High-Grade Primary Osteosarcoma of the Thoracic Spine Presenting as an Ivory Vertebra

We report a 12-year-old Chinese girl with high-grade osteosarcoma of the thoracic spine, a rare site for a rare tumour. Radiograph showed a dense T9 vertebral body resembling an ivory vertebra. Bone scintigraphy revealed abnormal tracer uptake in the T9 vertebral body and posterior elements. Magnetic resonance imaging showed T1and T2hypointense signal in the T9 vertebral body and the posterior elements, with diffuse enhancement. There was an associated heterogeneously-enhancing paravertebral soft tissue component surrounding the T9 vertebral body and the posterior elements, which extended into the epidural space encasing the thecal sac, spinal cord and bilateral intervertebral foramina. Computed tomography showed patchy but extensive mineralisation of all these soft tissue components. She was treated with T9 corpectomy, cord decompression and posterior instrumentation, followed by chemotherapy, with subsequent clinical improvement. The radiological features and differential diagnosis of thoracic spine osteosarcoma are discussed.