“Hematogone” is a term used to describe B cell precursors in normal bone marrow. Amazingly, in my nearly 30 years as an immunologist who got his start studying human B cells, I had never come across this term until I recently started researching the origins of leukemias and lymphomas. B cell precursors in normal bone marrow form a constellation of cells that can be identified by flow cytometry using Side Scatter (SSC) vs. CD45 staining. Three major subsets of B cell precursors are easily recognizable. The early B cell precursors have low SSC and low CD45 expression, intermediate stage precursors have intermediate SSC and CD45 expression, and late precursors have the highest levels of SSC and CD45 expression. The pattern formed by these three populations in a 2D flow cytometric plot of SSC vs CD45 is often referred to as “Kentucky Sign” because the pattern resembles the shape of the state of Kentucky.
Differential diagnosis of B cell Acute Lymphoblastic Leukemia (B-ALL) is complicated by these so-called hematogones present in normal bone marrow. Hematogones make up 5-10% of the bone marrow cells in children, and less than 5% in adults, but these numbers can vary. In normal bone marrow hematogones are usually interspersed with more mature B cells, while lymphoblasts in the marrow of B-ALL patients often form large clusters.
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Rimsza LM, Larson RS, Winter SS, Foucar K, Chong YY, Garner KW, and Leith CP. 2000. Benign Hematogone-Rich Lymphoid Proliferations Can Be Distinguished From B-Lineage Acute Lymphoblastic Leukemia by Integration of Morphology, Immunophenotype, Adhesion Molecule Expression, and Architectural Features. Am J Clin Pathol 114:66-75.