Osteoblastoma

Findings

Figure 1: Axial CT image of the cervical spine with bone windows demonstrates a round, well-defined sclerotic lesion in the right C5 facet.
Figure 2 and Figure 3: Coronal and sagittal MIP CT images demonstrate that the expansile portion of the lesion involves the transverse process, facet and lamina with sparing of the vertebral body.

Differential diagnosis of posterior element lesions
- Aneurysmal bone cyst
- Hemangioma
- Osteoid osteoma/osteoblastoma
- Giant cell tumor


Diagnosis: Osteoblastoma (path proven)


Osteoblastomas are benign osteoid forming lesions which commonly occur in the spine (42%). They are differentiated from osteoid osteomas by their larger size. Osteoblastoma presents as an expansile, geographic lesion with a sclerotic margin occurring in the posterior elements. The lesions may be centered in the pedicle, lamina, transverse or spinous process. Osteoblastomas may exhibit a range of densities varying from a lucent, mixed or blastic appearance. This accounts for the range of appearances on T1 and T2 weighted MR images. Because they are osteoid-forming lesions, osteoblastomas demonstrate increased uptake on bone scan.

Although osteoblastomas usually present with a narrow zone of transition with surrounding sclerosis, they may present with aggressive features with a wide zone of transition and cortical breakthrough. Prostaglandins released by the lesion may cause extensive peritumoral edema. This peripheral inflammatory response may result in periosteal reaction in the adjacent ribs, pleural thickening or effusion and ossification of the ligamentum flavum.

Patients with osteoblastomas usually present in their 2nd to 3rd decade of life (90%). Osteoblastoma is a differential diagnostic consideration of “painful scoliosis.” The most common signs and symptoms include dull pain with scoliosis concave to the side of the lesion. Neurologic symptoms may arise from compression of the cord or nerve roots. Treatment of the lesion involves curettage with bone graft. Occasionally, radiofrequency ablation is used. However, the proximity of the lesion to the cord often limits the use of this treatment. Preoperative embolization is sometimes employed as well.