Blast crisis

Blast crisis may be discovered incidentally on complete blood count or when assessing patients with symptoms and signs such as fever, fatigue, malaise, weight loss, anemia, thrombocytopenia, or splenomegaly.

Complete blood count with differential is the initial laboratory test. Cytopenias and the presence of blast cells serve as clues to diagnosis. These should lead to a peripheral blood smear and bone marrow examination.

Diagnosis is confirmed by the percentage of blast cells in the peripheral blood and/or bone marrow (i.e., ≥20% or ≥30% depending on the criteria used) or the presence of an extramedullary proliferation of blasts. Any increase in lymphoblasts in peripheral blood and/or bone marrow indicates lymphoid blast crisis.

Diagnosis of chronic myeloid leukemia (CML) requires the presence of the Philadelphia chromosome (a genetic mutation that results in the oncogenic BCR::ABL1 fusion gene).

Tyrosine kinase inhibitors (TKIs) are paramount in treatment, often used in combination with chemotherapy. Allogeneic stem cell transplant must follow due to rapid relapse.

Blast crisis refers to the transformation of CML from the chronic or accelerated phase to the blast phase.

The blast phase of CML is diagnosed by the percentage of blast cells in the peripheral blood and/or bone marrow, or the presence of an extramedullary accumulation of blast cells, or large foci or clusters of blasts in the bone marrow biopsy. Any increase in lymphoblasts in peripheral blood and/or bone marrow indicates lymphoid blast crisis.[1]Khoury JD, Solary E, Abla O, et al. The 5th edition of the World Health Organization classification of haematolymphoid tumours: myeloid and histiocytic/dendritic neoplasms. Leukemia. 2022 Jul;36(7):1703-19. https://www.nature.com/articles/s41375-022-01613-1 http://www.ncbi.nlm.nih.gov/pubmed/35732831?tool=bestpractice.com ​​[2]National Comprehensive Cancer Network. NCCN clinical practice guidelines in oncology: chronic myeloid leukemia [internet publication]. https://www.nccn.org/guidelines/category_1 [3]Arber DA, Orazi A, Hasserjian RP, et al. International consensus classification of myeloid neoplasms and acute leukemias: integrating morphologic, clinical, and genomic data. Blood. 2022 Sep 15;140(11):1200-28. https://ashpublications.org/blood/article/140/11/1200/485730/International-Consensus-Classification-of-Myeloid http://www.ncbi.nlm.nih.gov/pubmed/35767897?tool=bestpractice.com ​

CML is defined by the presence of the Philadelphia chromosome.[4]Smith G, Apperley J, Milojkovic D, et al; British Society for Haematology. A British Society for Haematology guideline on the diagnosis and management of chronic myeloid leukaemia. Br J Haematol. 2020 Oct;191(2):171-93. https://onlinelibrary.wiley.com/doi/10.1111/bjh.16971 http://www.ncbi.nlm.nih.gov/pubmed/32734668?tool=bestpractice.com