A 16-year-old boy has dull constant pain in the lower back with mild scoliosis. CT shows a 3.5 cm expansile lytic lesion arising from the right L4 pedicle and lamina with a thin shell of reactive bone. Pain is only partially relieved by aspirin. The most likely diagnosis is:

• A Osteoblastoma ✓
• B Osteoid osteoma
• C Aneurysmal bone cyst
• D Giant cell tumour of bone

Explanation

Osteoblastoma is histologically similar to osteoid osteoma but is larger than 2 cm, arises most often in the posterior elements of the vertebral column, causes local pain rather than classic nocturnal pain relieved dramatically by NSAIDs, and may present with scoliosis when spinal. B lesion under 2 cm in a long bone diaphysis with dramatic aspirin response defines osteoid osteoma, which kills option B. ABC lacks the osteoid-forming stroma and GCT does not favour the neural arch.

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.