Q. I’d like to know how to differentiate between acute leukemia and blast crisis of CML.
A. Great question! To diagnose blast crisis (or blast phase) in chronic myeloid leukemia, you need to have one of the following:
- More than 20% blasts in the blood or bone marrow
- An extramedullary focus of blasts (e.g., in the skin, lymph nodes, or spleen)
- A significant focus of blasts in the bone marrow section
Most of the time, blast crisis presents as a straight-up acute leukemia (more than 20% blasts in the blood or bone marrow). So how would you tell blast crisis apart from a de novo acute leukemia?
Well, you could try to find previous material from the patient – an older bone marrow or blood – and see if there is evidence of CML. Or you could look for the BCR-ABL translocation. This translocation (also called the Philadelphia chromosome) is present in all cases of CML (check it out: ALL cases!) and is only present in a very, very small number of acute leukemias (rare cases of acute lymphoblastic leukemia have the Philadelphia chromosome – if you look closely, though, the breakpoint is different).
But assuming you can’t do those things, the best thing to do is look at the remainder of the cells (the non-blasts). In blast crisis, the remainder of the cells would reflect the underlying CML (a case of which is shown above): you’d see a large percentage of neutrophilic cells (with a left shift) and a basophilia. In a regular old acute leukemia, the remainder of the cells would show a normal differential (more neutrophils than lymphocytes, and a very small number of basophils), and no left shift.
- Kristine said Hi Cynthia – Yes!! I totally agree. I remember learning that if you see any secondary granulat...
- Cynthia said I’m going to have agree with the granules being the most important. I’m also MT and I...
- AG said Thanks Kristine, very helpful!
- Frank MD said Succinctly explained. Excellent! Thank you so much!!
- kartik said Thanks,i am learner,when i think hypothtically,i think i may find confusing beetween promyelocyte an...
- Carol said Thanks…. Well explained
- Ulyses Yakovlevich said This looks like an awesome tool for future Pathologists to learn from :).
- Chief said Amazing explanation. No other website teaches this interesting and important medical lesson. Not eve...
- Dr.Kisor Kumar Pal said Very helpful and practical discussion.I learned a lot.
- Cheri said Thank you ! I’m a traveler in Pathology/Histology
- Dr. Syed Mahbub Baksh said During my residency years, I have read only two books: Robbins Pathology and Henry’s Clinical...
- Theresa said Thanks for breaking this down in a simple way to understand it. Well done.