An 18-year-old male has chronic dull back pain, worse at night, only partially relieved by NSAIDs. CT shows an expansile osteolytic lesion larger than 2 cm in the posterior element of a lumbar vertebra, with reactive sclerosis but no soft tissue mass. Which feature best distinguishes this tumour from osteoid osteoma?

• A Production of prostaglandin E2 causing nocturnal pain
• B Size greater than 2 cm and tendency for progressive enlargement ✓
• C Location in the posterior elements of the spine
• D Benign nature and lack of any recurrence risk

Explanation

Osteoblastoma is histologically similar to osteoid osteoma but exceeds 2 cm in size and progressively enlarges rather than remaining static, hence the old name 'giant osteoid osteoma'. Both produce PGE2-mediated nocturnal pain and both favour the posterior elements of the spine, so these features do not discriminate. Osteoblastoma also has a significant rate of recurrence after curettage and rarely behaves aggressively, unlike osteoid osteoma.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.