Chronic eosinophilic leukemia, NOS with t(5;12)(q31;p13)/ETV6-ACSL6 gene fusion: A novel variant of myeloid proliferative neoplasm with eosinophilia

The 2008 World Health Organization (WHO) classification of tumors of hematopoietic and lymphoid tissues introduced a category for myeloid and lymphoid neoplasms with eosinophilia and abnormalities of PDGFRA, PDGFRB or FGFR1. Many of these patients are responsive to tyrosine kinase inhibitor (TKI) therapy. In this case report, we report a unique case of chronic eosinophilic leukemia with novel t(5;12)(q23-31;p13)/ETV6-ACSL6 gene fusion, in which patient was resistant to TKI therapy. This important finding is a novel addition to the above entity in WHO 2008 classification. The ACSL6 gene encodes a long-chain acyl-CoA synthetase, an enzyme that plays an essential role in lipid metabolism and ATP generation pathways in cells. The ETV6-ACSL6 rearrangement is present in diverse types of hematopoietic malignancies. As yet, it is not clear how ACSL6, a gene involved in fatty acid synthesis, contributes to clonal expansion of myeloid progenitor cells. Therefore, elucidating the contribution of ACSL6 to leukemogenesis may allow the development of novel treatment for those resistant to TKI therapy.