Immunophenotypic analysis of hematogones (B-lymphocyte precursors) and neoplastic lymphoblasts by 4-color flow cytometry

Hematogones are identified by 4-color flow cytometry in most bone marrow specimens. They are more commonly found and are generally present in higher numbers in children. There is a general decline in hematogones with increasing age but a broad range exists at all ages and marrow from some adults contains relatively high numbers. They are often increased (>5%) in regenerating marrow and in some clinical conditions, particularly various types of cytopenias and neoplastic diseases. Hematogones may morphologically resemble the neoplastic lymphoblasts of precursor B ALL and their immunophenotype also has features in common with neoplastic lymphoblasts. Distinguishing hematogones from neoplastic lymphoblasts may be problematic in post-chemotherapy and post-bone marrow transplant regenerating marrow. With 4-color flow cytometry using optimal antibody combinations the distinction can nearly always be made. Hematogone populations always exhibit a continuous and complete maturation spectrum of antigen expression typical of the normal evolution of B-lineage precursors; they lack aberrant or asynchronous antigen expression. The neoplastic lymphoblasts in precursor B ALL deviate from the normal B-lineage maturation spectrum and exhibit maturation arrest and over-, under-, and asynchronous expression of antigens observed on normal B-cell precursors and they often aberrantly express myeloid-associated antigens.