A 12-year-old boy complains of chronic knee pain for 6 months. Radiograph shows a well-defined lytic lesion in the epiphysis of the proximal tibia with a thin sclerotic rim. Biopsy reveals chondroid matrix with characteristic 'chicken wire' calcification around plump cells. What is the diagnosis?
- A Giant cell tumour of bone
- B Chondroblastoma ✓
- C Brodie abscess
- D Eosinophilic granuloma
Correct answer: B. Chondroblastoma
Explanation
Chondroblastoma is a benign cartilaginous tumour occurring in the epiphysis of long bones in skeletally immature patients, typically before physeal closure. Histology shows chondroblasts and chondroid matrix with the classic 'chicken wire' pattern of pericellular calcification. Giant cell tumour is the main distractor, but it occurs after physeal closure and lacks chondroid matrix with chicken wire calcification.
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.