Significance of increased proportion of CD10-positive cells in nonmalignant bone marrows of children.

An immunophenotypic pattern characterized by increased proportions of CD10, CD19, and HLA-DR+ cells is observed in the bone marrow of some children with nonmalignant hematologic diagnoses. The purpose of this study was to ascertain the clinical and pathologic significance of this immunophenotype. The morphologic and immunophenotypic results of bone marrow specimens from 23 children with nonmalignant hematologic conditions are presented. In 11 children, an increased percentage of immature B-cell precursors was observed, suggesting the presence of B-lineage malignancy. None of the children have developed malignant lymphoproliferative disease in as long as 4 years of follow-up, despite the demonstration of a clonal lymphocyte proliferation in one patient. Although the biologic significance of the bone marrow immunophenotype is not yet understood, it is important to recognize that this lymphocyte pattern occurs commonly in children with nonmalignant hematologic conditions, and may reflect an increase in normally occurring lymphoid precursor cells.