Clinical characteristics and whole exome/transcriptome sequencing of coexisting chronic myeloid leukemia and myelofibrosis

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.

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.

Insights from a rare myeloproliferative neoplasm with coexisting BCR-ABL1 fusion gene, CALR, and TET2 mutations treated with nilotinib and ruxolitinib

Myeloproliferative neoplasms (MPNs) with concurrent BCR-ABL1 fusion gene and CALR mutation are especially rare. We report a patient with coexisting BCR-ABL1 fusion gene, CALR, and TET2 mutations who was treated with the combination of the second-generation TKI nilotinib and JAK1/JAK2 inhibitor ruxolitinib.

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.

Emergence of BCR-ABL1 Chronic Myeloid Leukemia in a JAK2-V617F Polycythemia Vera

Emergence of a new chronic myeloid neoplasm in the setting of a previous one, or their concomitant appearance seems to be a rare event, but plenty of cases have been reported. We describe the case of a patient with JAK2-V617F polycythemia vera, which looses JAK2 clone and develops overt BCR-ABL1 chronic myeloid leukemia after 6 years. Once treatment with tyrosine kinase inhibitors controls BCR-ABL1 clone, JAK2 clone arises again. In this report, we review the literature and discuss the clonal relationship of this event in light of the new molecular data.

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.

Coexisting driver mutations in MPN: clinical and molecular characteristics of a series of 11 patients

OBJECTIVES

CML, PV, ET and PMF are so called classical MPN with distinct clinical phenotypes. The discovery of the BCR-ABL1 translocation and mutations in driver genes JAK2, MPL and CALR has provided novel insights in their pathogenesis. While these mutations are thought to be mutually exclusive, rare cases of MPN with coexisting driver mutations have been reported. However, little is known about the clinical, biological and molecular characteristics of these patients and the interaction of the neoplastic clones.

METHODS

We retrospectively studied 11 MPN patients with coexisting driver mutations (JAK2 V617F + BCR-ABL1: n = 8; CALR type 2 + BCR-ABL1: n = 1; JAK2 V617F + MPL W515: n = 1; JAK2 V617F + CALR type 1: n = 1). To assess possible associated molecular aberrations, we analysed DNA of six patients using NGS.

RESULTS

In four CML patients, decreasing BCR-ABL1 transcript levels with increasing JAK2 V617F allele burden under TKI were observed. This strongly suggests that the coexistence of driver mutations originates from two different clones growing independently. Additional somatic mutations were detected in 5 out of 6 (83%) patients affecting 4 different genes, confirming the heterogeneity of this study cohort. Suboptimal response to TKI was observed with a higher frequency (4/8 patients) than reported in conventional series of CML and the overall tolerance of treatment with hydroxyurea and/or imatinib in our series was poor.

CONCLUSION

Given the emergence of NGS in clinical practice, more similar cases will be identified in the coming years. The optimal treatment strategy for this rare group of patients is uncertain and toxicity of combination treatment may have to be considered.