Immunophenotypic analysis of bone marrow B lymphocyte precursors (hématogones) by flow cytometry.

The aims of this flow cytometry study were to quantify B lymphoid precursors known as hématogones across age and clinical conditions and to study the immunophenotypic profile of these benign immature B cells. A total of 406 consecutive marrow specimens were analyzed for hématogones using 4-color flow cytometry during a 19 month period (60% males and 40% females). The age range was 3 months to 89 years. Hématogones were present in 80% of the specimens. Morphologic analysis of the smears from each patient showed small numbers of hématogones (<13% of total cellularity). The B cell population was defined by CD19 + CD45 bright positivity, coexpression of other B lineage markers: CD20, CD22, CD10, CD29, CD38 and CD58 in addition to HLA-DR and CD34. In our study we found a significant decline in hématogones with increasing age but a broad range was found at all ages. Marrow from some adults contained relatively high numbers. Diagnosis in these patients included cytopenias, infections, and neoplastic diseases. Distinction of hématogones is critical for disease management particularly after therapy of paediatric B acute lymphoblastic leukaemia to monitor for minimal residual disease.