The knowledge on the 3rd type hematogones could contribute to more precise detection of small numbers of precursor B-acute lymphoblastic leukemia.

Bone marrow hematogones (benign B-lymphocyte precursors) may cause diagnostic problems due to their morphologic and immunophenotypic similarities with neoplastic lymphoblasts. Hematogone populations in presented study containing 358 bone marrow specimens of 251 individuals always exhibited a continuous and complete maturation spectrum of antigen expression typical for normal evolution of B-lineage precursors; lacking aberrant or asynchronous antigen expression. In contrast lymphoblasts of 19 bone marrows of precursors B-ALL patients showed maturation arrest and exhibited several immunophenotypic aberrancies. Hematogones were identified by 4-color flow cytometry using optimal antibody combinations in many bone marrow samples. They were more commonly found in higher numbers in children, and there was found a general decline in hematogones with increasing age. Bone marrow hematogones were separately assessed as hematogones 1 population of early stage and hematogones 2 of mid-stage precursor B-cells, respectively. In some (about 30%) of hematogones a third type hematogones could be assessed in bone marrow samples. This small B-cell subpopulation was defined by CD10-positivity, coexpressing more mature markers CD19,CD20,CD22 and CD45bright. These cells obviously blended with those of mature B-lymphocytes (CD10-negative) on CD45/SSC, and could be better recognized on CD10-gating. Quantitative immunophenotyping of this study completed the percent antigen expression data in two main hematogone subtypes and lymphocytes in 16 bone marrow specimens and precursor B-ALL lymphoblasts in some samples. Increased information on benign B-lymphocyte precursors, especially that of existence of the 3rd type hematogones could provide a basis for better discrimination of B-leukemia cells even in a very small amounts.