Fig. 1

Before neoadjuvant chemotherapy. a Plain radiography. Mild cortical irregularity was detected at the ulnar side of the radius. b, c CT: (b) sagittal and (c) axial images (bone condition). A periosteal reaction was detected at the dorsal radius. d, e Gadolinium contrast MRI: (d) axial and (e) coronal images. A huge extraskeletal tumor surrounding the radius was strongly enhanced. f Hematoxylin-Eosin staining of the specimen from open biopsy. Highly dense tumor cells with strong nuclear atypia or atypical mitosis, and tumoral osteoid were detected. No cartilage formation was detected