Use of a Blast Dominance-Hematogone Index for the Flow Cytometric Evaluation of Myelodysplastic Syndrome (MDS).

OBJECTIVES: We tested whether combined flow cytometric assessment of loss of blast heterogeneity and decreased hematogones is a diagnostically useful approach for evaluation of myelodysplastic syndrome (MDS). METHODS: Bone marrow samples from patients with known MDS were analyzed by 10-color flow cytometric immunophenotyping and compared with normal bone marrow samples. RESULTS: There was loss of blast heterogeneity in patients with MDS compared with normal bone marrow samples, based on the relative size of the dominant blast population (83.0% vs 64.8%) and fewer hematogones (0.08% vs 1.39%). The size of the largest blast population divided by the fraction of hematogones (blast dominance-hematogone [BDH] index) was significantly larger in MDS compared with normal cases (27,084 vs 190, P < .0001; receiver operating characteristic area under the curve = 0.96). CONCLUSIONS: The BDH index is more sensitive and specific than loss of blast heterogeneity or decrease in hematogones for detecting MDS in bone marrow samples and may be useful in clinical practice.

Flow cytometric minimal residual disease assessment of peripheral blood in acute lymphoblastic leukaemia patients has potential for early detection of relapsed extramedullary disease.

OBJECTIVES: To evaluate peripheral blood (PB) for minimal residual disease (MRD) assessment in adults with acute lymphoblastic leukaemia (ALL). METHODS: We analysed 76 matched bone marrow (BM) aspirate and PB specimens independently for the presence of ALL MRD by six-colour flow cytometry (FC). RESULTS: The overall rate of BM MRD-positivity was 24% (18/76) and PB was also MRD-positive in 22% (4/18) of BM-positive cases. We identified two cases with evidence of leukaemic cells in PB at the time of the extramedullary relapse that were interpreted as MRD-negative in BM. CONCLUSIONS: The use of PB MRD as a non-invasive method for monitoring of systemic relapse may have added clinical and diagnostic value in patients with high risk of extramedullary disease.

CD200 flow cytometric assessment and semiquantitative immunohistochemical staining distinguishes hairy cell leukemia from hairy cell leukemia-variant and other B-cell lymphoproliferative disorders.

OBJECTIVES: To evaluate CD200 expression in B-cell proliferative disorders. METHODS: We analyzed 180 recent specimens of B-cell neoplasms for CD200 expression by flow cytometric immunophenotypic analysis, which is better able to assess relative intensity of staining than immunohistochemical staining. RESULTS: We found that hairy cell leukemia exhibits a high level of staining for CD200 in comparison to other B-cell lymphoproliferative disorders, including hairy cell leukemia-variant (HCL-V), marginal zone lymphoma, and lymphoplasmacytic lymphoma. We confirmed this observation by semiquantitative immunohistochemical staining. CONCLUSIONS: Assessment of the CD200 expression level is helpful to distinguish HCL from HCL-V and other B-cell lymphoproliferative disorders and in the differential diagnosis of B-cell neoplasms in general.

High-sensitivity flow cytometric analysis for the evaluation of systemic mastocytosis including the identification of a new flow cytometric criterion for bone marrow involvement.

We used high-sensitivity flow cytometry to assess 93 bone marrow aspirates for involvement by systemic mastocytosis. Aberrant CD2/CD25 expression by CD117-gated mast cells was seen in 34 samples (37%), with the majority of mast cells expressing both markers (n = 23; 68%). In 24 cases, a discrete population of mast cells within the CD117-bright gate correlated with a positive morphologic finding in the biopsy, even in the absence of an aberrant immunophenotype. A discrete CD117-bright population, when considered a positive criterion, increases analytic sensitivity from 77% to 95%, exceeding the sensitivity of morphologic analysis (69% for aspirate and 85% for biopsy). We conclude that flow cytometry is a sensitive and specific test for the presence of systemic mastocytosis, particularly when the presence of a discrete CD117-positive mast cell population is regarded as a diagnostic criterion.