Abstract: Acute basophilic leukemia (ABL) arising from chronic myeloid leukemia (CML) with abundant mast cells (MCs), coexisting with a complex karyotype is rare. Here, we report an 81-year-old man admitted to our hospital with a history of ABL. He was diagnosed with CML in the chronic phase in January 2018, and Imatinib was used at a daily dose of 400mg. Then, transformation to ABL with abundant MCs in the bone marrow and complex karyotypes including 48,XY, trisomy 8 (+8), isochromosome 17(q10) [i(17)(q10)], and derivative chromosome 22 t(9;22) [der(22)t(9;22)] were discovered simultaneously in January 2022. In conclusion, the increased number of MCs in our case is a reminder that they might play an important role in the prognosis of CML and trigger the development of complex karyotypes. Moreover, this is the first case report of ABL arising from CML with abundant MCs, coexisting with 48,XY, +8, i(17)(q10), and der(22)t(9;22), during Imatinib treatment. Further studies are needed to better characterize this rare condition.
Keywords: CML, TKIs, MCs, ABL, complex karyotype