A vertebral mass in an otherwise well child which has no matrix mineralization / ossification has a relatively limited differential including:
- benign
- eosinophilic granuloma
- aneurysmal bone cyst: fluid fluid levels would be typical
- giant cell tumor
- malignant
Given the clearly aggressive interface with bone, which is destroyed, a malignancy was unfortunately the most likely diagnosis in this case, and Ewing's sarcoma the most likely entity.