Blast crisis

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

Full 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.

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

Tyrosine kinase inhibitors 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.[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

CML is defined by the presence of the Philadelphia chromosome.[3]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