Multiple diffuse fibrosarcoma of bone associated with extramedullary hematopoiesis.

We report a case of multiple diffuse fibrosarcoma of bone. The patient, a 38-year-old man, was referred to our hospital with knee pain, anemia and thrombocytopenia. No solid mass was seen on radiographic examination of the kneejoint, but magnetic resonance imaging showed hypointensity of the distal femur. Femoral biopsy revealed proliferation of long spindle-shaped fibrosarcoma cells, while a bone marrow biopsy of iliac bone (which appeared normal on radiographic examinations) showed replacement of hematopoietic cells by fibroblast-like spindle cells. A diagnosis of multiple diffuse fibrosarcoma of bone was therefore made. Autopsy revealed tumor invasion into multiple bones and several visceral organs and extramedullary hematopoiesis in the liver, spleen and lymph nodes. As this patient had leukoerythroblastic anemia with poikilocytosis, splenomegaly exhibiting extramedullary hematopoiesis, and apparent fibrotic change in his bone marrow, we suggest that this extremely rare disease should be considered in the differential diagnosis of myelofibrosis.