Passive movement of radioactive microspheres from bone and soft tissue in an extremity

Bone biopsy is the definitive method for bone tumor diagnosis. Unfortunately, the procedure is not without risk and may substantially increase the rate and extent of tumor cell metastasis. This study used radioactive microspheres (15 micron diameter) to explore the spread of cell-sized particles from the distal femur into the lymphatic system, venous drainage, and local tissue following a simulated biopsy in the canine model procedure. In the initial group of test animals the microspheres rapidly moved from the femur through the venous system to the lungs. There was no movement from the femur into the lymphatic system within 4 days. The lungs effectively filtered the 15 micron microspheres, thus preventing arterial dissemination. Additional groups were used to explore the movement of the cell-sized particles from the soft tissue surrounding the bone. At the end of the 4 day experimental period, microspheres were found in the iliac lymph nodes in two of nine animals. Microspheres were not detected in the lungs of any of these nine animals. These results suggest that tumor cell-sized particles can move rapidly from the bone venous system to the lungs following a bone biopsy. It appears that the lymphatic system does not contribute to this rapid dissemination. However, the role of lymphatics in a more chronic process remains unclear.