A schematic representation showing the differences in bone homeostasis between normal hematopoiesis and leukemia. In normal hematopoiesis (left side of figure), hematopoietic stem cells (HSCs; pink) are in balance with components of the hematopoietic microenvironment including osteoblastic cells (blue), osteoclasts (gray), mesenchymal cells, and vascular structures (background; red). In leukemia (right side of figure), invasion of leukemia cells (purple) results in osteopenia mediated by an expansion of osteoclasts causing increased bone resorption and a concomitant reduction of osteoblastic activity. The effect, if any, on other components of the HSC niche has yet to be determined. Artwork produced by Ms M. Kersting (QIMR).