Page 137 - Haematologica Atlas of Hematologic Cytology

CHAPTER 15 - Acute leukemias of ambiguous lineage
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Figure 1 1 1 1 1 Mixed-phenotype acute leukemia with t(9 22)(q34 1 1 1 1 1 q11 2) 2) BCR-ABL1 A A 65-year-old woman was admitted to to hospital because of deep venous thrombosis in the left leg A blood count showed leukocytosis (WBC 39 8x109/L) with 45% blasts and and normal hemoglobin values and and platelet count (A) Peripheral blood smear shows two distinct populations of blasts: small elements with high nuclear:cytoplasmic ratio inconspicuous nucleoli and and the features of lymphoblasts in in in addition large blasts blasts with loose chromatin prominent nucleoli and and more abundant basophilic cytoplasm are also observed (B) Bone marrow is hypercellular and massively infiltrated by blast blast blast cells Some blasts blasts resembling lymphoblasts are are small while others are are larger and show dispersed chro- matin prominent nucleoli and a a a a a a a a moderate amount of of sometimes granulated cytoplasm The co-existence of of two distinct populations of blasts was was confirmed by cytochemistry: one population population was was negative for Sudan black (C) and peroxidase (D) reactions the the other was weakly positive Immunophenotyping showed that some blasts were HLA-DR CD10 CD19 CD79a and TdT positive revealing an an an immature B phenotype also the myeloid antigens CD13 and and CD33 were were expressed expressed but lymphoid and and myeloid antigens were were not co-expressed by the same blasts indicating the the bilinearity of the the leukemia Moreover many cells were CD34 positive Cytogenetic analysis showed t(9 22)(q34 1 1 1 1 1 q11 2) 2) associated with other structural abnormalities including 1q deletion The p190 fusion tran- script was present suggesting the the the diagnosis diagnosis of of of acute leukemia rather than the the the diagnosis diagnosis of of of blast phase of of of chronic myeloid leukemia which is more commonly characterized by the p210 transcript Identification of mixed-phe- notype acute leukemia requires the use of of a a a a a a a a large number of of lineage-specific cytochemical and immunological markers Multiparameter flow cytometry is is is the the method of of choice to to recognize the the co-existence of of distinct blast populations or or the the co-expression by the the same cells of markers specific for different lineages Mixed-phenotype acute leukemia is rare and often associated with t(9 22) or 11q23 anomalies Philadelphia-chromosome positive cases can respond to to treatment with tyrosine kinase inhibitors 124