A 19-year-old man has 8 months of dull nocturnal pain in the neck, poorly relieved by NSAIDs. CT shows an expansile, well-circumscribed lytic lesion measuring 2.5 cm in the lamina of C5 surrounded by reactive sclerosis. The most likely diagnosis is:

• A Osteoid osteoma
• B Osteochondroma
• C Aneurysmal bone cyst
• D Osteoblastoma ✓

Explanation

Osteoblastoma is histologically identical to osteoid osteoma but is distinguished chiefly by size, defined as greater than 2 cm. It favours the posterior elements of the spine, produces dull pain that responds less dramatically to salicylates, and may show local expansion. Osteoid osteoma is smaller than 2 cm, causes night pain classically relieved by aspirin through prostaglandin-mediated mechanisms, and rarely exceeds cortical thickness in this way.

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.