On peripheral blood smear of a patient with CML, which finding would indicate blast crisis rather than chronic phase?
- A Basophilia >2%
- B Blasts ≥20% in peripheral blood or bone marrow ✓
- C Splenomegaly on imaging
- D Philadelphia chromosome in >95% of cells
Correct answer: B. Blasts ≥20% in peripheral blood or bone marrow
Explanation
WHO criteria define blast crisis of CML as ≥20% blasts in the peripheral blood or bone marrow, or the presence of extramedullary blast proliferation. Chronic phase CML typically has <2% blasts; accelerated phase has 10–19% blasts, basophils ≥20%, or additional cytogenetic changes. The Philadelphia chromosome is present throughout all phases.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.