This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Giant Cell Tumor (GCT) or Osteoclastoma, Subject name: Orthopaedics
[{'content': "X. Ray wrist showing soap bubble appearance in epiphyseal region. Diagnosis: \nSelect and explain. \nA. Giant cell tumour', B. Osteosarcoma, C. Osteochondroma, D. Osteoid osteoma", 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. (a) Giant cell tumourRef: Maheshwari 5th ed. 1237; Orthopedic Pathology byVincent J Vigorita P 294* GCT is an epiphyseal tumor* GCT usually involves subarticular region distal radius and distal femur, the proximal tibia being most common site.* If there is a soap bubble appearance in diaphyseal region, it is adamantioma.Also Know* Sun burst appearance: Osteosarcoma* Nidu/Seed in cortex: Osteioid osteoma* Onion skin appearance: Ewing s sarcoma* Exostosis (cartilage cap): Osteochondroma', 'role': 'assistant'}]