Recent advances in flow cytometry: application to the diagnosis of hematologic malignancy.

O scatter plot than on traditional forward side-scatter gating (Fig 1). VER A DECADE HAS passed since ‘‘Immunologic Classification of Leukemia and Lymphoma’’ by Foon and Todd was published in Blood. Over this decade, flow Acute myeloid leukemia (AML). AML is traditionally subclassified by morphology and cytochemistry according cytometry has evolved from a promising new technology to an indispensable tool in the diagnosis of hematologic to the French-American-British (FAB) criteria as modified by the National Cancer Institute-Sponsored Workshop that malignancies. Many new antibodies, improved gating strategies, and routine use of multiparameter techniques have draincorporates immunophenotypic data. Although the major role of flow cytometry is to provide immunophenotypic data, matically improved the diagnostic utility of flow cytometry. This review will focus on the use of flow cytometry in cellular morphology can be examined by both forward-side scatter and CD45-side scatter analysis. We will summathe routine clinicopathologic approach to the diagnosis of leukemias and lymphomas, emphasizing the relevant literarize each of the major subtypes of AML below incorporating the morphologic, immunologic, and cytogenetic (MIC) apture of the past 10 years. Some of the recent advances in flow cytometric monitoring of disease and treatment are shown in proach. The ability of flow cytometry to identify myeloid versus the last section. We will review the use of flow cytometry in the diagnosis of major disorders highlighting the prognoslymphoid differentiation approaches 98%. However, the prognostic value of immunophenotypic data is controvertically important subgroups defined either morphologically or genetically. The discussion will focus not only on the use sial. Studies that failed to find prognostic value for immunophenotyping generally looked at the correlation of outof flow cytometry in the differential diagnosis of a particular disorder, but also correlate immunophenotypic, molecular, come with individual antigens and did not find clinically useful associations, although the utility of flow cytometry in and cytogenetic data in the delineation of biologically important subgroups. It is our intent that this review support a defining myeloid differentiation was confirmed. Studies that found correlation with specific phenotypes were genercombined modality approach to the daily practice of hematology-oncology and hematopathology. A working knowlally single institution results. Three of the four studies showing no correlation were in children, in whom there is edge of the basics of flow cytometry is assumed; thus, technical aspects of instrumentation, normal distribution of surface some evidence that the t(8;21) may not carry the same good prognosis as in adults. Additionally, differences in reantigens, and methodologies are not included, but have recently been reviewed. agents, gating and staining techniques, and thresholds for positivity may account for discrepancy. ACUTE LEUKEMIA Correlating clinical outcome with specific antigens rather than the total phenotype is probably not useful. Lymphoid Flow cytometric analysis of acute leukemia is interpretive, antigen expression in AML is associated with both poor, combining the patterns and intensity of antigen expression t(9;22) and 11q23 rearrangements, and favorable, t(8;21), to reach a definitive diagnosis. Gating is critical to isolate t(15;17), and inv(16), prognostic genetic alterations. the abnormal cells because the leukemic phenotype should For example, CD19 expression may be associated with either be determined on as pure a population as possible. Most leukemias involve the analysis of bone marrow. Standard forward and side scatter gating is not optimal for separating From the Departments of Pathology and Laboratory Medicine bone marrow cells because of the overlap between monoand Internal Medicine, Division of Hematology and Oncology, Unicytes, blasts, myelocytes, promyelocytes, and metamyeloversity of Kentucky, College of Medicine, and the Lucille Parker cytes. As bone marrow cells mature, they express increasing Markey Cancer Center, Lexington, KY. CD45. Thus, when CD45 is combined with side scatter, Submitted October 4, 1996; accepted May 28, 1997. which separates lineages based on cytoplasmic complexity, Address reprint requests to Kenneth A. Foon, MD, Markey Cancer the bone marrow sample is readily separated into its cellular Center, Room CC140, 800 Rose St, Lexington, KY 40536-0093. constituents. Infiltration of marrow by immature cells or q 1997 by The American Society of Hematology. 0006-4971/97/9008-0036$3.00/0 blasts is more easily recognized on a CD45 versus side-