Whole exome sequencing analysis of a patient with myeloid/lymphoid neoplasms with eosinophilia and tyrosine kinase gene fusions with ETV6::LYN fusion gene

ETV6::LYN fusion gene is recognized as one of the genetic alterations responsible for myeloid/lymphoid neoplasms with eosinophilia and tyrosine kinase gene fusions (MLN-TK) according to the 2022 WHO classification. However, the clinical features and pathogenesis of MLN-TK with ETV6::LYN are not well defined because of the rarity of the disease. Here, we report an MLN-TK patient with ETV6::LYN that manifested as myeloproliferative neoplasms (MPN) with eosinophilia, myelofibrosis, and T-lymphoblastic lymphoma (T-LBL), which eventually led to acute myeloid leukemia. Targeted RNA sequencing of both lymph node specimens diagnosed with T-LBL and bone marrow specimens diagnosed with MPN specimens detected an identical ETV6::LYN fusion gene. Whole exome sequencing (WES) detected several identical missense and nonsense mutations in both specimens. Detected mutations were not found to be relevant to pathogenesis of T-LBL and MPN in previous reports and were considered variants of uncertain significance. Based on the WES results, ETV6::LYN fusion gene was considered the driver gene essential for the pathogenesis of MPN-TK with ETV6::LYN.