Rare and complex three-way t(8;11;21) translocation in core-binding factor acute myeloid leukemia transforming into refractory mediastinal myeloid sarcoma: cytogenetic and molecular insights.

Core-binding factor (CBF) acute myeloid leukemia (AML) with t(8;21)(q22;q22)/RUNX1::RUNX1T1 is typically considered as a favorable-risk AML in the context of cytarabine-based intensive chemotherapy. However, in some situations such as additional adverse-risk mutations or cytogenetics, the prognosis and disease course may be more uncertain. Here, we report the case of a young patient diagnosed with CBF-AML and RUNX1::RUNX1T1 fusion gene, carrying a rare and complex three-way t(8;11;21)(q22;q13;q22) translocation, with mutated KIT, ASXL1 and TET2 genes, transforming into an aggressive and multi-refractory mediastinal myeloid sarcoma. This case illustrates that this scarcely reported variant might negatively impact the favorable prognosis of CBF-AML.