A 20-year-old man has an epiphyseal lytic lesion of the distal femur with a thin sclerotic rim, extending to the articular surface. Histology shows oval to polygonal cells with clear or eosinophilic cytoplasm and occasional nuclear grooves; there is no osteoid production. Which is the MOST likely diagnosis?
- A Giant cell tumour of bone
- B Chondroblastoma ✓
- C Clear cell chondrosarcoma
- D Aneurysmal bone cyst
Correct answer: B. Chondroblastoma
Explanation
Chondroblastoma characteristically occurs in the EPIPHYSIS of long bones in skeletally immature patients (10–25 years). Histologically it shows round/oval cells with coffee-bean (grooved) nuclei and scattered chicken-wire calcification in a chondroid matrix. The cells have clear to eosinophilic cytoplasm. GCT also involves the epiphysis but in older patients (20–40) with giant multinucleated cells as the hallmark and no chondroid matrix. Aneurysmal bone cyst has blood-filled spaces. Clear cell chondrosarcoma is extremely rare and shows clear cells with cartilaginous matrix.
Reference: Maheshwari Essential Orthopaedics, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.