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Chronic myeloid leukemia — USMLE Step 2 CK MCQ

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HardInternal MedicineChronic myeloid leukemiaUSMLE Step 2 CK

A 46-year-old with BCR::ABL1-positive chronic myeloid leukemia treated with a tyrosine kinase inhibitor develops fever, bone pain, anemia, and thrombocytopenia. Bone marrow examination shows 23% myeloblasts. Which phase of disease is present?

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Correct answer: D — Progression of chronic myeloid leukemia to blast phase

Explanation lettering: E = shown as A · D = shown as B · A = shown as D · B = shown as E

A is correct: at least 20% peripheral-blood or marrow blasts defines CML blast phase. B is limited to 10–19% blasts. C requires fewer than 10% blasts and is incompatible with the new cytopenias. D does not account for established BCR::ABL1-positive CML. E is a different lymphoid neoplasm and conflicts with the myeloblast phenotype and known antecedent disease.

Reference: National Cancer Institute PDQ: chronic myelogenous leukemia treatment. https://www.cancer.gov/types/leukemia/hp/cml-treatment-pdq