| Summary: | We report a case of myeloproliferative neoplasm, not otherwise specified (MPN-NOS)-transformed AML with <i>BCR::JAK2</i> rearrangement. Chromosomal analysis indicated a simple abnormal karyotype 46,XY,t(7;17)(q21;q24),t(9;22)(p24;q11.2). Fluorescence in situ hybridization (FISH) using a BCR/ABL1/ASS1 probe set suggested a possible <i>BCR</i> rearrangement and a reflex JAK2 breakapart probe indicated <i>JAK2</i> rearrangement, most likely partnered with <i>BCR</i>. Optical genome mapping (OGM) analysis confirmed <i>BCR::JAK2</i> derived through an inv(9)(p24p13) after a t(9;22)(p13;q11.2) in this case. Due to the complexity of chromosomal aberrations, disruption and/or rearrangement of other genes such as <i>KIF24::BCR</i>, <i>JAK2::KIF24/UBAP1,</i> and <i>CDK6:SOX9</i> were also identified by OGM. Although the functionality and clinical importance of these novel rearrangements were unknown, disruption of these genes might be associated with a poorer response to chemotherapy and disease progression. We also reviewed all cases with <i>BCR::JAK2</i> rearrangement reported in the literature. In conclusion, a suspected t(9;22)/<i>BCR::JAK2</i> rearrangement warrants further characterization with genomic assays such as OGM, whole chromosome sequencing, and RNA sequencing to explore other gene disruptions and/or rearrangements.
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