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Category: Immunology
Acute Myeloid Leukemia: Diagnosis and Minimal Residual Disease Detection by Flow Cytometry, Page 1 of 2
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Flow cytometry is an integral tool in both the diagnosis and posttherapy evaluation of acute myeloid leukemia (AML). The strength of the technology is its capacity for rapid, sequential single-cell analysis with simultaneous evaluation of multiple antigens, thus providing a comprehensive immunophenotype for discrete cellular subpopulations. As a result, it has become the methodology of choice for determining blast lineage and immunophenotype. Cytochemical or immunohistochemical evaluation, although useful and even required in some settings, has been surpassed by flow cytometry for the evaluation of blood and marrow in most instances (1, 2). Nevertheless, flow cytometric findings must be used in conjunction with morphology, molecular, and cytogenetic findings for the complete diagnosis and subclassification of AML. Evaluation of posttherapy samples for residual acute myeloid leukemia allows enumeration of blasts as low as 1% by morphology; however, distinguishing normal or regenerating progenitors from leukemic blasts rarely can be performed by morphologic examination alone. Flow cytometry not only allows a more sensitive assay, in some cases reaching a sensitivity of 0.01% (3–5), it is also able to identify aberrancies on the leukemic blast population that allow discrimination from normal or regenerating progenitors (2, 6, 7). These attributes make flow cytometry an ideal method for evaluating for minimal residual disease (MRD) in the posttherapy setting.
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Example dot plots of normal, early stem cells (purple) and normal CD34-positive blasts (red). Upper left dot plot shows CD45 versus side scatter (blue: lymphocytes; pink: monocytes; green: maturing granulocytes; aqua: hematogones) with circled area defining the blast region. Remaining dot plots are selectively displaying CD34-positive progenitors only. Myeloid progenitors show increasing expression of CD13, CD33, CD117, and HLA-DR.
Example dot plots of normal, early stem cells (purple) and normal CD34-positive blasts (red). Upper left dot plot shows CD45 versus side scatter (blue: lymphocytes; pink: monocytes; green: maturing granulocytes; aqua: hematogones) with circled area defining the blast region. Remaining dot plots are selectively displaying CD34-positive progenitors only. Myeloid progenitors show increasing expression of CD13, CD33, CD117, and HLA-DR.
Example dot plots of acute myeloid leukemia (red). Upper left dot plot shows CD45 versus side scatter with blast population highlighted in red. Remaining dot plots are selectively displaying CD34-positive leukemic blasts only. Notice, compared to normal myeloid blasts in Fig. 1 , these abnormal, leukemic blasts demonstrate lower side scatter, variably increased CD13, early/abnormal expression of CD15, decreased to absent CD33, variably increased CD34, variably decreased CD45, variably increased CD117, and variably decreased HLA-DR.
Example dot plots of acute myeloid leukemia (red). Upper left dot plot shows CD45 versus side scatter with blast population highlighted in red. Remaining dot plots are selectively displaying CD34-positive leukemic blasts only. Notice, compared to normal myeloid blasts in Fig. 1 , these abnormal, leukemic blasts demonstrate lower side scatter, variably increased CD13, early/abnormal expression of CD15, decreased to absent CD33, variably increased CD34, variably decreased CD45, variably increased CD117, and variably decreased HLA-DR.
Example dot plots of minimal residual disease (MRD; purple population visualized on CD34 gating) with associated regenerating normal myeloid blasts (red). Upper left dot plot shows CD45 versus side scatter (blue, lymphocytes; pink, monocytes; green, maturing granulocytes; aqua, hematogones) with circled area defining the blast region. Remaining dot plots are selectively displaying emphasized, CD34-positive progenitors only. The MRD-positive population (purple) shows abnormal expression of CD4, decreased to absent CD13, uniform CD33, increased CD34, absent CD38, increased CD45, and subset CD56 (not shown) with normal expression of CD117 and HLA-DR and normal lack of CD15. Although the total CD34-positive population accounted for 2% of the white cells, the abnormal, MRD-positive population accounted for 0.03% of the white cells.
Example dot plots of minimal residual disease (MRD; purple population visualized on CD34 gating) with associated regenerating normal myeloid blasts (red). Upper left dot plot shows CD45 versus side scatter (blue, lymphocytes; pink, monocytes; green, maturing granulocytes; aqua, hematogones) with circled area defining the blast region. Remaining dot plots are selectively displaying emphasized, CD34-positive progenitors only. The MRD-positive population (purple) shows abnormal expression of CD4, decreased to absent CD13, uniform CD33, increased CD34, absent CD38, increased CD45, and subset CD56 (not shown) with normal expression of CD117 and HLA-DR and normal lack of CD15. Although the total CD34-positive population accounted for 2% of the white cells, the abnormal, MRD-positive population accounted for 0.03% of the white cells.
Antigens commonly evaluated in the diagnosis of acute myeloid leukemia
Antigens commonly evaluated in the diagnosis of acute myeloid leukemia
Immunophenotypic characteristics associated with certain AML subtypes
Immunophenotypic characteristics associated with certain AML subtypes