This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metastatic Bone Disease, Subject name: Orthopaedics
[{'content': 'A classical expansile lytic lesion in the transverse process of a vertebra is seen in: \nSelect and explain. \nA. Osteosarcoma, B. Aneurysmal bone cyst, C. Osteoblastoma, D. Metastasis', 'role': 'user'}, {'content': 'Answer: B \nExplanation: (b) Aneurysmal bone cystLytic Lesion in Posterior Element of Vertebrae (i.e. spinous process, transverse process, and pedicle) Expansile and Purely lytic, Aneurysmal Bone Cyst, Non-expansile and partly or extensively ossified, Osteoblastoma Body of vertebra is involved in GCT', 'role': 'assistant'}]