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': 'Soap bubble appearance on Xray is seen in which bone tumor - \nSelect and explain. \nA. Osteogenic sarcoma, B. Giant cell tumor, C. Multiple myeloma, D. Chondroblastoma', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. is \'b\' i.e., Giant cell tumor Characteristic radiological features of few bone tumors Celery-stick appearance Enchondromas Coat-hanger appearance Osteochondroma Codman tumor and chicken-wire calcification Chondroblastoma Double density sign on radionuclide scan Osteoid osteoma Nidus and sclerotic rim Osteoid osteoma "Driven snow" appearance Pindborg tumor Fallen fragment/Hinged fragment sign Simple (unicameral) bone cyst "Eggshell" covering of expansile cortex over surface of lesion ABC \'Soap bubble\' appearance ABC Soap bubble appearance (& goes into corners) GCT (Osteoclastoma) \'Floating tooth\' sign Eosinophilic granuloma, adamantinoma Onion skin (onion peel) appearance Ewing sarcoma Skip lesions Osteosarcoma, Ewings sarcoma \'Sunray/Sunburst\' appearance Osteosarcoma String sign (to differentiate from myositis ossificans) Parosteal osteosarcoma Popcorn/mottled calcification Chondrosarcoma Shepherd\'s crook deformity Fibrous dysplasia Codman\'s triangle Osteosarcoma, Ewing sarcoma Winking owl sign Metastasis to pedicles of vertebra Corduroy/accordion vertebra/vertical striations Vertebral hemangioma Polka dot sign on CT Vertebral hemangioma Geographical skull Eosinophilic granuloma Hole-within-a-hole lesion Eosinophilic granuloma', 'role': 'assistant'}]