplasms predispose to the acquisition of additional malignancies, particularly lymphoproliferative disorders, is not yet known.