Osteoblastoma

Overview

• Rare, benign bone tumor of osteoblastic origin
• Histologically similar to osteoid osteoma, but larger and can be more aggressive
• Most common in adolescents and young adults

Key Features

• Size: >2 cm (osteoid osteoma <2 cm)
• Location:
  • Cortical based lesion
  • Prefers
    • Posterior elements of spine (esp. lumbar)
    • Long bones of lower extremities (femur, tibia)
• Pain: Dull, less nocturnal, less NSAID-responsive than osteoid osteoma

Imaging

General

• Expansile, lytic lesion; may have central nidus and surrounding sclerosis
• Can have cortical breach, soft tissue extension, and aggressive appearance
  X-ray:
• Lytic, expansile, sometimes with thin sclerotic rim; may see matrix mineralization
  CT:
• Defines nidus, bony expansion, internal calcifications
  MRI:
• Disproportionately extensive marrow and soft tissue edema, extending well beyond actual tumor margin (not soft tissue extension like in osteosarcoma or osteomyelitis)
  Bone scan:
• Intense uptake (hot lesion)

Differential diagnosis