This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Intracranial Space Occupying Lesion, Subject name: Medicine
Thumb sign on CT head is seen in? 
Select and explain. 
A. Chordoma, B. Metastasis, C. Glioblastoma multiforme, D. Astrocytoma
A: Chordoma
Answer: A: Chordoma 
Explanation: Thumb sign on CT head is seen in Chordoma. Sella Chordoma Presents with bony clivus erosion and local invasion. Calcification also occurs On FNAC- mucinous material obtained