The bone marrow in leukemia is the seat of a diffuse hyperplastic process extending throughout all marrow-containing bones. The spongy trabeculae are destroyed, and the cortex of the long bones becomes thin. On microscopic examination the lesions in bone appear to be due to pressure and growth, local or diffuse, within the bone rather than to loss of blood supply. In some instances there is a direct extension of the leukemic process through the cortex, the periosteum being lifted by the formation of small subperiosteal tumor masses. These masses may extend into the surrounding soft tissues.
Roentgenograms of the skeleton of patients with leukemia show a variable picture. The bones involved in order of frequency are the pelvis, the lumbar vertebrae, the neck of the femur, the head of the humerus and the skull, and less often the metacarpal bones, the ulna, the tibia and the fibula. In the lymphatic