Immunophenotypic Characterisation of Blast Crisis in Chronic Myeloid Leukemia : Experience at a Tertiary Care Centre

Aims and Objectives: Chronic myeloid leukemia (CML) is a clonal stem cell disorder that is hallmarked by the presence of a t(9;22), also known as the Philadelphia chromosome. The natural history of CML is typically triphasic: an initial indolent chronic phase, followed by an accelerated phase and usually a terminal, highly aggressive blast phase. Determination of the cell lineage of CML blasts is clinically important for a better response to chemotherapy and longer survival. Hence, it becomes essential to correctly classify the nature of BC preferably by immunophenotyping for further course of management and survival.

Materials and Methods: This study retrospectively analyzed cases of CML-BC for 5 years and lineage of blasts were determined in each case depending upon the expression of markers by comprehensive immunophenotyping on flow cytometry. EDTA peripheral blood samples or bone marrow aspirates were used for immunophenotyping using 19 antibody panels.

Results: 15 cases of CML-BC were reported for 5 years with a male to female ratio of 2:1 and a median age of 38.3 yrs. Flow cytometry revealed 8 cases were of lymphoid BC and 7 cases were of myeloid BC. Blast percentage ranged from 16% to 90%. Aberrant myeloid antigen expression was common in cases with lymphoid BC. Out of 7 cases of myeloid BC, 2 cases of monocytic lineage were seen. CD7 positivity was common in cases with myeloid BC.

Conclusion: Immunophenotyping is important in distinguishing between a myeloid and lymphoid blast crisis, thus providing clinically useful information for further treatment protocols and prognosis.