Utility of a Simple and Robust Flow Cytometry Assay for Rapid Clonality Testing in Mature Peripheral T-Cell Lymphomas.

OBJECTIVES: Flow cytometry immunophenotyping is limited by poor resolution of T-cell clones. A newly described antibody was recently used to distinguish normal peripheral blood T cells from malignant T-cell clones. Here, we evaluate this antibody as a new diagnostic tool for detecting T-cell clonality in mature peripheral T-cell lymphomas. METHODS: Immunostaining for the T-cell receptor ß chain constant region 1 (TRBC1) along with routine T-cell markers was performed on 51 peripheral blood and two bone marrow samples submitted to the flow cytometry laboratory for suspected T-cell malignancy. RESULTS: TRBC immunophenotyping identified malignant T-cell clones with 97% sensitivity and 91% specificity. Findings correlated with molecular T-cell clonality testing. In cases with equivocal molecular results, TRBC1 immunophenotyping provided additional diagnostic information. CONCLUSIONS: TRBC1 flow cytometric immunophenotyping is a robust and inexpensive method for identifying T-cell clonality that could easily be incorporated into routine flow cytometric practice.

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 Patterns of CD200 and CD1d Expression Distinguish CD10-Negative, CD5-Negative Mature B-Cell Lymphoproliferative Disorders.

OBJECTIVES: The importance of distinguishing mature B-cell lymphoproliferative disorders (B-LPDs) is highlighted by the distinct treatments used for and varying prognoses seen in association with these different diseases. Immunophenotyping allows for accurate and efficient differentiation of many B-LPDs. Recently, we showed that CD200 is highly expressed in hairy cell leukemia (HCL) but not in marginal zone lymphoma (MZL), lymphoplasmacytic lymphoma (LPL), or hairy cell leukemia-variant (HCL-v). Here, we assessed the usefulness of a flow cytometric panel combining CD200 and CD1d with CD25, CD103, and CD11c to distinguish CD10-, CD5- B-LPDs. METHODS: We analyzed the expression of CD200 and CD1d by flow cytometric analysis in 79 cases of CD10-, CD5- mature B-LPDs. RESULTS: Distinct patterns of CD200 and CD1d expression were seen in the examined B-LPDs. HCL showed bright positivity for CD200 along with positive staining for CD1d, whereas HCL-v showed low levels of expression for both markers. LPL demonstrated positive staining for CD200 in combination with dim to negative staining for CD1d. In contrast, MZL was commonly positive for CD1d and negative for CD200. CONCLUSIONS: Flow cytometric analysis of CD200 and CD1d, along with CD25, CD103, and CD11c, can aid in the diagnosis of CD10-, CD5- mature B-LPDs.