Abstract
Normal precursor B cells or hematogones share morphologic and immunophenotypic similarities with lymphoblasts of precursor B-lymphoblastic leukemia. The numbers are often increased and difficult to distinguish in many patients following chemotherapy for precursor B-lymphoblastic leukemia. The purpose of this study was to establish a unique method for differentiating hematogones from lymphoblasts by evaluating the immunofluorescence pattern of nuclear terminal deoxynucleotidyl transferase (TdT) staining in 29 cases of TdT+ acute leukemia and 20 cases with increased numbers of hematogones. All 29 cases of TdT+ acute leukemia demonstrated a finely granular pattern of TdT immunofluorescence that was uniformly distributed in the nucleus, whereas all 20 cases with increased hematogones demonstrated a coarsely granular or speckled pattern of TdT immunofluorescence, which often intensely aligns the nuclear membrane. The nuclear pattern of immunofluorescence using antibodies to TdT is an effective method for distinguishing hematogones from leukemic blasts.
Highlights
Normal precursor B cells or hematogones share morphologic and immunophenotypic similarities with lymphoblasts of precursor B-lymphoblastic leukemia
We describe the application of a simple indirect immunofluorescence test for terminal deoxynucleotidyl transferase (TdT) that can be reliably used to distinguish normal precursor B cells, or hematogones, from leukemic blasts
Nuclear TdT Immunofluorescence Pattern The nuclear pattern of TdT immunoreactivity was evaluated by 4 hematopathologists (M.T.H., J.A.D., B.J.S., and W.N.R.) in 5 high-power fields
Summary
Normal precursor B cells or hematogones share morphologic and immunophenotypic similarities with lymphoblasts of precursor B-lymphoblastic leukemia. The numbers are often increased and difficult to distinguish in many patients following chemotherapy for precursor B-lymphoblastic leukemia. The purpose of this study was to establish a unique method for differentiating hematogones from lymphoblasts by evaluating the immunofluorescence pattern of nuclear terminal deoxynucleotidyl transferase (TdT) staining in 29 cases of TdT+ acute leukemia and 20 cases with increased numbers of hematogones. In patients with precursor B-lymphoblastic leukemia, distinguishing normal precursor B cells from a residual leukemic blast population following chemotherapy may be problematic, frequently requiring multiparameter flow cytometric analysis. We describe the application of a simple indirect immunofluorescence test for terminal deoxynucleotidyl transferase (TdT) that can be reliably used to distinguish normal precursor B cells, or hematogones, from leukemic blasts
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