- Osteoblastoma is a Benign but Aggressive tumor of Bone (It can attain a large size and is not self-limiting).
- Osteoblastoma is a rare bone forming tumor that represents less than 1% of all bone tumors.
- Mostly occurs in 10 to 30 years old patient.
- Male > female (3:1).
- 40% to 50% of the lesions are located in the posterior elements of the spine.
- Other locations for osteoblastoma include proximal humerus, and hip.
See Also: Osteosarcoma
- The most common symptom is Pain that may be similar to that produced by an osteoid osteoma (worse at night and relieved by nonsteroidal anti inflammatory drugs).
- In the spine, painful scoliosis or neurological deficit may be present.
- In the lumbar spine, signs and symptoms of nerve root compression may be evident, whereas in the thoracic spine, spinal cord compression is more common.
- The tumor usually is slow growing, and symptoms may be present for 1 to 2 years before a diagnosis is made.
- Anterior-posterior AP and lateral views of the affected area.
- Findings include:
- The classic appearance of a mineralized central nidus (> 2cm) with a surrounding radiolucent halo and reactive sclerosis.
- The lesion may be purely radiolucent, sclerotic, or mixed.
- Lesions may be diaphyseal or metaphyseal, and they may be primarily cortical or intramedullary.
- Extension into the soft tissue is rare except in the spine, where soft tissue extension is common.
- CT scan: necessary to fully evaluate lesion.
- Bone scan : hot with intense focal uptake.
- The lesion is look like an osteoid osteoma.
- Fibrovascular stroma appearance with production of osteoid and primitive woven bone.
- Bony trabeculae are lined by a single layer of osteoblasts (may be important in differentiating osteoblastoma from osteosarcoma).
- There is a sharp circumscription and a loose arrangement of the tissue.
- Features favoring a malignant diagnosis include permeation of surrounding tissue and sheets of osteoblasts without bone production.
Differential Diagnosis of Osteoblastoma
|Lesion Size||< 2 cm||> 2 cm|
|Common location||Long bone diaphysis||Posterior elements of the spine|
|Histology||Benign appearance. |
No growth potential.
Central nidus composed of more organized osteoid and lined by osteoblasts.
Localized growth, with aggressive potential.
Central lesion less organized, with greater vascularity.
|Management of Spine Lesions||Nonsurgical management is indicated as first-line treatment.||Surgery is always indicated as they do not respond to nonsurgical treatment.|
Differentiation between osteoblastoma and aggressive osteoblastoma
– More than 1.5 cm.
|– Borderline between osteoblastoma and osteosarcoma More than 4 cm|
|Cytomorphology||– Osteoblasts are round or ovoid with eccentric nuclei and moderate amount of cytoplasm.||– Aspirates are highly cellular, osteoblasts are 2-3 times larger than conventional osteoblasts (epithelioid osteoblasts)|
|Histopathology||– Haphazardly deposited trabeculae of woven bone rimmed by osteoblasts and scattered osteoclasts with in richly vascular stroma.|
– Mitosis rare.
|– Wider and more irregular trabeculae bordered by epithelioid osteoblasts. Mitosis present.|
– High risk of recurrence.
See Also: Differential Diagnosis for Bone Lesions
- Treatment consists of extended curettage or resection.
- Bone grafting of the defect may be necessary.
- In the spine, instrumented fusion may be necessary if resection causes instability.
- Some authors recommend adjuvant radiation therapy for spinal lesions because revision surgery for recurrences in this area is difficult.
- As follow up care, patients should have serial radiographs of the primary site and of the chest.