Leukemia/lymphoma in control group.

A sagittal section is shown of the sternum of mouse A21. This mouse was treated for 64 days with the vehicle and then killed when terminally ill. A homogeneous infiltration of the bone marrow and the surrounding muscular tissue is seen with intermediate-sized lymphoid cells with round nuclei, large central nucleolus, immature chromatin pattern, and a scant rim of cytoplasm representing pre-B leukemic cells.