• Osteoblastoma is a Benign but Aggressive tumor of Bone (It can attain a large size and is not self-limiting).

Epidemiology

  • 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

Clinical Evaluation

  • 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.

Imaging Evaluation

Radiographic Imaging:

  • Views:
    • Anterior-posterior AP and lateral views of the affected area.
  • Findings include:
    1. The classic appearance of a mineralized central nidus (> 2cm) with a surrounding radiolucent halo and reactive sclerosis.
    2. The lesion may be purely radiolucent, sclerotic, or mixed.
    3. Lesions may be diaphyseal or metaphyseal, and they may be primarily cortical or intramedullary.
    4. 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.

Histology

  • 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

  1. Osteosarcoma.
  2. Aneurysmal Bone Cyst.
  3. Osteomyelitis.
  4. Osteoid osteoma.
Osteoid osteomaOsteoblastoma
Lesion Size< 2 cm> 2 cm
Common locationLong bone diaphysisPosterior elements of the spine
Progressive HistorySelf-LimitedProgressive
HistologyBenign appearance.
No growth potential.
Central nidus composed of more organized osteoid and lined by osteoblasts.
Benign appearance.
Localized growth, with aggressive potential.
Central lesion less organized, with greater vascularity.
Management of Spine LesionsNonsurgical management is indicated as first-line treatment.Surgery is always indicated as they do not respond to nonsurgical treatment.
Osteoid osteoma VS Osteoblastoma

Differentiation between osteoblastoma and aggressive osteoblastoma

OsteoblastomaAggressive Osteoblastoma
Size– Benign.
– More than 1.5 cm.
– Borderline between osteoblastoma and osteosarcoma More than 4 cm
CytomorphologyOsteoblasts 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

  • 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.