This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bone Tumour, Subject name: Orthopaedics
[{'content': '"Soap bubble appearance" is seen in: \nSelect and explain. \nA. Simple unicameral cyst, B. Aneurismal cyst, C. Giant cell tumour, D. Osteogenic sarcoma', 'role': 'user'}, {'content': 'Answer: C \nExplanation: [Cl (Giant cell tumour): Ref: 181-AGiant c ell tumour"Soap bubble appearance" due to ridging of the surrounding bonesThe appearance of a \'cystic" lesion in mature bone, extending right to the subchondral plate is so characteristic that the diagnosis is seldom in doubt.Aneurysmal bone evst: - well defined radio lucent cyst, often trabeculated and eccentrically placed. It usually docs not extend right upto the articular margin.Osteochondroma: - Large lesions show "cauliflower " appearance with degeneration and calcification in the centre of the cartilage cap.Chondroblastoma: - well demarcated radiolucent area in epiphysisChondromvxoid fibroma: - Rounded or ovoid radio lucent area placed eccentrically in the metaphysis. The endosteal margin may be scalloped, but is almost always bounded by a dense zone of reactive bone extending tongue - like towards the diaphysis.Chondroma (Enchondroma): - Centrally placed radiolucent area at the junction of metaphysis and diaphysis. In mature lesions there are flecks or wisps of calcification within the lucent area (Pathognomic features)Osteoblastoma (Giant osteoid osteoma): well demarcated osteolytic lesion which may contian small flecks of ossification radio isotpe scan will reveal the hot area.Osteoidosteoma: - A small radiolucent area, the so called \'Nidus\' lesion in the diaphysis are surrounded by dense sclerosis and cortical thickening.', 'role': 'assistant'}]