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CMML Transformation — RACP Adult Medicine MCQ

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ModerateHaematologyCMML TransformationRACP Adult Medicine

A 55-year-old man with chronic myelomonocytic leukaemia (CMML) develops splenomegaly and worsening cytopaenias. His bone marrow shows 12% blasts. According to WHO classification, what is the blast threshold for transformation to acute myeloid leukaemia?

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Correct answer: B — ≥20% blasts

According to the WHO classification, the threshold for transformation from MDS or CMML to AML is ≥20% blasts in the bone marrow or peripheral blood. With 12% blasts, this patient has CMML-2 (10–19% blasts) but has not yet transformed to AML. However, this represents high-risk disease requiring treatment consideration. Hypomethylating agents (azacitidine) are first-line for higher-risk MDS/CMML. Allogeneic stem cell transplant is the only curative option.

Reference: eTG – 2025 – Haematology; WHO – 2022 – Haematolymphoid Tumour Classification