Chronic Myeloid Leukemia Unveils Its Dark Side: A Rare Case of Megakaryocytic Blast Crisis.

Chronic myeloid leukemia (CML) can progress from a chronic phase (CP) to an accelerated phase (AP) or an acute leukemia-like blastic phase (BP). However, transformation into a megakaryoblastic phase is very rare, and such a progression is clinically significant due to its poor prognosis and resistance to standard tyrosine kinase inhibitors (TKIs). This report discusses a case of CML that progressed to a megakaryoblastic phase and the patient's death within a month despite receiving one cycle of daunorubicin, cytarabine, and TKI chemotherapy. A 39-year-old female with CML (CP) initially achieved hematological remission with nilotinib but later presented with B symptoms and cytopenias indicative of disease progression. A complete diagnostic workup was performed, including blood counts, bone marrow examination, flow cytometry, fluorescence in-situ hybridization (FISH), and cytogenetic testing. Peripheral blood and bone marrow evaluation confirmed blast crisis with 84% medium to large-sized blasts with basophilic cytoplasm and cytoplasmic blebs. The blasts were positive for CD41 and CD61 by immunohistochemistry (IHC). The blasts also expressed CD45 (dim), CD34, CD33, CD117, CD41, and CD61 by flow cytometry. While BCR-ABL1 positivity is typically associated with CML (90-95%), the additional findings point towards a transformation to acute megakaryoblastic leukemia (AMKL or AML-M7). The rare instance of CML's transformation to AMKL highlights the need for megakaryocytic markers in diagnostic panels to ensure accurate diagnosis and timely, tailored therapies for improved outcomes.

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Human subjects: Consent was obtained or waived by all participants in this study. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work.