A 58-year-old man with known chronic myeloid leukemia on imatinib for 2 years presents with rising WBC, 25% blasts in peripheral blood, and new trisomy 8. Which phase of CML does this represent?

• A Chronic phase
• B Blast phase (blast crisis) ✓
• C Accelerated phase
• D Molecular relapse

Explanation

Blast phase (blast crisis) is defined by ≥20% blasts in peripheral blood or bone marrow, or extramedullary blast proliferation. This patient has 25% blasts, meeting the blast phase criterion. Accelerated phase includes 10-19% blasts, basophils ≥20%, platelets <100,000 unrelated to therapy, or clonal evolution. Trisomy 8 is a clonal evolution finding but the blast count alone defines blast phase. This is the most critical distinction for management.

Reference: WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues, Revised 4th (2017) ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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