<prompt> Blast crises CML are characterized by:Blast cells in bloodbone marrow 10Blast cells in blood 20Blast cells absentAll  <response>: Ans. b Blast cells in blood 20. Ref. Harrison, 17th, Chapter 104; 18thChapter 109. ; Robbins, Pathology, 7th, 314, 697CML Disease acceleration is defined by:- Development of increasing degrees of anemia unaccounted for by bleeding or therapy;- Cytogenetic clonal evolution; or- Blood or marrow blasts between 10 and 20,- Blood or marrow basophils 20, or- Platelet count 100,000L. Blast crisis is defined as:- Acute leukemia, with blood or marrow blasts 20.- Hyposegmented neutrophils may appear Pelger-Huet anomaly. Very low leukocyte alkaline phosphatase i.e. LAP score is feature of CML vs. leukemoid reaction. Imatinib is DOC for CML.Blast cells can be classified as myeloid, lymphoid, erythroid, or undifferentiated, based on morphologic, cytochemical, and immunologic features. Occurrence of de novo blast crisis or following imatinib is rare. 