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: Pathology
A 50 year old patient presents with a lesion in the midline involving the sacrum. It is found to be sclerotic. What is the most probable diagnosis ? 
Select and explain. 
A. Metastatic, B. Chordoma, C. Osteosarcoma, D. Chondrosarcoma
B: Chordoma
Answer: B: Chordoma 
Explanation: Ans. is 'b' i.e., Chordoma Sclerotic lesion involving midline in the sacrum is likely to be chordoma. o It occurs most commonly at either end of notochord (midline) in following locations a) Sacrococcygeal region b) Clivus c) Suprasellar region