This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Orthopaedics
[{'content': 'Chordoma commonly involves -a) Dorsal spineb) Clivusc) Lumbar spined) Sacrume) Cervical spine \nSelect and explain. \nA. bd, B. d, C. ab, D. ac', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Chordoma \n\nChordoma is rare malignant tumor originating from the remanants ofprimitive notochord.\nAs the vertebrae develop, notochord disappears and in adults, the normal remnant of notochord is nucleus pulsosus of the intervertebral disc. In chordoma, this embryonic notochordal foci remains inside the vertebral body and forms tumors.\nIt occurs in adult males after 50 years.\nIt commonly occurs in the sacrococcygeal or in the spheno-occipital regions. Sacrum is the most common site : - Sacrum 50% clivus (35%), cervical thoracic/lumbar (15%).\nMost of them occur in vertebral bodies.', 'role': 'assistant'}]