Fluorine-18 fluorodeoxyglucose splenic uptake from extramedullary hematopoiesis after granulocyte colony-stimulating factor stimulation

Two patients with sarcoma, one with recurrent osteosarcoma of the spine and the other with metastatic synovial cell sarcoma, were treated with high-do se chemotherapy that produced severe leukopenia. The patients received gran ulocyte colony-stimulating factor (G-CSF) to stimulate the bone marrow (480 mg given subcutaneously twice daily for 5 to 7 days); their responses were seen as a marked increase in peripheral leukocyte count with no change in the erythrocyte or platelet counts. The patients had fluorine-18 fluorodeox ygluclose (F-18 FDG) imaging 24 hours after the end of G-CSF treatment. Dif fusely increased uptake of F-18 FDG was seen in the bone marrow in both pat ients. In addition, markedly increased uptake in the spleen was noted in bo th, indicating that the spleen was the site of extramedullary hematopoiesis . The patients had no evidence of splenic metastases. The first patient had a history of irradiation to the dorsal spine, which was less responsive to G-CSF administration than was the nonirradiated lumbar spine.