Fig. 6

A 56-year-old woman with misdiagnosed primary benign bone tumors of the right tibia. a Preoperative anteroposterior plain radiographs demonstrate expansile, osteolytic bone destruction without periosteal reactive new bone (yellow arrow). b-d The intraprocedural axial noncontrast CT image (using bone windows) shows that the biopsy needle is inserted into the bone lesion (yellow arrow). The histopathologic biopsy results (d: hematoxylin and eosin, original magnification 40×, e: hematoxylin and eosin, original magnification 100×) diagnosed the bone lesion as a benign fibrous histiocytoma. Immunohistochemical staining: CD163 (+), CD34 (−), CD68 (KP1) (+), Desmin (−), Ki-67 positive rate approximately 2%, S ≤ 100 (−), SATB2 (−), SMA (+), and STAT6 focus (+). However, the surgical histopathology results (f: hematoxylin and eosin, original magnification 40×, g: hematoxylin and eosin, original magnification 100×) of the bone lesion confirmed a diagnosis of osteosarcoma. Immunohistochemistry showed that tumor cells were BCL-2 (focus +), Caldesmon (+), Calponin (+), CD34 (−), CD99 (+), Desmin (−), FLI-1 (focus +), HMB45 (−), Ki-67 (Li: 10%), Muc4 (−), S ≤ 100 (−), SMA (+), SOX-10 (−), STAT6 (−), and SATB2 (+)