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

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.

Genetic and Clinical Characteristics of Patients with Philadelphia-Negative Myeloproliferative Neoplasm Carrying Concurrent Mutations in JAK2V617F, CALR, and MPL

Simultaneous mutations in Janus kinase 2 (JAK2), calreticulin, and myeloproliferative leukemia (MPL) genes are generally not considered for characterizing Philadelphia-negative myeloproliferative neoplasms (MPNs), leading to misdiagnosis. Sanger sequencing and quantitative polymerase chain reaction were used to detect gene mutations in patients with MPN. We retrospectively screened the data of patients with double mutations in our center and from the PubMed database. Two patients tested positive for both JAK2V617F and CALR mutations (2/352 0.57%) in our center, while data of 35 patients from the PubMed database, including 26 patients with essential thrombocythemia (ET), 6 with primary myelofibrosis (PMF), 2 with unexplained thrombosis, and 1 with polycythemia vera were screened for double mutations. Among these mutations, co-mutation of JAKV617F-CALR constituted the majority (80.0%), when compared with JAKV617F-MPL (17.1%) and CALR-MPL (2.9%) mutations. Moreover, patients with concurrent mutational myeloproliferative neoplasm (MPN) were relatively older (P  =  .010) with significantly higher platelet counts than their counterparts with single gene mutations (P < .001). The occurrence of palpable splenomegaly (P < .001) and leukocyte count (P  =  .041) were also significantly different between patients with single and simultaneous gene mutations. These 4 risk factors also showed significant test effectiveness in the ET and PMF cohorts (P < .05). In terms of clinical characteristics of patients with ET, those with JAK2V617F-CALR mutation had higher but normal hemoglobin levels (P  =  .0151) than those carrying JAK2V617F-MPL mutation. From a clinical perspective, patients with multiple mutational MPN are different from those with single gene mutations. The poor treatment response by patients in our center and unfavorable indicators for patients with co-mutations in published literature indicate that customized treatment may be the best choice for patients with MPN carrying co-mutations.

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.

A Rare Co-Occurrence of Triple Mutations in JAK2, CALR, and MPL in the Same Patient with Myelofibrosis

Background. The diagnosis and prognostication of myeloproliferative neoplasm rely on the presence of driver mutations in JAK2, calreticulin (CALR), and MPL mutations. In the past, the presence of these mutations was thought to be mutually exclusive. Since then, there have been multiple reports of the presence of dual mutations. The presence of all three driver mutations in the same patient with myelofibrosis has not been previously described. Case. A 73-year-old female underwent a hematological workup in our facility after a routine hemogram performed prior to complex ophthalmological surgery revealed severe thrombocytosis. A comprehensive workup including an NGS panel for MPN driver mutations demonstrated that she had a calreticulin type-1 mutation, a JAK2 exon 14 (JAK2L611S) mutation, and an abnormal hotspot variant for MPL with VAF1%. A bone marrow biopsy confirmed a myeloproliferative neoplasm with grade 2 reticulin fibrosis suggesting primary myelofibrosis. Molecular profiling of bone marrow confirmed the previously noted mutations and an MPLW515R mutation. The patient was started on treatment with hydroxyurea and aspirin with improvement in platelet count and resolution of anemia. Discussion. The clinical significance of the presence of multiple driver mutations in the same patient is not well understood at this time. There have been 11 publications between 2014 and 2020 that have described dual mutations of JAK2V617F, MPL, and CALR mutations. The JAK2 exon 14 mutation noted, in this case, is JAK2L611S which has not previously been reported in MPN and only reported in 5 cases in the COSMIC database. The JAK2 exon 14 mutation identified in this case is not an established driver mutation for myeloproliferative neoplasm, and its clinical implication remains unknown. Conclusions. The above case in addition to recent case reports and case series supports the use of broader NGS sequencing panels for diagnosis and prognostication of MPN. These mutations should not be considered mutually exclusive. The clinical behavior and prognosis of the subgroup with multiple mutations need to be studied in larger series.

Co-existence of BCR-ABL and JAK2V617F mutation in resistant chronic myeloid leukemia in the imatinib era: Is there a correlation?

INTRODUCTION

Diagnoses of myeloproliferative disorder is based on molecular marker. Chronic Myeloid Leukemia and Myeloproliferative neoplasms were considered mutually exclusive and co-existence of BCR/ABL1 and JAK2 mutation is a rare phenomenon.

CASE REPORT

Here, we present two cases of co-existence of BCR-ABL and JAK2V617F positivity. We characterize the course of the disease, mainly the minimal residual disease.Management and outcome: The two cases was initially managed as Chronic Myeloid Leukemia and treated by TKI inhibitors. The first one was diagnosed in 2010. He started the first line of TKI, and then switched to second line without obtaining a major molecular response. Hence he was tested for JAK2V617F mutation and positivity was diagnosed. The second patient showed Chronic Myeloid Leukemia phenotype with coexistence of BCR/ABL1 and JAK2 mutation at diagnosis. Molecular monitoring reveals a high BCR-ABL1 transcript level (20%) at the last follow-up (12 months).

DISCUSSION

Ours results highlight that JAK2V617F/BCR-ABL double positivity may be a potential marker of resistance in Chronic Myeloid Leukemia and clonal molecular analysis is mandatory to elucidate the mechanism. Moreover, the combination of JAK and TKI inhibitors might be effective and potentially be guided by molecular monitoring of minimal residual disease.

A Rare Case of Essential Thrombocythemia with Coexisting JAK2 and MPL Driver Mutations

Philadelphia-negative (Ph-) classical myeloproliferative neoplasms (MPNs) include polycythemia vera, essential thrombocythemia (ET), and primary myelofibrosis. Somatic driver mutations in the JAK2, CALR, and MPL genes serve as major diagnostic criteria of the Ph- MPNs and these mutations occur in a mutually exclusive manner. In this report, we describe the first case of ET harboring double mutations in JAK2 V617F and MPL. For MPL, the patient had multiple clones of MPL mutations: c.1543_1546delinsAGGG (p.Trp515_Gln516delinsArgGlu) and c.1546C>G (p.Gln516Glu). The JAK2 V617F allele burden in our patient is very low (4%) compared to the relatively high (17%-78%) allele frequency of MPL mutations. The low JAK2 mutant burden might be explained by preexisting clonal hematopoiesis before overt signs of MPNs, followed by the acquisition of a second oncogenic mutation of CALR or MPL leading to the MPN phenotype. This highlights that screening for a second driver mutation should be considered in patients with a low JAK2 mutant burden by reporting a 57-year-old Korean man with ET.

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.

Coexistence of breakpoint cluster region-Abelson1 rearrangement and Janus kinase 2 V617F mutation in chronic myeloid leukemia: A case report

BACKGROUND

The Janus kinase 2 (JAK2) V617F mutation is common in patients with breakpoint cluster region-Abelson1 (BCR-ABL1)-negative myeloproliferative neoplasms, including polycythemia vera, essential thrombocythemia and primary myelofibrosis, but is rarely detected in BCR-ABL1-positive chronic myeloid leukemia (CML) patients. Here, we report a CML patient with both a BCR-ABL1 rearrangement and JAK2 V617F mutation.

CASE SUMMARY

A 45-year-old Chinese woman was admitted to our department with a history of significant thrombocytosis for 20 d. Color Doppler ultrasound examination showed mild splenomegaly. Bone marrow aspiration revealed a karyotype of 46, XX, t(9;22)(q34;q11.2) in 20/20 metaphases by cytogenetic analysis, rearrangement of BCR-ABL1 (32.31%) by fluorescent polymerase chain reaction (PCR) and mutation of JAK2 V617F (10%) by PCR and Sanger DNA sequencing. The patient was diagnosed with CML and JAK2 V617F mutation. Following treatment with imatinib for 3 mo, the patient had an optimal response and BCR-ABL1 (IS) was 0.143%, while the mutation rate of JAK2 V617F rose to 15%.

CONCLUSION

Emphasis should be placed on the detection of JAK2 mutation when CML is diagnosed to distinguish JAK2 mutation-positive CML and formulate treatment strategies.