Although intralesional calcification is a common finding of synovial sarcoma, ossification is
an unusual phenomenon in such a soft tissue sarcoma. Here we report a case of ossifying
synovial sarcoma arising in the back of a young adult man. Microscopically, the tumor was
composed of spindle or oval cells together with foci of atypical polygonal cells in small nests
or cord-like structures, displaying an epithelial appearance. In addition, extensive osteoid or
woven bone formation was present in the tumor, resembling extraskeletal osteosarcoma …