Distinguishing chronic myeloid leukemia in megakaryocytic blast crisis from de novo Ph+ acute megakaryoblastic leukemia: a case report and systematic review.

Chronic myeloid leukemia (CML) with megakaryoblastic blast crisis (MKBC) as the initial manifestation is extremely rare, accounting for less than 3% of all CML cases. Philadelphia chromosome-positive acute myeloid leukemia, FAB M7 subtype (Ph+ AML-M7), is also known as Philadelphia chromosome-positive acute megakaryoblastic leukemia (Ph+ AMKL), representing a distinct and prognostically unfavorable category of AML. Morphologically and immunophenotypically, these two entities are nearly identical, posing significant diagnostic challenges. We describe a novel case of Ph+ leukemia with MKBC differentiation that appears most consistent with CML in blast phase (BP). Following treatment with a tyrosine kinase inhibitor (TKI) combined with induction and consolidation chemotherapy, the patient achieved complete remission (CR). Although hematopoietic stem cell transplantation (HSCT) was declined due to economic constraints, the patient has maintained deep molecular remission(MR5, BCR::ABL1IS ≤ 0.001%)for 35 months to date. Through a systematic review of existing literature, this article elucidates key discriminative features between the two conditions and proposes a practical diagnostic and therapeutic framework to guide clinical decision-making.