Translocation (9;12)(q34.1;p13.?3) Resulted in ETV6-ABL1 Fusion in a Patient with Philadelphia Chromosome-Negative Chronic Myelogenous Leukemia

Complex Genomic Rearrangements Involving ETV6::ABL1 Gene Fusion in an Individual with Myeloid Neoplasm

ETV6::ABL1 gene fusion is a rare recurrent genomic rearrangement associated with hematologic malignancies, and frequently occurs with additional anomalies. Due to the opposite chromosome orientations of the ETV6 and ABL1 genes, an oncogenic in-frame ETV6::ABL1 gene fusion cannot be formed by a simple translocation. The molecular mechanism of the ETV6::ABL1 fusion and the significance of co-occurring anomalies are not fully understood. We characterized genomic alterations in an individual with ETV6::ABL1 gene-fusion-positive myeloid neoplasm using various genomic technologies. Our findings uncovered a molecular mechanism of the ETV6::ABL1 fusion, in which a paracentric inversion within the short arm of chromosome 12 (12p) and a translocation between the long arm of a chromosome 9 and the 12p with the inversion were involved. In addition, we detected multiple additional anomalies in the individual, and our findings suggested that the ETV6::ABL1 fusion occurred as a secondary event in a subset of cells with the additional anomalies. We speculate that the additional anomalies may predispose to further pathogenic changes, including ETV6::ABL1 fusion, leading to neoplastic transformation.

Cryptic ETV6-ABL1 Fusion and MLL2 Truncation Revealed by Integrative Clinical Sequencing in Multiply Relapsed Acute Lymphoblastic Leukemia

The ETV6-ABL1 fusion is a rare genetic aberration classified as Philadelphia chromosome-like high-risk B-cell precursor acute lymphoblastic leukemia. We present the case of a child with multiply relapsed B-cell precursor acute lymphoblastic leukemia in which next-generation sequencing identified this cryptic fusion, undetected by standard testing, resulting in sustained clinical response to targetted therapy with imatinib. Upon subsequent relapse, repeat next-generation sequencing identified an additional aberration, MLL2-ADCY9, as a possible molecular driver conferring resistance to therapy. This report demonstrates the exciting potential of integrative clinical sequencing in identifying previously undetected actionable findings leading to improved outcomes in pediatric oncology patients.

Myeloproliferative neoplasm with ABL1/ETV6 rearrangement mimics chronic myeloid leukemia and responds to tyrosine kinase inhibitors

Myeloproliferative neoplasms (MPN) associated with ABL1-ETV6 fusions are rare and poorly characterized. To date, less than 20 cases of ABL1-ETV6+ MPN have been reported. We report a 47-year-old man who presented with MPN with clinicopathologic features resembling chronic myeloid leukemia, but there was no evidence of t(9;22)(p34.1;q11.2) or BCR-ABL1 fusion. Conventional cytogenetics and fluorescence in situ hybridization analysis showed ins(12;9)(p13;q34q34) that led to ETV6-ABL1 fusion. The patient responded well to tyrosine kinase inhibitor therapy and achieved remission for 7 years.