Myeloproliferative neoplasms with concurrent BCR-ABL1 translocation and JAK2 V617F mutation: a multi-institutional study from the bone marrow pathology group

Association of JAK2V617F allele burden and clinical correlates in polycythemia vera: a systematic review and meta-analysis

Janus kinase 2 (JAK2) V617F mutation is present in most patients with polycythemia vera (PV). One persistently puzzling aspect unresolved is the association between JAK2V617F allele burden (also known as variant allele frequency) and the relevant clinical characteristics. Numerous studies have reported associations between allele burden and both hematologic and clinical features. While there are strong indications linking high allele burden in PV patients with symptoms and clinical characteristics, not all associations are definitive, and disparate and contradictory findings have been reported. Hence, this study aimed to synthesize existing data from the literature to better understand the association between JAK2V617F allele burden and relevant clinical correlates. Out of the 1,851 studies identified, 39 studies provided evidence related to the association between JAK2V617F allele burden and clinical correlates, and 21 studies were included in meta-analyses. Meta-analyses of correlation demonstrated that leucocyte and erythrocyte counts were significantly and positively correlated with JAK2V617F allele burden, whereas platelet count was not. Meta-analyses of standardized mean difference demonstrated that leucocyte and hematocrit were significantly higher in patients with higher JAK2V617F allele burden, whereas platelet count was significantly lower. Meta-analyses of odds ratio demonstrated that patients who had higher JAK2V617F allele burden had a significantly greater odds ratio for developing pruritus, splenomegaly, thrombosis, myelofibrosis, and acute myeloid leukemia. Our study integrates data from approximately 5,462 patients, contributing insights into the association between JAK2V617F allele burden and various hematological parameters, symptomatic manifestations, and complications. However, varied methods of data presentation and statistical analyses prevented the execution of high-quality meta-analyses.

Chronic myeloproliferative neoplasms with concomitant CALR mutation and BCR::ABL1 translocation: diagnostic and therapeutic implications of a rare hybrid disease

Myeloproliferative neoplasms (MPNs) are subdivided into Philadelphia (Ph) chromosome-positive chronic myeloid leukemia (CML) and Ph-negative MPNs. BCR::ABL1 translocation is essential for the development and diagnosis of CML; on the other hand, the majority of Ph-negative MPNs are characterized by generally mutually exclusive mutations of Janus kinase 2 (JAK2), calreticulin (CALR), or thrombopoietin receptor/myeloproliferative leukemia (MPL). CALR mutations have been described essentially in JAK2 and MPL wild-type essential thrombocythemia and primary myelofibrosis. Rarely coexisting CALR and MPL mutations have been found in Ph-negative MPNs. BCR::ABL1 translocation and JAK2 mutations were initially considered mutually exclusive genomic events, but a discrete number of cases with the combination of these genetic alterations have been reported. The presence of BCR::ABL1 translocation with a coexisting CALR mutation is even more uncommon. Herein, starting from a routinely diagnosed case of CALR-mutated primary myelofibrosis subsequently acquiring BCR::ABL1 translocation, we performed a comprehensive review of the literature, discussing the clinicopathologic and molecular features, as well as the outcome and treatment of cases with BCR::ABL1 and CALR co-occurrence.

From primary myelofibrosis to chronic myeloid leukemia, BCR::ABL1+ B-Lymphoblastic leukemia, and back to primary myelofibrosis: An illustration of dynamic clonal evolution

The simultaneous detection of BCR::ABL1 and JAK2 V617F was rarely reported and their clonal relationship and dynamic clonal shift were not characterized. Here, we described a unique case with the initial presentation as JAK2 V617F+ primary myelofibrosis, followed by the emergence of BCR::ABL1+ chronic myeloid leukemia. The patient then developed BCR::ABL1+ B-lymphoblastic leukemia. Treatment for B-lymphoblastic leukemia prompted a regression to the state of primary myelofibrosis. In light of these observations, we proposed a clonal evolution model for this case.

Co-occurrence of JAK2-V617 F mutation and BCR::ABL1 translocation in chronic myeloproliferative neoplasms: a potentially confounding genetic combination

Myeloproliferative neoplasms (MPNs) are classified into Philadelphia (Ph) chromosome-positive chronic myeloid leukemia (CML) and Ph-negative MPNs. BCR::ABL1 translocation is the key genetic event of CML, whereas JAK2/MPL/CALR mutations are molecular aberrations of Ph-negative MPNs. Despite initially considered mutually exclusive genetic aberrations, the co-occurrence of BCR::ABL1 and JAK2 has been reported in a limited number of cases. The two genetic alterations may be identified either at the same time or JAK2 aberration may be detected in patients with a previous CML treated with tyrosine kinase inhibitors or, finally, BCR::ABL1 translocation occurs in patients with a history of JAK2-positive MPN. This combination of genomic alterations is potentially confounding with clinical manifestations often misinterpreted either as disease progression or drug resistance, therefore leading to inappropriate patient's treatment. Our systematic review aims to improve hematologist and pathologist knowledge on this rare subset of patients. Starting from the presentation of two additional cases from our routine daily practice, we focus mainly on clinical, laboratory, and bone marrow histological findings, which may represent useful clues of BCR::ABL1 and JAK2 co-occurrence. The interaction between JAK2 and BCR::ABL1 clones during the disease course as well as therapy and outcome are presented.

A customized mass array panel for BCR::ABL1 tyrosine kinase domain mutation screening in chronic myeloid leukemia

Introduction

The therapeutic strategy and management of chronic myeloid leukemia (CML) have rapidly improved with the discovery of effective tyrosine kinase inhibitors (TKIs) to target BCR::ABL1 oncoprotein. However, nearly 30% of patients develop TKI resistance due to acquired mutations on the tyrosine kinase domain (TKD) of BCR::ABL1.

Methods

We customized a mass array panel initially intended to detect and monitor the mutational burden of hotspot BCR::ABL1 TKD mutations accumulated in our database, including key mutations recently recommended by European LeukemiaNet. Additionally, we extended the feasibility of using the assay panel for the molecular classification of myeloproliferative neoplasms (MPNs) by incorporating primer sets specific for analyzing JAK2 V617F, MPL 515 K/L, and CALR types 1 and 2.

Results

We found that the developed mass array panel was superior for detecting and monitoring clinically significant BCR::ABL1 TKD mutations, especially in cases with low mutational burden and harboring compound/polyclonal mutations, compared with direct sequencing. Moreover, our customized mass array panel detected common genetic alterations in MPNs, and the findings were consistent with those of other comparable assays available in our laboratory.

Conclusions

Our customized mass array panel was practicably used as a routine robust assay for screening and monitoring BCR::ABL1 TKD mutations in patients with CML undergoing TKI treatment and feasible for analyzing common genetic mutations in MPNs.

Cytological Diagnosis of Classic Myeloproliferative Neoplasms at the Age of Molecular Biology

Myeloproliferative neoplasms (MPN) are clonal hematopoietic stem cell-derived disorders characterized by uncontrolled proliferation of differentiated myeloid cells. Two main groups of MPN, BCR::ABL1-positive (Chronic Myeloid Leukemia) and BCR::ABL1-negative (Polycythemia Vera, Essential Thrombocytosis, Primary Myelofibrosis) are distinguished. For many years, cytomorphologic and histologic features were the only proof of MPN and attempted to distinguish the different entities of the subgroup BCR::ABL1-negative MPN. World Health Organization (WHO) classification of myeloid neoplasms evolves over the years and increasingly considers molecular abnormalities to prove the clonal hematopoiesis. In addition to morphological clues, the detection of JAK2, MPL and CALR mutations are considered driver events belonging to the major diagnostic criteria of BCR::ABL1-negative MPN. This highlights the preponderant place of molecular features in the MPN diagnosis. Moreover, the advent of next-generation sequencing (NGS) allowed the identification of additional somatic mutations involved in clonal hematopoiesis and playing a role in the prognosis of MPN. Nowadays, careful cytomorphology and molecular biology are inseparable and complementary to provide a specific diagnosis and to permit the best follow-up of these diseases.

A 68-Year-Old Man with a Cytogenetic Diagnosis of Chronic Myeloid Leukemia and Bone Marrow Findings of Philadelphia Chromosome Translocation Between the Long Arm of Chromosomes 9 and 22, Leading to the BCR-ABL1 Fusion Gene and V617F Mutation in the JAK2 Gene

BACKGROUND Breakpoint cluster region (BCR)-Abelson murine leukemia (ABL1) and Janus Kinase-2 (JAK2) mutations have been thought to be mutually exclusive in myeloproliferative neoplasms (MNPs), but recent data suggest that they can occur together. CASE REPORT A 68-year-old man was referred to the hematology clinic because of an elevated white blood cell count. His medical history included type II diabetes mellitus, hypertension, and retinal hemorrhage. Fluorescence in situ hybridization analysis of the bone marrow was positive for BCR-ABL1 in 66/100 cells. Conventional cytogenetics was positive for the Philadelphia chromosome in 16/20 counted cells. The percentage of BCR-ABL1 was 12%. Considering the patient's age and medical comorbidities, he was started on imatinib 400 mg once daily. Further tests showed JAK2 V617F mutation positivity and absence of acquired von Willebrand disease. He was then started on aspirin 81 mg and hydroxyurea 500 mg once daily, which was later increased to 1000 mg daily. The patient achieved a major molecular response after 6 months of treatment, with undetectable BCR-ABL1 levels. CONCLUSIONS BCR-ABL1 and JAK2 mutations can co-existence in MNPs. Physicians must suspect the presence of one of the MPNs in chronic myeloid leukemia (CML) patients with persistent or increased thrombocytosis, an atypical course of the disease, or hematological abnormalities despite evidence of response or remission of CML. Therefore, testing for JAK2 should be performed accordingly. Combining cytoreductive therapy with tyrosine kinase inhibitors (TKIs) is a therapeutic option when both mutations are present, and TKI alone is not sufficient to control peripheral blood cell counts.

Chronic myeloid leukemia (CML) evolves from Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs) with unexpected frequency

Myeloproliferative neoplasms (MPN) are chronic clonal disorders characterized by overproduction of myeloid-lineage blood cells and potential risk of evolution to acute myeloid leukemia (AML). Chronic myeloid leukemia (CML) is distinct from other MPNs in that its pathophysiology stems from the BCR-ABL fusion protein of the Philadelphia chromosome (Ph +). Though there are known cases of Ph- and Ph + MPNs coexisting in a single patient, overall prevalence has never been quantified in a prospective cohort. Here, we review our center's MPN registry, which shows 0.6% of Ph- MPN patients later developed CML. This development occurred no less than 10 and up to 36 years after Ph- MPN diagnosis. This rate of chronic transformation exceeds what is expected, as the incidence of CML in the United States is 2 per 100,000 people-years. The probability of this CML case rate in an average-risk population is less than 0.001%, suggesting there are shared risk factors between Ph- and Ph + MPNs. We speculate that these risk factors may include exposures, genetic predispositions, or be inherent to disease biology. Abrupt-onset leukocytosis heralded post-MPN CML in all cases here and suggests this salient clinical feature should trigger hematologists to consider this diagnosis and perform appropriate testing.

Long-Term Molecular Remission after Treatment with Imatinib in a Chronic Myeloid Leukemia Patient with Extreme Thrombocytosis Harboring Rare e14a3 (b3a3) BCR::ABL1 Transcript: A Case Report

An atypical BCR::ABL1 fusion gene transcript in chronic myeloid leukemia (CML) patients, even those with variant Philadelphia (Ph) chromosome translocation, is very rare. In the present study, we report a case of CML (41 years, female) with extreme thrombocytosis at onset, with the variant Ph chromosome and rare e14a3 (b3a3) BCR::ABL1 transcript. The patient was prescribed imatinib as a first-line therapy and subsequently achieved complete hematologic remission within 2 months and major molecular response (MMR) within 3 months, and the transcript was undetectable within half a year. During up to nine years of follow-up, the quantification of this rare fusion gene was consistently negative with no BCR::ABL1 kinase domain mutations. Furthermore, we collected previously reported CML cases with the e14a3 (b3a3) transcript that indicated that the e14a3 (b3a3) transcripts appeared to have a larger number of thrombocytosis and variant Ph translocations than CML in general. This subgroup of CML might have better responses and outcomes to imatinib than patients with common transcripts.

BCR-ABL1 is a secondary event after JAK2V617F in a patient with essential thrombocythemia who develop chronic myeloid leukemia

Several cases such as myeloproliferative neoplasms (MPN) with the coexistence of JAK2 and BCR-ABL have been reported. However, cases of transformation of essential thrombocythemia (ET) into chronic myeloid leukemia (CML) during the disease progression were rarely reported. Here, we report the case of a patient with JAK2 V617F- positive ET who subsequently acquired BCR-ABL1, which transformed the disease into CML after 10 years from the initial diagnosis. In this study, we dynamically monitored JAK2 V617F and BCR-ABL and observed multiple gene mutations, including IDH2, IDH1, ASXL1, KRAS, and RUNX1. It is important to be aware of this potentially clone evolution in disease progression.

Is Allogeneic Transplantation an Option in Patients Affected by Concurrent Myelofibrosis and Chronic Myeloid Leukemia (CML)?

Classification of myeloproliferative neoplasms is based on hematologic, histopathologic, and molecular characteristics, including the BCR-ABL1 and JAK2 V617F or MPL and CALR. Although the different gene mutations ought to be mutually exclusive, several cases with co-occurring BCR-ABL1 and JAK2 V617F or CALR have been identified with a frequency of 0.2–2.5% in the European population. The tyrosine kinase abnormalities appeared to affect independent subclones because imatinib mesylate (IM) treatment induced Ph+-CML remission, whereas the JAK2V617F clone either persisted or clinically expanded after a major response of Ph+-clone.

Allogeneic stem cell transplantation is at present the only potentially curative therapy for these patients after therapy with ruxolitinib and TKI inhibitor. We describe the case of 3 young people treated in our institution for the coexistence of BCR/ABL chronic myeloid leukemia and another Philadelphia chromosome-negative (Ph−) Chronic myeloproliferative disease. They received ruxolitinib, imatinib/nilotinib, and allogeneic transplantation with safe and efficient results.

Sequential Development of JAK2V617F Mutation and BCR-ABL1 Fusion in Individual Patients With Myeloproliferative Neoplasms: A Linear Clonal Evolution or Parallel Clonal Competition?

CONTEXT.—

Concomitant BCR-ABL1 and JAK2V617F in myeloproliferative neoplasms (MPNs) is rare, and its pathogenesis and clinical significance are unclear.

OBJECTIVE.—

To investigate the clonal relationship between the 2 genomic alterations, as well as the clinicopathologic impact.

DESIGN.—

Retrospective analysis of MPNs with sequential development of BCR-ABL1 and JAK2V617F.

RESULTS.—

Of 6 cases, 5 had JAK2V617F-positive MPN diagnosed before acquiring BCR-ABL1 years later, and 1 had BCR-ABL1+ chronic myeloid leukemia before JAK2V617F-positive myelofibrosis completely replaced the BCR-ABL1+ clone 1 year after tyrosine kinase inhibitor therapy. Among the former group, treatment for the initial MPN involved hydroxyurea, ruxolitinib, and/or supportive care, and the latency to the development of JAK2V617F ranged from 4 to 13 years (median of 9 years). Four cases showed retention of JAK2V617F, whereas BCR-ABL1 emerged as the major clone, including 2 that exhibited parallel increases in JAK2V617F and BCR-ABL1 burdens, with both genomic markers exceeding 50%. Three patients received stem cell transplants and demonstrated sustained engraftment, with the genomic markers below detectable levels.

CONCLUSIONS.—

Most MPNs with concomitant JAK2V617F and BCR-ABL1 are actually composite MPNs with a "second hit" residing on a different clone. Rare cases demonstrate a subclone harboring a "double-hit" in a background of a JAK2V617F-positive stem line clone. The probability of a "double-hit" with a BCR-ABL1+ stem line clone is probably reduced by effective tyrosine kinase inhibitor treatment. The treatment often involves combined kinase inhibitors and/or hydroxyurea, but the outcome is unpredictable; hematopoietic stem cell transplantation may be the ultimate therapeutic option for this complicated disease.

Synoptic Diagnostics of Myeloproliferative Neoplasms: Morphology and Molecular Genetics

Simple Summary

The diagnosis of myeloproliferative neoplasms requires assessment of a combination of clinical, morphological, immunophenotypic and genetic features, and this integrated, multimodal approach forms the basis for precise classification. Evaluation includes cell counts and morphology in the peripheral blood, bone marrow aspiration and trephine biopsy, and may encompass flow cytometry for specific questions. Diagnosis nowadays is completed by targeted molecular analysis for the detection of recurrent driver and, optionally, disease-modifying mutations. According to the current World Health Organization classification, all myeloproliferative disorders require assessment of molecular features to support the diagnosis or confirm a molecularly defined entity. This requires a structured molecular analysis workflow tailored for a rapid and cost-effective diagnosis. The review focuses on the morphological and molecular features of Ph-negative myeloproliferative neoplasms and their differential diagnoses, addresses open questions of classification, and emphasizes the enduring role of histopathological assessment in the molecular era.

Abstract

The diagnosis of a myeloid neoplasm relies on a combination of clinical, morphological, immunophenotypic and genetic features, and an integrated, multimodality approach is needed for precise classification. The basic diagnostics of myeloid neoplasms still rely on cell counts and morphology of peripheral blood and bone marrow aspirate, flow cytometry, cytogenetics and bone marrow trephine biopsy, but particularly in the setting of Ph− myeloproliferative neoplasms (MPN), the trephine biopsy has a crucial role. Nowadays, molecular studies are of great importance in confirming or refining a diagnosis and providing prognostic information. All myeloid neoplasms of chronic evolution included in this review, nowadays feature the presence or absence of specific genetic markers in their diagnostic criteria according to the current WHO classification, underlining the importance of molecular studies. Crucial differential diagnoses of Ph− MPN are the category of myeloid/lymphoid neoplasms with eosinophilia and gene rearrangement of PDGFRA, PDGFRB or FGFR1, or with PCM1-JAK2, and myelodysplastic/myeloproliferative neoplasms (MDS/MPN). This review focuses on morphological, immunophenotypical and molecular features of BCR-ABL1-negative MPN and their differential diagnoses. Furthermore, areas of difficulties and open questions in their classification are addressed, and the persistent role of morphology in the area of molecular medicine is discussed.

Successful Treatment of a Patient with Chronic Myelogenous Leukemia with Concurrent Janus Kinase 2 (JAK2) R795S Mutation and Breakpoint Cluster Region-ABL1 (BCR-ABL1) Fusion: A Case Report and Literature Review

Patient: Female, 50-year-old

Final Diagnosis: Chronic myeloid leukaemia

Symptoms: Dizziness • weakness

Medication: —

Clinical Procedure: —

Specialty: Hematology

Co-existence of mutations in myeloproliferative neoplasms and their clinical significance: a prognostic approach

OBJECTIVE

Myeloproliferative neoplasms (MPNs) are a group of clonal hematopoietic stem cell disorders that may occur after one or more mutations in hematopoietic progenitor cells. In this study, we will review the co-existence of mutations (especially dual mutations) in MPNs and its effect on the prognosis of patients.

METHODS

To find relevant published papers, we systematically searched six major international indexing databases, namely PubMed/Medline, EmBase, Cochrane central, ISI web of science, and Scopus from Feb. 2000 until Jan. 2020. We included the following keywords in the analyzes: Myeloproliferative Disorders, Mutation, Co-existence of Mutations, Acute myeloid leukemia.

RESULTS

Co-existence of several mutations in MPNs is mainly associated with a poor prognosis compared with the unimutated MPN disorders. There are several effective factors such as sequence of mutations, incidence of mutations in one cell or different cells, mutation, and MPN type.

CONCLUSION AND EXPERT COMMENTARY

It seems that monitoring the status of mutations in MPNs and recognizing the co-existence of mutations (especially dual mutations) in order to determine prognosis and possibility of progression to acute form of leukemia can lead to the prediction of prognosis in MPN patients as well as establishment of better and more reliable therapeutic strategies for patients.

Atypical myeloproliferative neoplasm with concurrent BCR-ABL1 fusion and CALR mutation: A case report and literature review

RATIONALE

Concurrent calreticulin (CALR) mutation and BCR-ABL1 fusion are extremely rare in chronic myelogenous leukemia; to date, only 12 cases have been reported.

PATIENT CONCERNS

A 57-year-old male who had an 11-year history of essential thrombocytosis presented to our hospital with leukocytosis and marked splenomegaly for 3 months.

DIAGNOSES

Chronic myelogenous leukemia with myeloid fibrosis arising on the background of essential thrombocytosis harboring both BCR-ABL1 fusion and type-1 like CALR mutation.

INTERVENTIONS

Imatinib was started at 300 mg daily and increased to 400 mg daily after 3 months; interferon was added after 12 months.

OUTCOMES

Partial cytogenetic response was achieved after 3 months of imatinib therapy and complete cytogenetic response was achieved after 1 year of treatment. However, CALR mutation was still present with a stable mutational allele burden.

LESSONS

In this case report and review of additional 12 cases with simultaneous presence of CALR-mutation and BCR-ABL1 fusion, we highlighted the importance of integrating clinical, morphological, and molecular genetic data for classifying atypical myeloid neoplasms.

Genetic Testing in the Diagnosis and Biology of Myeloid Neoplasms (Excluding Acute Leukemias)

OBJECTIVES

The 2017 Workshop of the Society for Hematopathology/European Association for Haematopathology reviewed the role of genetic testing in the diagnosis of hematopoietic neoplasms, including non-acute leukemia myeloid malignancies.

METHODS

The workshop panel assigned 98 submitted cases to the category of non-acute leukemia myeloid neoplasms, of which 13 were selected for oral presentation.

RESULTS

Data from both conventional karyotyping and genetic sequencing had important impact on diagnosis, classification, and prognostication. However, some cases had genetic results that appeared discordant from the morphology and/or clinical features. Thus, the workshop underscored the need for careful management of genetic data by the pathologist and clinician, in the context of other findings.

CONCLUSIONS

The workshop cases highlighted the significance of genetic aberrations in the diagnosis and treatment of non-acute leukemia myeloid neoplasms. Many genetic data have already been incorporated in the most recent World Health Organization classification, and undoubtedly they will factor increasingly in future classifications.

Chronic Myeloid Leukemia: Beyond BCR-ABL1

PURPOSE OF REVIEW

In this review, we emphasize up-to-date practical cytogenetic and molecular aspects of chronic myeloid leukemia (CML) and summarize current knowledge on tyrosine kinase inhibitor (TKI) resistance and treatment response monitoring of CML.

RECENT FINDINGS

The introduction of TKIs has changed the natural course of CML and markedly improved patient survival. Over the past decades, many research efforts were devoted to elucidating the leukemogenic mechanisms of BCR-ABL1 and developing novel TKIs. More recent studies have attempted to answer new questions that have emerged in the TKI era, such as the cytogenetic and molecular bases of treatment failure and disease progression, the clinical impact of genetic aberrations in Philadelphia chromosome (Ph)-positive and Ph-negative cells, and the biological significance of Ph secondarily acquired during therapy of other hematological neoplasms. Recent progresses in the understanding of the cytogenetic and molecular mechanisms underlying therapeutic failure and disease progression have improved the risk stratification of CML and will be helpful in the design of novel therapeutic strategies.

Colony-Forming Cell Assay Detecting the Co-Expression of JAK2V617F and BCR-ABL1 in the Same Clone: A Case Report

BCR-ABL1-negative myeloproliferative disorders and chronic myeloid leukaemia are haematologic malignancies characterised by single and mutually exclusive genetic alterations. Nevertheless, several patients co-expressing the JAK2V617F mutation and the BCR-ABL1 transcript have been described in the literature. We report the case of a 61-year-old male who presented with an essential thrombocythaemia phenotype and had a subsequent diagnosis of chronic phase chronic myeloid leukaemia. Colony-forming assays demonstrated the coexistence of 2 different haematopoietic clones: one was positive for the JAK2V617F mutation and the other co-expressed both JAK2V617F and the BCR-ABL1 fusion gene. No colonies displayed the BCR-ABL1 transcript alone. These findings indicate that the JAK2V617F mutation was the founding genetic alteration of the disease, followed by the acquisition of the BCR-ABL1 chimeric oncogene. Our data support the hypothesis that a heterozygous JAK2V617F clone may have favoured the bi-clonal nature of this myeloproliferative disorder, generating clones harbouring a second transforming genetic event.

Unique Case of Myeloproliferative Neoplasm with Two Rare Clonal Abnormalities: Rare JAK2 Exon 12 Mutation and Rare e14a3 (b3a3) BCR/ABL Fusion Transcript

Myeloproliferative neoplasms (MPNs) are clonal disorders divided into Philadelphia (Ph) chromosome-positive chronic myeloid leukemia (CML) or Ph chromosome-negative MPNs. Co-occurrence of these disease entities is very rare and typically involves presence of common p190 or p210 BCR/ABL fusion transcript (responsible for CML) along with JAK2V617F mutation (most common driver mutation in Ph-negative MPNs). Because of the rarity of such cases, it is not clear if the outcomes are any different in these patients. In this article, we report a unique patient with polycythemia vera driven by a rare complex in-frame deletion-insertion mutation in JAK2 exon 12, and CML driven by uncommon p210 e14a3 (b3a3) BCR/ABL fusion transcript. We describe clinical and laboratory features, bone marrow pathology, treatment, and overall outcome.