Osteoid Osteoma

February 14, 2021 | By : OrthoFixar | Orthopedic Pathology


  • Osteoid osteoma is a self-limiting benign bone tumor.
  • It’s one of three bone tumors in which tumor cells produce osteoid:
    1. Osteoid osteoma
    2. Osteoblastoma
    3. Osteosarcoma.

Epidemiology

  • Most osteoid osteomas occurs in the second or third decades of life (< 30 years old).
  • Male > female (3:1).
  • The tumor usually found in cortical bone, (It can also be found in cancellous bone).
    • Common locations include diaphyseal bone, proximal femur, tibia, and spine.

Clinical Evaluation

  • The patient with an osteoid osteoma has pain that is worsen at night and is relieved by aspirin or other nonsteroidal anti-inflammatory medications (NSAIDs).
    • Maybe due to increased levels of cyclooxygenases and prostaglandins that have been found in the lesion.
  • When the tumor is near a joint, swelling, stiffness, and contracture may occur.
  • May produce painful non-structural scoliosis in adolescent.
    • The Osteoid osteoma found on the side of concavity.
    • This is thought to result from marked para vertebral muscle spasm.

Imaging Evaluation

  • Imaging studies usually are diagnostic.
  • Plain radiographs often are sufficient to make the diagnosis.
    • The lesion consists of a small (<1.5 cm) central radiolucent nidus with surrounding bony sclerosis.
  • Computed tomography CT is the best study to identify the nidus and confirm the diagnosis.
    • It demonstrates better contrast between the lucent nidus and reactive bone.
  • Technetium bone scans always show intense focal uptake.
    • Double density sign which if present is highly specific and helpful in distinguishing it from osteomyelitis.
  • Ultrasound: focal cortical irregularity with adjacent hypoechoic synovitis may be present at the site of intra-articular lesions.
  • MRI usually shows extensive surrounding edema.

The double density sign, also sometimes referred to as the hotter spot within hot area sign. It refers to a central focus of intense uptake (the nidus) within a surrounding lower, but nonetheless increased uptake(the rim).

Histology Findings

  • Fibrovascular tissue with immature bony trabeculae that are rimmed by
    prominent osteoblasts, and surrounded by a sclerotic rim.
  • It’s appears similar to osteoblastoma (osteoblastomas are larger).

The osteoid osteoma is composed of three concentric parts:
1. Nidus
2. Fibrovascular rim
3. Surrounding reactive sclerosis

Differential Diagnosis

  • Long bones lesions differential diagnosis are:
    1. Enostoses (bone island)
    2. Stress fracture.
    3. Osteomyelitis (Brodie abscess).
    4. Cortical desmoid
    5. Osteochondroma
    6. Osteosarcoma
  • Posterior spinal lesions differential diagnosis are:
    1. Aneurysmal bone cyst.
    2. Osteoblastoma.
OSTEOID OSTEOMAOSTEOBLASTOMA
Presentation– Diurnal pain pattern/night pain
– Pain relieved by aspirin/NSAIDs
– Random pain pattern
– Pain not relieved by aspirin/NSAIDs
Imaging– Central radiolucent nidus < 1 cm Large secondary bone reaction
– Characteristic “target” appearance
– Central radiolucent nidus > 2 cm
– Minimal secondary bone reaction gives lesion a more aggressive appearance
LocationDiaphyseal (typical) – Diaphyseal or metaphyseal
– Posterior spine elements
Growth patternSelf-limited growth pattern Unlimited growth pattern
Treatment– Radiofrequency ablation (RFA)
– Surgery if tumor is close to nerve or vessels (e.g., spine)
Intralesional excision
Osteoid Osteoma versus Osteoblastoma

Treatment

Non-Operative treatment:

  • Indications:
    1. The patient’s symptoms are adequately controlled.
    2. The patient is willing to undergo long term medical management.
  • Anti-inflammatory medication can be used as the definitive treatment.
  • Patients treated in this manner usually experience spontaneous healing of the lesion within 3 to 4 years.

Operative treatment:

  1. CT scan–guided RFA:
    • It’s the dominant method of treatment.
    • Indications:
      • Failure of medical management
      • Most patients with lesions of the pelvis or long bones of the extremities.
    • Contraindication:
      • A lesion close to a critical structure (i.e., neurovascular bundle or spinal cord) is a to RFA.
    • A radiofrequency probe is placed into the lesion, and the nidus is heated to 80-90°C.
    • It usually is done as an outpatient procedure, and patients usually can return immediately to full activity.
    • Recurrence rates are less than 10%.
  2. Open surgical removal:
    • Indication:
      • Failure of medical management
      • A lesion close to a critical structure (i.e., neurovascular bundle or spinal cord).
    • Removal of the entire nidus, this can be accomplished by curettage or en bloc resection.
    • Recurrence rates with this technique are less than 10%.
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