Application of Multiparameter Flow Cytometry for the Identification of Dysplasia in Granulocytic, Monocytic, and Erythrocytic Lineages and Blasts in Patients with Myelodysplastic Syndromes.

The diagnosis and classification of myelodysplastic syndromes (MDS) are based on cytomorphology (CM) and cytogenetics. A high degree of experience in CM is required to allow the accurate identification of dysmyelopoiesis and quantification of bone marrow blasts. The identification of dysplastic features in all lineages by multiparameter flow cytometry (MFC) has been shown feasible. To further analyze the potential role of MFC in the diagnostic work-up of MDS we analyzed 224 bone marrow samples from patients with suspected of proven MDS by MFC, CM, and cytogenetics in parallel. Blast counts as determined by CM and MFC, respectively, ranged from 0% to 21% (median, 5%) and from 0% to 33% (median, 4%; correlation: r=0.192, p=0.018). The median number of aberrant features detected by MFC were 0 for blasts (range, 0 to 4), 2 for granulocytes (0 to 7), 1 for monocytes (0 to 5), and 0 for erythrocytes (0 to 2). The most frequent dysplastic features observed in the blast populations included aberrant coexpression of CD11b (20.5%), CD15 (14.3%) and CD64 (14.3%). The most frequent dysplastic features observed in the granulocytic cell populations included reduced side-scatter signal corresponding to hypogranulation (71.4%), aberrant coexpression of CD56 (29.0%), aberrant pattern of CD13/CD16 expression (26.3%), aberrant pattern of CD11b/CD16 expression (25.9%), reduced expression of CD64 (17.0%), and aberrant expression of HLA-DR (14.7%). The most frequent dysplastic features observed in the monocytic cell populations included aberrant coexpression of CD56 (31.3%), aberrant coexpression of CD16 (26.3%), an aberrant pattern of CD11b/HLA-DR expression (6.7%), and aberrant coexpression of CD2 (5.8%). The most frequent dysplastic features observed in the erythroid cell populations included an aberrantly strong expression of CD71 and CD235a (23.7%), a lack of CD71 expression (10.7%), and an aberratly homogeneous expression of CD71 (7.1%). The presence of dysplastic features by CM as well as the presence of cytogenetic aberrations tended to be associated with a higher number of dysplastic features by MFC. These data suggest that the identification of dysplastic features by MFC is feasible although there is a large heterogeneity in aberrantly expressed antigens. Thus, a comprehensive panel of antibodies must be applied to allow the detection of dysplasia. Future studies will define the role of MFC in optimizing the diagnosis of MDS in cooperation with CM and cytogenetics.