Distances to the endosteum among different groups of cells. (A) Representative histological section from an AML patient in CR. Solid arrows indicated single precursor, arrow head indicated double precursors, and hollow arrow indicated clustered precursor. Dashed red line highlighted the endosteal surface. Staining of sections was done by haematoxilin-giemsa acid fuchsin (HGF), and observed at × 400 magnification. (B) Single and double precursors were located near the endosteum and there was no statistical difference between the two groups. By contrast, the clustered precursors were located further from endosteum than single and double precursors.