Hematogones as an internal control in flow cytometric analysis of suspected acute lymphoblastic leukemia

Hematogones are benign immature B cells that commonly populate the bone marrow of children. Their presence has been noted to interfere with the flow-cytometric analysis of cases of suspected acute lymphoblastic leukemia (ALL) because their immunophenotype (positive for CD19, CD10, CD34, and terminal deoxynucleotidyl transferase) is similar to that of pre-B cell lymphoblasts. Here we report a case in which the presence of a discrete population of hematogones, characterized by low-intensity CD10 cell-surface staining compared with pre-B cell lymphoblasts, actually aided in the recognition of early relapsed ALL and disease progression over a 4-day period. We also review our experience with flow-cytometric immunophenotyping in pediatric cases of suspected leukemia to evaluate the frequency of this occurrence.